[PATCH 0/2] ovl: bugfix for ovl_aio_req

[PATCH 0/2] ovl: bugfix for ovl_aio_req

[yangerkun]

yangerkun (2):
  ovl: factor out ovl_get_aio_req
  ovl: fix UAF for ovl_aio_req

 fs/overlayfs/file.c | 51 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 37 insertions(+), 14 deletions(-)

-- 
2.31.1

[PATCH 1/2] ovl: factor out ovl_get_aio_req

[yangerkun]

Factor out a common function to remove duplicate code in
ovl_read_iter/ovl_write_iter.

Signed-off-by: yangerkun <yangerkun@huawei.com>
---
 fs/overlayfs/file.c | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index d081faa55e83..4ac3cd698c7d 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -282,6 +282,23 @@ static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
 	orig_iocb->ki_complete(orig_iocb, res, res2);
 }
 
+static struct ovl_aio_req *ovl_get_aio_req(struct kiocb *iocb, struct fd *real, int ifl)
+{
+	struct ovl_aio_req *req;
+
+	req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
+	if (!req)
+		return NULL;
+
+	req->fd = *real;
+	real->flags = 0;
+	req->orig_iocb = iocb;
+	kiocb_clone(&req->iocb, iocb, real->file);
+	req->iocb.ki_flags = ifl;
+	req->iocb.ki_complete = ovl_aio_rw_complete;
+	return req;
+}
+
 static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct file *file = iocb->ki_filp;
@@ -304,15 +321,10 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 		struct ovl_aio_req *aio_req;
 
 		ret = -ENOMEM;
-		aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
+		aio_req = ovl_get_aio_req(iocb, &real, iocb->ki_flags);
 		if (!aio_req)
 			goto out;
 
-		aio_req->fd = real;
-		real.flags = 0;
-		aio_req->orig_iocb = iocb;
-		kiocb_clone(&aio_req->iocb, iocb, real.file);
-		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
@@ -364,7 +376,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 		struct ovl_aio_req *aio_req;
 
 		ret = -ENOMEM;
-		aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
+		aio_req = ovl_get_aio_req(iocb, &real, ifl);
 		if (!aio_req)
 			goto out;
 
@@ -372,12 +384,6 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 		/* Pacify lockdep, same trick as done in aio_write() */
 		__sb_writers_release(file_inode(real.file)->i_sb,
 				     SB_FREEZE_WRITE);
-		aio_req->fd = real;
-		real.flags = 0;
-		aio_req->orig_iocb = iocb;
-		kiocb_clone(&aio_req->iocb, iocb, real.file);
-		aio_req->iocb.ki_flags = ifl;
-		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
-- 
2.31.1

[PATCH 2/2] ovl: fix UAF for ovl_aio_req

[yangerkun]

Our testcase trigger follow UAF:

[  153.939147] ==================================================================
[  153.942199] BUG: KASAN: use-after-free in ext4_dio_read_iter+0xcc/0x1a0
[  153.943331] Read of size 8 at addr ffff88803b7f1500 by task fsstress/726
[  153.948182] Call Trace:
[  153.948628]  ? dump_stack_lvl+0x73/0x9f
[  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
[  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
[  153.951693]  ? kasan_report.cold+0x81/0x165
[  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
[  153.953190]  ? __asan_load8+0x74/0x110
[  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
[  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
[  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
[  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
[  153.956916]  ? ovl_read_iter+0x15f/0x270
[  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
[  153.958436]  ? aio_setup_rw+0xbf/0xe0
[  153.959101]  ? aio_read+0x190/0x2d0
[  153.959750]  ? aio_write+0x3e0/0x3e0
[  153.960404]  ? __kasan_check_read+0x1d/0x30
[  153.961167]  ? ext4_file_getattr+0x116/0x1b0
[  153.961978]  ? __put_user_ns+0x40/0x40
[  153.962714]  ? kasan_poison+0x40/0x90
[  153.963384]  ? set_alloc_info+0x46/0x70
[  153.964102]  ? __kasan_check_write+0x20/0x30
[  153.964856]  ? __fget_files+0x106/0x180
[  153.965571]  ? io_submit_one+0xaa7/0x1480
[  153.966325]  ? aio_poll_complete_work+0x590/0x590
[  153.967713]  ? ioctl_file_clone+0x110/0x110
[  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
[  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
[  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
[  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
[  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
[  153.975575]  ? __kasan_check_read+0x1d/0x30
[  153.976749]  ? do_syscall_64+0x35/0x80
[  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
[  153.979436]
[  153.979738] Allocated by task 726:
[  153.980352]  kasan_save_stack+0x23/0x60
[  153.981054]  set_alloc_info+0x46/0x70
[  153.981745]  __kasan_slab_alloc+0x4c/0x90
[  153.982492]  kmem_cache_alloc+0x153/0x750
[  153.983953]  ovl_read_iter+0x13b/0x270
[  153.984689]  aio_read+0x190/0x2d0
[  153.985332]  io_submit_one+0xaa7/0x1480
[  153.986060]  __x64_sys_io_submit+0x125/0x3b0
[  153.986878]  do_syscall_64+0x35/0x80
[  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[  153.988516]
[  153.988824] Freed by task 750:
[  153.989417]  kasan_save_stack+0x23/0x60
[  153.990140]  kasan_set_track+0x24/0x40
[  153.990871]  kasan_set_free_info+0x30/0x60
[  153.991639]  __kasan_slab_free+0x137/0x210
[  153.992390]  kmem_cache_free+0xf8/0x590
[  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
[  153.994205]  ovl_aio_rw_complete+0x31/0x60
[  153.995043]  iomap_dio_complete_work+0x4b/0x60
[  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
[  153.996742]  bio_endio+0x40d/0x440
[  153.997376]  blk_update_request+0x38f/0x820
[  153.998160]  scsi_end_request+0x56/0x320
[  153.998872]  scsi_io_completion+0x10a/0xb60
[  153.999655]  scsi_finish_command+0x194/0x2b0
[  154.000464]  scsi_complete+0xd7/0x1f0
[  154.001184]  blk_complete_reqs+0x92/0xb0
[  154.001930]  blk_done_softirq+0x29/0x40
[  154.002696]  __do_softirq+0x133/0x57f

ext4_dio_read_iter
  ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
  file_accessed(iocb->ki_filp) <== this trigger UAF

Ret can be -EIOCBQUEUED which means we will not wait for io completion in
iomap_dio_rw. So the release for ovl_aio_req will be done when io
completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
in ovl_read_iter will do this). But once io finish soon, we may already
release ovl_aio_req before we call file_access in ext4_dio_read_iter.
This can trigger the upper UAF.

Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.

Fixes: 2406a307ac7d ("ovl: implement async IO routines")
Signed-off-by: yangerkun <yangerkun@huawei.com>
---
 fs/overlayfs/file.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 4ac3cd698c7d..0a0acab3bf2b 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -17,6 +17,7 @@
 
 struct ovl_aio_req {
 	struct kiocb iocb;
+	refcount_t ref;
 	struct kiocb *orig_iocb;
 	struct fd fd;
 };
@@ -252,6 +253,17 @@ static rwf_t ovl_iocb_to_rwf(int ifl)
 	return flags;
 }
 
+static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
+{
+	if (refcount_dec_and_test(&aio_req->ref))
+		kmem_cache_free(ovl_aio_request_cachep, aio_req);
+}
+
+static inline void ovl_aio_get(struct ovl_aio_req *aio_req)
+{
+	refcount_inc(&aio_req->ref);
+}
+
 static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 {
 	struct kiocb *iocb = &aio_req->iocb;
@@ -269,7 +281,7 @@ static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 
 	orig_iocb->ki_pos = iocb->ki_pos;
 	fdput(aio_req->fd);
-	kmem_cache_free(ovl_aio_request_cachep, aio_req);
+	ovl_aio_put(aio_req);
 }
 
 static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
@@ -296,6 +308,7 @@ static struct ovl_aio_req *ovl_get_aio_req(struct kiocb *iocb, struct fd *real,
 	kiocb_clone(&req->iocb, iocb, real->file);
 	req->iocb.ki_flags = ifl;
 	req->iocb.ki_complete = ovl_aio_rw_complete;
+	refcount_set(&req->ref, 1);
 	return req;
 }
 
@@ -325,7 +338,9 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 		if (!aio_req)
 			goto out;
 
+		ovl_aio_get(aio_req);
 		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}
@@ -384,7 +399,9 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 		/* Pacify lockdep, same trick as done in aio_write() */
 		__sb_writers_release(file_inode(real.file)->i_sb,
 				     SB_FREEZE_WRITE);
+		ovl_aio_get(aio_req);
 		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}
-- 
2.31.1

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[yangerkun]

Gently ping...

在 2021/9/30 11:22, yangerkun 写道:
> Our testcase trigger follow UAF:
> 
> [  153.939147] ==================================================================
> [  153.942199] BUG: KASAN: use-after-free in ext4_dio_read_iter+0xcc/0x1a0
> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task fsstress/726
> [  153.948182] Call Trace:
> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.951693]  ? kasan_report.cold+0x81/0x165
> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.953190]  ? __asan_load8+0x74/0x110
> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
> [  153.956916]  ? ovl_read_iter+0x15f/0x270
> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
> [  153.959101]  ? aio_read+0x190/0x2d0
> [  153.959750]  ? aio_write+0x3e0/0x3e0
> [  153.960404]  ? __kasan_check_read+0x1d/0x30
> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
> [  153.961978]  ? __put_user_ns+0x40/0x40
> [  153.962714]  ? kasan_poison+0x40/0x90
> [  153.963384]  ? set_alloc_info+0x46/0x70
> [  153.964102]  ? __kasan_check_write+0x20/0x30
> [  153.964856]  ? __fget_files+0x106/0x180
> [  153.965571]  ? io_submit_one+0xaa7/0x1480
> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
> [  153.967713]  ? ioctl_file_clone+0x110/0x110
> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
> [  153.975575]  ? __kasan_check_read+0x1d/0x30
> [  153.976749]  ? do_syscall_64+0x35/0x80
> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
> [  153.979436]
> [  153.979738] Allocated by task 726:
> [  153.980352]  kasan_save_stack+0x23/0x60
> [  153.981054]  set_alloc_info+0x46/0x70
> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
> [  153.982492]  kmem_cache_alloc+0x153/0x750
> [  153.983953]  ovl_read_iter+0x13b/0x270
> [  153.984689]  aio_read+0x190/0x2d0
> [  153.985332]  io_submit_one+0xaa7/0x1480
> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
> [  153.986878]  do_syscall_64+0x35/0x80
> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [  153.988516]
> [  153.988824] Freed by task 750:
> [  153.989417]  kasan_save_stack+0x23/0x60
> [  153.990140]  kasan_set_track+0x24/0x40
> [  153.990871]  kasan_set_free_info+0x30/0x60
> [  153.991639]  __kasan_slab_free+0x137/0x210
> [  153.992390]  kmem_cache_free+0xf8/0x590
> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
> [  153.996742]  bio_endio+0x40d/0x440
> [  153.997376]  blk_update_request+0x38f/0x820
> [  153.998160]  scsi_end_request+0x56/0x320
> [  153.998872]  scsi_io_completion+0x10a/0xb60
> [  153.999655]  scsi_finish_command+0x194/0x2b0
> [  154.000464]  scsi_complete+0xd7/0x1f0
> [  154.001184]  blk_complete_reqs+0x92/0xb0
> [  154.001930]  blk_done_softirq+0x29/0x40
> [  154.002696]  __do_softirq+0x133/0x57f
> 
> ext4_dio_read_iter
>    ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
>    file_accessed(iocb->ki_filp) <== this trigger UAF
> 
> Ret can be -EIOCBQUEUED which means we will not wait for io completion in
> iomap_dio_rw. So the release for ovl_aio_req will be done when io
> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
> in ovl_read_iter will do this). But once io finish soon, we may already
> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
> This can trigger the upper UAF.
> 
> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
> 
> Fixes: 2406a307ac7d ("ovl: implement async IO routines")
> Signed-off-by: yangerkun <yangerkun@huawei.com>
> ---
>   fs/overlayfs/file.c | 19 ++++++++++++++++++-
>   1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 4ac3cd698c7d..0a0acab3bf2b 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -17,6 +17,7 @@
>   
>   struct ovl_aio_req {
>   	struct kiocb iocb;
> +	refcount_t ref;
>   	struct kiocb *orig_iocb;
>   	struct fd fd;
>   };
> @@ -252,6 +253,17 @@ static rwf_t ovl_iocb_to_rwf(int ifl)
>   	return flags;
>   }
>   
> +static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
> +{
> +	if (refcount_dec_and_test(&aio_req->ref))
> +		kmem_cache_free(ovl_aio_request_cachep, aio_req);
> +}
> +
> +static inline void ovl_aio_get(struct ovl_aio_req *aio_req)
> +{
> +	refcount_inc(&aio_req->ref);
> +}
> +
>   static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
>   {
>   	struct kiocb *iocb = &aio_req->iocb;
> @@ -269,7 +281,7 @@ static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
>   
>   	orig_iocb->ki_pos = iocb->ki_pos;
>   	fdput(aio_req->fd);
> -	kmem_cache_free(ovl_aio_request_cachep, aio_req);
> +	ovl_aio_put(aio_req);
>   }
>   
>   static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
> @@ -296,6 +308,7 @@ static struct ovl_aio_req *ovl_get_aio_req(struct kiocb *iocb, struct fd *real,
>   	kiocb_clone(&req->iocb, iocb, real->file);
>   	req->iocb.ki_flags = ifl;
>   	req->iocb.ki_complete = ovl_aio_rw_complete;
> +	refcount_set(&req->ref, 1);
>   	return req;
>   }
>   
> @@ -325,7 +338,9 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
>   		if (!aio_req)
>   			goto out;
>   
> +		ovl_aio_get(aio_req);
>   		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
> +		ovl_aio_put(aio_req);
>   		if (ret != -EIOCBQUEUED)
>   			ovl_aio_cleanup_handler(aio_req);
>   	}
> @@ -384,7 +399,9 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
>   		/* Pacify lockdep, same trick as done in aio_write() */
>   		__sb_writers_release(file_inode(real.file)->i_sb,
>   				     SB_FREEZE_WRITE);
> +		ovl_aio_get(aio_req);
>   		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
> +		ovl_aio_put(aio_req);
>   		if (ret != -EIOCBQUEUED)
>   			ovl_aio_cleanup_handler(aio_req);
>   	}
> 

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[Miklos Szeredi]

On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
>
> Our testcase trigger follow UAF:
>
> [  153.939147] ==================================================================
> [  153.942199] BUG: KASAN: use-after-free in ext4_dio_read_iter+0xcc/0x1a0
> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task fsstress/726
> [  153.948182] Call Trace:
> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.951693]  ? kasan_report.cold+0x81/0x165
> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.953190]  ? __asan_load8+0x74/0x110
> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
> [  153.956916]  ? ovl_read_iter+0x15f/0x270
> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
> [  153.959101]  ? aio_read+0x190/0x2d0
> [  153.959750]  ? aio_write+0x3e0/0x3e0
> [  153.960404]  ? __kasan_check_read+0x1d/0x30
> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
> [  153.961978]  ? __put_user_ns+0x40/0x40
> [  153.962714]  ? kasan_poison+0x40/0x90
> [  153.963384]  ? set_alloc_info+0x46/0x70
> [  153.964102]  ? __kasan_check_write+0x20/0x30
> [  153.964856]  ? __fget_files+0x106/0x180
> [  153.965571]  ? io_submit_one+0xaa7/0x1480
> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
> [  153.967713]  ? ioctl_file_clone+0x110/0x110
> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
> [  153.975575]  ? __kasan_check_read+0x1d/0x30
> [  153.976749]  ? do_syscall_64+0x35/0x80
> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
> [  153.979436]
> [  153.979738] Allocated by task 726:
> [  153.980352]  kasan_save_stack+0x23/0x60
> [  153.981054]  set_alloc_info+0x46/0x70
> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
> [  153.982492]  kmem_cache_alloc+0x153/0x750
> [  153.983953]  ovl_read_iter+0x13b/0x270
> [  153.984689]  aio_read+0x190/0x2d0
> [  153.985332]  io_submit_one+0xaa7/0x1480
> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
> [  153.986878]  do_syscall_64+0x35/0x80
> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [  153.988516]
> [  153.988824] Freed by task 750:
> [  153.989417]  kasan_save_stack+0x23/0x60
> [  153.990140]  kasan_set_track+0x24/0x40
> [  153.990871]  kasan_set_free_info+0x30/0x60
> [  153.991639]  __kasan_slab_free+0x137/0x210
> [  153.992390]  kmem_cache_free+0xf8/0x590
> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
> [  153.996742]  bio_endio+0x40d/0x440
> [  153.997376]  blk_update_request+0x38f/0x820
> [  153.998160]  scsi_end_request+0x56/0x320
> [  153.998872]  scsi_io_completion+0x10a/0xb60
> [  153.999655]  scsi_finish_command+0x194/0x2b0
> [  154.000464]  scsi_complete+0xd7/0x1f0
> [  154.001184]  blk_complete_reqs+0x92/0xb0
> [  154.001930]  blk_done_softirq+0x29/0x40
> [  154.002696]  __do_softirq+0x133/0x57f
>
> ext4_dio_read_iter
>   ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
>   file_accessed(iocb->ki_filp) <== this trigger UAF
>
> Ret can be -EIOCBQUEUED which means we will not wait for io completion in
> iomap_dio_rw. So the release for ovl_aio_req will be done when io
> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
> in ovl_read_iter will do this). But once io finish soon, we may already
> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
> This can trigger the upper UAF.
>
> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.

Looks good at a glance.   Will review more fully.

Thanks,
MIklos

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[yangerkun]

在 2021/10/8 23:13, Miklos Szeredi 写道:
> On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
>>
>> Our testcase trigger follow UAF:
>>
>> [  153.939147] ==================================================================
>> [  153.942199] BUG: KASAN: use-after-free in ext4_dio_read_iter+0xcc/0x1a0
>> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task fsstress/726
>> [  153.948182] Call Trace:
>> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
>> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
>> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
>> [  153.951693]  ? kasan_report.cold+0x81/0x165
>> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
>> [  153.953190]  ? __asan_load8+0x74/0x110
>> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
>> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
>> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
>> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
>> [  153.956916]  ? ovl_read_iter+0x15f/0x270
>> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
>> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
>> [  153.959101]  ? aio_read+0x190/0x2d0
>> [  153.959750]  ? aio_write+0x3e0/0x3e0
>> [  153.960404]  ? __kasan_check_read+0x1d/0x30
>> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
>> [  153.961978]  ? __put_user_ns+0x40/0x40
>> [  153.962714]  ? kasan_poison+0x40/0x90
>> [  153.963384]  ? set_alloc_info+0x46/0x70
>> [  153.964102]  ? __kasan_check_write+0x20/0x30
>> [  153.964856]  ? __fget_files+0x106/0x180
>> [  153.965571]  ? io_submit_one+0xaa7/0x1480
>> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
>> [  153.967713]  ? ioctl_file_clone+0x110/0x110
>> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
>> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
>> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
>> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
>> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
>> [  153.975575]  ? __kasan_check_read+0x1d/0x30
>> [  153.976749]  ? do_syscall_64+0x35/0x80
>> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
>> [  153.979436]
>> [  153.979738] Allocated by task 726:
>> [  153.980352]  kasan_save_stack+0x23/0x60
>> [  153.981054]  set_alloc_info+0x46/0x70
>> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
>> [  153.982492]  kmem_cache_alloc+0x153/0x750
>> [  153.983953]  ovl_read_iter+0x13b/0x270
>> [  153.984689]  aio_read+0x190/0x2d0
>> [  153.985332]  io_submit_one+0xaa7/0x1480
>> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
>> [  153.986878]  do_syscall_64+0x35/0x80
>> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>> [  153.988516]
>> [  153.988824] Freed by task 750:
>> [  153.989417]  kasan_save_stack+0x23/0x60
>> [  153.990140]  kasan_set_track+0x24/0x40
>> [  153.990871]  kasan_set_free_info+0x30/0x60
>> [  153.991639]  __kasan_slab_free+0x137/0x210
>> [  153.992390]  kmem_cache_free+0xf8/0x590
>> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
>> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
>> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
>> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
>> [  153.996742]  bio_endio+0x40d/0x440
>> [  153.997376]  blk_update_request+0x38f/0x820
>> [  153.998160]  scsi_end_request+0x56/0x320
>> [  153.998872]  scsi_io_completion+0x10a/0xb60
>> [  153.999655]  scsi_finish_command+0x194/0x2b0
>> [  154.000464]  scsi_complete+0xd7/0x1f0
>> [  154.001184]  blk_complete_reqs+0x92/0xb0
>> [  154.001930]  blk_done_softirq+0x29/0x40
>> [  154.002696]  __do_softirq+0x133/0x57f
>>
>> ext4_dio_read_iter
>>    ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
>>    file_accessed(iocb->ki_filp) <== this trigger UAF
>>
>> Ret can be -EIOCBQUEUED which means we will not wait for io completion in
>> iomap_dio_rw. So the release for ovl_aio_req will be done when io
>> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
>> in ovl_read_iter will do this). But once io finish soon, we may already
>> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
>> This can trigger the upper UAF.
>>
>> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
> 
> Looks good at a glance.   Will review more fully.

Hi,

Any comments for this patch? :)

> 
> Thanks,
> MIklos
> .
> 

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[yangerkun]

在 2021/10/18 22:26, yangerkun 写道:
> 
> 
> 在 2021/10/8 23:13, Miklos Szeredi 写道:
>> On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
>>>
>>> Our testcase trigger follow UAF:
>>>
>>> [  153.939147] 
>>> ==================================================================
>>> [  153.942199] BUG: KASAN: use-after-free in 
>>> ext4_dio_read_iter+0xcc/0x1a0
>>> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task 
>>> fsstress/726
>>> [  153.948182] Call Trace:
>>> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
>>> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
>>> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
>>> [  153.951693]  ? kasan_report.cold+0x81/0x165
>>> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
>>> [  153.953190]  ? __asan_load8+0x74/0x110
>>> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
>>> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
>>> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
>>> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
>>> [  153.956916]  ? ovl_read_iter+0x15f/0x270
>>> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
>>> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
>>> [  153.959101]  ? aio_read+0x190/0x2d0
>>> [  153.959750]  ? aio_write+0x3e0/0x3e0
>>> [  153.960404]  ? __kasan_check_read+0x1d/0x30
>>> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
>>> [  153.961978]  ? __put_user_ns+0x40/0x40
>>> [  153.962714]  ? kasan_poison+0x40/0x90
>>> [  153.963384]  ? set_alloc_info+0x46/0x70
>>> [  153.964102]  ? __kasan_check_write+0x20/0x30
>>> [  153.964856]  ? __fget_files+0x106/0x180
>>> [  153.965571]  ? io_submit_one+0xaa7/0x1480
>>> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
>>> [  153.967713]  ? ioctl_file_clone+0x110/0x110
>>> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
>>> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
>>> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
>>> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
>>> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
>>> [  153.975575]  ? __kasan_check_read+0x1d/0x30
>>> [  153.976749]  ? do_syscall_64+0x35/0x80
>>> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
>>> [  153.979436]
>>> [  153.979738] Allocated by task 726:
>>> [  153.980352]  kasan_save_stack+0x23/0x60
>>> [  153.981054]  set_alloc_info+0x46/0x70
>>> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
>>> [  153.982492]  kmem_cache_alloc+0x153/0x750
>>> [  153.983953]  ovl_read_iter+0x13b/0x270
>>> [  153.984689]  aio_read+0x190/0x2d0
>>> [  153.985332]  io_submit_one+0xaa7/0x1480
>>> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
>>> [  153.986878]  do_syscall_64+0x35/0x80
>>> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>>> [  153.988516]
>>> [  153.988824] Freed by task 750:
>>> [  153.989417]  kasan_save_stack+0x23/0x60
>>> [  153.990140]  kasan_set_track+0x24/0x40
>>> [  153.990871]  kasan_set_free_info+0x30/0x60
>>> [  153.991639]  __kasan_slab_free+0x137/0x210
>>> [  153.992390]  kmem_cache_free+0xf8/0x590
>>> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
>>> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
>>> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
>>> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
>>> [  153.996742]  bio_endio+0x40d/0x440
>>> [  153.997376]  blk_update_request+0x38f/0x820
>>> [  153.998160]  scsi_end_request+0x56/0x320
>>> [  153.998872]  scsi_io_completion+0x10a/0xb60
>>> [  153.999655]  scsi_finish_command+0x194/0x2b0
>>> [  154.000464]  scsi_complete+0xd7/0x1f0
>>> [  154.001184]  blk_complete_reqs+0x92/0xb0
>>> [  154.001930]  blk_done_softirq+0x29/0x40
>>> [  154.002696]  __do_softirq+0x133/0x57f
>>>
>>> ext4_dio_read_iter
>>>    ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
>>>    file_accessed(iocb->ki_filp) <== this trigger UAF
>>>
>>> Ret can be -EIOCBQUEUED which means we will not wait for io 
>>> completion in
>>> iomap_dio_rw. So the release for ovl_aio_req will be done when io
>>> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
>>> in ovl_read_iter will do this). But once io finish soon, we may already
>>> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
>>> This can trigger the upper UAF.
>>>
>>> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
>>
>> Looks good at a glance.   Will review more fully.
> 
> Hi,
> 
> Any comments for this patch? :)

Ping...

> 
>>
>> Thanks,
>> MIklos
>> .
>>
> .

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[Miklos Szeredi]

On Thu, 28 Oct 2021 at 14:41, yangerkun <yangerkun@huawei.com> wrote:
>
>
>
> 在 2021/10/18 22:26, yangerkun 写道:
> >
> >
> > 在 2021/10/8 23:13, Miklos Szeredi 写道:
> >> On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
> >>>
> >>> Our testcase trigger follow UAF:
> >>>
> >>> [  153.939147]
> >>> ==================================================================
> >>> [  153.942199] BUG: KASAN: use-after-free in
> >>> ext4_dio_read_iter+0xcc/0x1a0
> >>> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task
> >>> fsstress/726
> >>> [  153.948182] Call Trace:
> >>> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
> >>> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>> [  153.951693]  ? kasan_report.cold+0x81/0x165
> >>> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>> [  153.953190]  ? __asan_load8+0x74/0x110
> >>> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
> >>> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
> >>> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
> >>> [  153.956916]  ? ovl_read_iter+0x15f/0x270
> >>> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
> >>> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
> >>> [  153.959101]  ? aio_read+0x190/0x2d0
> >>> [  153.959750]  ? aio_write+0x3e0/0x3e0
> >>> [  153.960404]  ? __kasan_check_read+0x1d/0x30
> >>> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
> >>> [  153.961978]  ? __put_user_ns+0x40/0x40
> >>> [  153.962714]  ? kasan_poison+0x40/0x90
> >>> [  153.963384]  ? set_alloc_info+0x46/0x70
> >>> [  153.964102]  ? __kasan_check_write+0x20/0x30
> >>> [  153.964856]  ? __fget_files+0x106/0x180
> >>> [  153.965571]  ? io_submit_one+0xaa7/0x1480
> >>> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
> >>> [  153.967713]  ? ioctl_file_clone+0x110/0x110
> >>> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
> >>> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
> >>> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
> >>> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
> >>> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
> >>> [  153.975575]  ? __kasan_check_read+0x1d/0x30
> >>> [  153.976749]  ? do_syscall_64+0x35/0x80
> >>> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
> >>> [  153.979436]
> >>> [  153.979738] Allocated by task 726:
> >>> [  153.980352]  kasan_save_stack+0x23/0x60
> >>> [  153.981054]  set_alloc_info+0x46/0x70
> >>> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
> >>> [  153.982492]  kmem_cache_alloc+0x153/0x750
> >>> [  153.983953]  ovl_read_iter+0x13b/0x270
> >>> [  153.984689]  aio_read+0x190/0x2d0
> >>> [  153.985332]  io_submit_one+0xaa7/0x1480
> >>> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
> >>> [  153.986878]  do_syscall_64+0x35/0x80
> >>> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> >>> [  153.988516]
> >>> [  153.988824] Freed by task 750:
> >>> [  153.989417]  kasan_save_stack+0x23/0x60
> >>> [  153.990140]  kasan_set_track+0x24/0x40
> >>> [  153.990871]  kasan_set_free_info+0x30/0x60
> >>> [  153.991639]  __kasan_slab_free+0x137/0x210
> >>> [  153.992390]  kmem_cache_free+0xf8/0x590
> >>> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
> >>> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
> >>> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
> >>> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
> >>> [  153.996742]  bio_endio+0x40d/0x440
> >>> [  153.997376]  blk_update_request+0x38f/0x820
> >>> [  153.998160]  scsi_end_request+0x56/0x320
> >>> [  153.998872]  scsi_io_completion+0x10a/0xb60
> >>> [  153.999655]  scsi_finish_command+0x194/0x2b0
> >>> [  154.000464]  scsi_complete+0xd7/0x1f0
> >>> [  154.001184]  blk_complete_reqs+0x92/0xb0
> >>> [  154.001930]  blk_done_softirq+0x29/0x40
> >>> [  154.002696]  __do_softirq+0x133/0x57f
> >>>
> >>> ext4_dio_read_iter
> >>>    ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
> >>>    file_accessed(iocb->ki_filp) <== this trigger UAF
> >>>
> >>> Ret can be -EIOCBQUEUED which means we will not wait for io
> >>> completion in
> >>> iomap_dio_rw. So the release for ovl_aio_req will be done when io
> >>> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
> >>> in ovl_read_iter will do this). But once io finish soon, we may already
> >>> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
> >>> This can trigger the upper UAF.
> >>>
> >>> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
> >>
> >> Looks good at a glance.   Will review more fully.
> >
> > Hi,
> >
> > Any comments for this patch? :)
>
> Ping...

Now looking...

Thanks,
Miklos

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[Miklos Szeredi]

On Thu, Oct 28, 2021 at 08:41:28PM +0800, yangerkun wrote:
> 
> 
> 在 2021/10/18 22:26, yangerkun 写道:
> > 
> > 
> > 在 2021/10/8 23:13, Miklos Szeredi 写道:
> > > On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
> > > > 
> > > > Our testcase trigger follow UAF:
> > > > 
> > > > [  153.939147]
> > > > ==================================================================
> > > > [  153.942199] BUG: KASAN: use-after-free in
> > > > ext4_dio_read_iter+0xcc/0x1a0
> > > > [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task
> > > > fsstress/726
> > > > [  153.948182] Call Trace:
> > > > [  153.948628]  ? dump_stack_lvl+0x73/0x9f
> > > > [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
> > > > [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
> > > > [  153.951693]  ? kasan_report.cold+0x81/0x165
> > > > [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
> > > > [  153.953190]  ? __asan_load8+0x74/0x110
> > > > [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
> > > > [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
> > > > [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
> > > > [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
> > > > [  153.956916]  ? ovl_read_iter+0x15f/0x270
> > > > [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
> > > > [  153.958436]  ? aio_setup_rw+0xbf/0xe0
> > > > [  153.959101]  ? aio_read+0x190/0x2d0
> > > > [  153.959750]  ? aio_write+0x3e0/0x3e0
> > > > [  153.960404]  ? __kasan_check_read+0x1d/0x30
> > > > [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
> > > > [  153.961978]  ? __put_user_ns+0x40/0x40
> > > > [  153.962714]  ? kasan_poison+0x40/0x90
> > > > [  153.963384]  ? set_alloc_info+0x46/0x70
> > > > [  153.964102]  ? __kasan_check_write+0x20/0x30
> > > > [  153.964856]  ? __fget_files+0x106/0x180
> > > > [  153.965571]  ? io_submit_one+0xaa7/0x1480
> > > > [  153.966325]  ? aio_poll_complete_work+0x590/0x590
> > > > [  153.967713]  ? ioctl_file_clone+0x110/0x110
> > > > [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
> > > > [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
> > > > [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
> > > > [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
> > > > [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
> > > > [  153.975575]  ? __kasan_check_read+0x1d/0x30
> > > > [  153.976749]  ? do_syscall_64+0x35/0x80
> > > > [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > > [  153.979436]
> > > > [  153.979738] Allocated by task 726:
> > > > [  153.980352]  kasan_save_stack+0x23/0x60
> > > > [  153.981054]  set_alloc_info+0x46/0x70
> > > > [  153.981745]  __kasan_slab_alloc+0x4c/0x90
> > > > [  153.982492]  kmem_cache_alloc+0x153/0x750
> > > > [  153.983953]  ovl_read_iter+0x13b/0x270
> > > > [  153.984689]  aio_read+0x190/0x2d0
> > > > [  153.985332]  io_submit_one+0xaa7/0x1480
> > > > [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
> > > > [  153.986878]  do_syscall_64+0x35/0x80
> > > > [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > > [  153.988516]
> > > > [  153.988824] Freed by task 750:
> > > > [  153.989417]  kasan_save_stack+0x23/0x60
> > > > [  153.990140]  kasan_set_track+0x24/0x40
> > > > [  153.990871]  kasan_set_free_info+0x30/0x60
> > > > [  153.991639]  __kasan_slab_free+0x137/0x210
> > > > [  153.992390]  kmem_cache_free+0xf8/0x590
> > > > [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
> > > > [  153.994205]  ovl_aio_rw_complete+0x31/0x60
> > > > [  153.995043]  iomap_dio_complete_work+0x4b/0x60
> > > > [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
> > > > [  153.996742]  bio_endio+0x40d/0x440
> > > > [  153.997376]  blk_update_request+0x38f/0x820
> > > > [  153.998160]  scsi_end_request+0x56/0x320
> > > > [  153.998872]  scsi_io_completion+0x10a/0xb60
> > > > [  153.999655]  scsi_finish_command+0x194/0x2b0
> > > > [  154.000464]  scsi_complete+0xd7/0x1f0
> > > > [  154.001184]  blk_complete_reqs+0x92/0xb0
> > > > [  154.001930]  blk_done_softirq+0x29/0x40
> > > > [  154.002696]  __do_softirq+0x133/0x57f
> > > > 
> > > > ext4_dio_read_iter
> > > >    ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
> > > >    file_accessed(iocb->ki_filp) <== this trigger UAF
> > > > 
> > > > Ret can be -EIOCBQUEUED which means we will not wait for io
> > > > completion in
> > > > iomap_dio_rw. So the release for ovl_aio_req will be done when io
> > > > completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
> > > > in ovl_read_iter will do this). But once io finish soon, we may already
> > > > release ovl_aio_req before we call file_access in ext4_dio_read_iter.
> > > > This can trigger the upper UAF.
> > > > 
> > > > Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
> > > 
> > > Looks good at a glance.   Will review more fully.
> > 
> > Hi,
> > 
> > Any comments for this patch? :)

Thanks for the patch.  I found one issue: the fdput() needs to be moved to the
destruction as well, since the iocb->ki_filp reference comes from aio_req->fd.

Other than that, it looks good.

Minor things:

- instead of setting refcount to 1 and incrementing it, just initialize it to 2

- code deduplication can come after the fix (if at all), this helps backporting

- cleaned up header comment

Here's the updated patch, can you please verify that I didn't break anything?

Thanks,
Miklos
---

From: yangerkun <yangerkun@huawei.com>
Subject: ovl: fix use after free in struct ovl_aio_req
Date: Thu, 30 Sep 2021 11:22:28 +0800

Example for triggering use after free in a overlay on ext4 setup:

aio_read
  ovl_read_iter
    vfs_iter_read
      ext4_file_read_iter
        ext4_dio_read_iter
          iomap_dio_rw -> -EIOCBQUEUED
          /*
	   * Here IO is completed in a separate thread,
	   * ovl_aio_cleanup_handler() frees aio_req which has iocb embedded
	   */
          file_accessed(iocb->ki_filp); /**BOOM**/

Fix by introducing a refcount in ovl_aio_req similarly to aio_kiocb.  This
guarantees that iocb is only freed after vfs_read/write_iter() returns on
underlying fs.

Fixes: 2406a307ac7d ("ovl: implement async IO routines")
Signed-off-by: yangerkun <yangerkun@huawei.com>
Link: https://lore.kernel.org/r/20210930032228.3199690-3-yangerkun@huawei.com/
Cc: <stable@vger.kernel.org> # v5.6
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/overlayfs/file.c |   16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -17,6 +17,7 @@
 
 struct ovl_aio_req {
 	struct kiocb iocb;
+	refcount_t ref;
 	struct kiocb *orig_iocb;
 	struct fd fd;
 };
@@ -252,6 +253,14 @@ static rwf_t ovl_iocb_to_rwf(int ifl)
 	return flags;
 }
 
+static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
+{
+	if (refcount_dec_and_test(&aio_req->ref)) {
+		fdput(aio_req->fd);
+		kmem_cache_free(ovl_aio_request_cachep, aio_req);
+	}
+}
+
 static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 {
 	struct kiocb *iocb = &aio_req->iocb;
@@ -268,8 +277,7 @@ static void ovl_aio_cleanup_handler(stru
 	}
 
 	orig_iocb->ki_pos = iocb->ki_pos;
-	fdput(aio_req->fd);
-	kmem_cache_free(ovl_aio_request_cachep, aio_req);
+	ovl_aio_put(aio_req);
 }
 
 static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
@@ -319,7 +327,9 @@ static ssize_t ovl_read_iter(struct kioc
 		aio_req->orig_iocb = iocb;
 		kiocb_clone(&aio_req->iocb, iocb, real.file);
 		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+		refcount_set(&aio_req->ref, 2);
 		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}
@@ -390,7 +400,9 @@ static ssize_t ovl_write_iter(struct kio
 		kiocb_clone(&aio_req->iocb, iocb, real.file);
 		aio_req->iocb.ki_flags = ifl;
 		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+		refcount_set(&aio_req->ref, 2);
 		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[yangerkun]

On 2021/10/29 19:40, Miklos Szeredi wrote:
> On Thu, Oct 28, 2021 at 08:41:28PM +0800, yangerkun wrote:
>>
>>
>> 在 2021/10/18 22:26, yangerkun 写道:
>>>
>>>
>>> 在 2021/10/8 23:13, Miklos Szeredi 写道:
>>>> On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
>>>>>
>>>>> Our testcase trigger follow UAF:
>>>>>
>>>>> [  153.939147]
>>>>> ==================================================================
>>>>> [  153.942199] BUG: KASAN: use-after-free in
>>>>> ext4_dio_read_iter+0xcc/0x1a0
>>>>> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task
>>>>> fsstress/726
>>>>> [  153.948182] Call Trace:
>>>>> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
>>>>> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>> [  153.951693]  ? kasan_report.cold+0x81/0x165
>>>>> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>> [  153.953190]  ? __asan_load8+0x74/0x110
>>>>> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
>>>>> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
>>>>> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
>>>>> [  153.956916]  ? ovl_read_iter+0x15f/0x270
>>>>> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
>>>>> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
>>>>> [  153.959101]  ? aio_read+0x190/0x2d0
>>>>> [  153.959750]  ? aio_write+0x3e0/0x3e0
>>>>> [  153.960404]  ? __kasan_check_read+0x1d/0x30
>>>>> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
>>>>> [  153.961978]  ? __put_user_ns+0x40/0x40
>>>>> [  153.962714]  ? kasan_poison+0x40/0x90
>>>>> [  153.963384]  ? set_alloc_info+0x46/0x70
>>>>> [  153.964102]  ? __kasan_check_write+0x20/0x30
>>>>> [  153.964856]  ? __fget_files+0x106/0x180
>>>>> [  153.965571]  ? io_submit_one+0xaa7/0x1480
>>>>> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
>>>>> [  153.967713]  ? ioctl_file_clone+0x110/0x110
>>>>> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
>>>>> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
>>>>> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
>>>>> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
>>>>> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
>>>>> [  153.975575]  ? __kasan_check_read+0x1d/0x30
>>>>> [  153.976749]  ? do_syscall_64+0x35/0x80
>>>>> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
>>>>> [  153.979436]
>>>>> [  153.979738] Allocated by task 726:
>>>>> [  153.980352]  kasan_save_stack+0x23/0x60
>>>>> [  153.981054]  set_alloc_info+0x46/0x70
>>>>> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
>>>>> [  153.982492]  kmem_cache_alloc+0x153/0x750
>>>>> [  153.983953]  ovl_read_iter+0x13b/0x270
>>>>> [  153.984689]  aio_read+0x190/0x2d0
>>>>> [  153.985332]  io_submit_one+0xaa7/0x1480
>>>>> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
>>>>> [  153.986878]  do_syscall_64+0x35/0x80
>>>>> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>>>>> [  153.988516]
>>>>> [  153.988824] Freed by task 750:
>>>>> [  153.989417]  kasan_save_stack+0x23/0x60
>>>>> [  153.990140]  kasan_set_track+0x24/0x40
>>>>> [  153.990871]  kasan_set_free_info+0x30/0x60
>>>>> [  153.991639]  __kasan_slab_free+0x137/0x210
>>>>> [  153.992390]  kmem_cache_free+0xf8/0x590
>>>>> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
>>>>> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
>>>>> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
>>>>> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
>>>>> [  153.996742]  bio_endio+0x40d/0x440
>>>>> [  153.997376]  blk_update_request+0x38f/0x820
>>>>> [  153.998160]  scsi_end_request+0x56/0x320
>>>>> [  153.998872]  scsi_io_completion+0x10a/0xb60
>>>>> [  153.999655]  scsi_finish_command+0x194/0x2b0
>>>>> [  154.000464]  scsi_complete+0xd7/0x1f0
>>>>> [  154.001184]  blk_complete_reqs+0x92/0xb0
>>>>> [  154.001930]  blk_done_softirq+0x29/0x40
>>>>> [  154.002696]  __do_softirq+0x133/0x57f
>>>>>
>>>>> ext4_dio_read_iter
>>>>>     ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
>>>>>     file_accessed(iocb->ki_filp) <== this trigger UAF
>>>>>
>>>>> Ret can be -EIOCBQUEUED which means we will not wait for io
>>>>> completion in
>>>>> iomap_dio_rw. So the release for ovl_aio_req will be done when io
>>>>> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
>>>>> in ovl_read_iter will do this). But once io finish soon, we may already
>>>>> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
>>>>> This can trigger the upper UAF.
>>>>>
>>>>> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
>>>>
>>>> Looks good at a glance.   Will review more fully.
>>>
>>> Hi,
>>>
>>> Any comments for this patch? :)
> 
> Thanks for the patch.  I found one issue: the fdput() needs to be moved to the
> destruction as well, since the iocb->ki_filp reference comes from aio_req->fd.

Hi, it seems we will only use aio_req->iocb in ovl_aio_cleanup_handler 
before we call fdput(aio_req->fd):

static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
{
         struct kiocb *iocb = &aio_req->iocb;
         struct kiocb *orig_iocb = aio_req->orig_iocb;

         if (iocb->ki_flags & IOCB_WRITE) {
                 struct inode *inode = file_inode(orig_iocb->ki_filp);

                 /* Actually acquired in ovl_write_iter() */
                 __sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb,
                                       SB_FREEZE_WRITE);
                 file_end_write(iocb->ki_filp);
                 <=== use iocb
                 ovl_copyattr(ovl_inode_real(inode), inode);
         }

         orig_iocb->ki_pos = iocb->ki_pos;
         fdput(aio_req->fd); <=== release aio_req->fd
         kmem_cache_free(ovl_aio_request_cachep, aio_req);
}

So call fdput(aio_req->fd) in ovl_aio_cleanup_handler or ovl_aio_put
seems all ok for me.

> 
> Other than that, it looks good.
> 
> Minor things:
> 
> - instead of setting refcount to 1 and incrementing it, just initialize it to 2
> 
> - code deduplication can come after the fix (if at all), this helps backporting

Agree.

> 
> - cleaned up header comment
> 
> Here's the updated patch, can you please verify that I didn't break anything?

Thanks! This patch can help pass the test!

> 
> Thanks,
> Miklos
> ---
> 
> From: yangerkun <yangerkun@huawei.com>
> Subject: ovl: fix use after free in struct ovl_aio_req
> Date: Thu, 30 Sep 2021 11:22:28 +0800
> 
> Example for triggering use after free in a overlay on ext4 setup:
> 
> aio_read
>    ovl_read_iter
>      vfs_iter_read
>        ext4_file_read_iter
>          ext4_dio_read_iter
>            iomap_dio_rw -> -EIOCBQUEUED
>            /*
> 	   * Here IO is completed in a separate thread,
> 	   * ovl_aio_cleanup_handler() frees aio_req which has iocb embedded
> 	   */
>            file_accessed(iocb->ki_filp); /**BOOM**/
> 
> Fix by introducing a refcount in ovl_aio_req similarly to aio_kiocb.  This
> guarantees that iocb is only freed after vfs_read/write_iter() returns on
> underlying fs.
> 
> Fixes: 2406a307ac7d ("ovl: implement async IO routines")
> Signed-off-by: yangerkun <yangerkun@huawei.com>
> Link: https://lore.kernel.org/r/20210930032228.3199690-3-yangerkun@huawei.com/
> Cc: <stable@vger.kernel.org> # v5.6
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> ---
>   fs/overlayfs/file.c |   16 ++++++++++++++--
>   1 file changed, 14 insertions(+), 2 deletions(-)
> 
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -17,6 +17,7 @@
>   
>   struct ovl_aio_req {
>   	struct kiocb iocb;
> +	refcount_t ref;
>   	struct kiocb *orig_iocb;
>   	struct fd fd;
>   };
> @@ -252,6 +253,14 @@ static rwf_t ovl_iocb_to_rwf(int ifl)
>   	return flags;
>   }
>   
> +static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
> +{
> +	if (refcount_dec_and_test(&aio_req->ref)) {
> +		fdput(aio_req->fd);
> +		kmem_cache_free(ovl_aio_request_cachep, aio_req);
> +	}
> +}
> +
>   static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
>   {
>   	struct kiocb *iocb = &aio_req->iocb;
> @@ -268,8 +277,7 @@ static void ovl_aio_cleanup_handler(stru
>   	}
>   
>   	orig_iocb->ki_pos = iocb->ki_pos;
> -	fdput(aio_req->fd);
> -	kmem_cache_free(ovl_aio_request_cachep, aio_req);
> +	ovl_aio_put(aio_req);
>   }
>   
>   static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
> @@ -319,7 +327,9 @@ static ssize_t ovl_read_iter(struct kioc
>   		aio_req->orig_iocb = iocb;
>   		kiocb_clone(&aio_req->iocb, iocb, real.file);
>   		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
> +		refcount_set(&aio_req->ref, 2);
>   		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
> +		ovl_aio_put(aio_req);
>   		if (ret != -EIOCBQUEUED)
>   			ovl_aio_cleanup_handler(aio_req);
>   	}
> @@ -390,7 +400,9 @@ static ssize_t ovl_write_iter(struct kio
>   		kiocb_clone(&aio_req->iocb, iocb, real.file);
>   		aio_req->iocb.ki_flags = ifl;
>   		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
> +		refcount_set(&aio_req->ref, 2);
>   		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
> +		ovl_aio_put(aio_req);
>   		if (ret != -EIOCBQUEUED)
>   			ovl_aio_cleanup_handler(aio_req);
>   	}
> .
> 

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[Miklos Szeredi]

On Mon, 1 Nov 2021 at 05:02, yangerkun <yangerkun@huawei.com> wrote:
>
>
>
> On 2021/10/29 19:40, Miklos Szeredi wrote:
> > On Thu, Oct 28, 2021 at 08:41:28PM +0800, yangerkun wrote:
> >>
> >>
> >> 在 2021/10/18 22:26, yangerkun 写道:
> >>>
> >>>
> >>> 在 2021/10/8 23:13, Miklos Szeredi 写道:
> >>>> On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
> >>>>>
> >>>>> Our testcase trigger follow UAF:
> >>>>>
> >>>>> [  153.939147]
> >>>>> ==================================================================
> >>>>> [  153.942199] BUG: KASAN: use-after-free in
> >>>>> ext4_dio_read_iter+0xcc/0x1a0
> >>>>> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task
> >>>>> fsstress/726
> >>>>> [  153.948182] Call Trace:
> >>>>> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
> >>>>> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>>>> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>>>> [  153.951693]  ? kasan_report.cold+0x81/0x165
> >>>>> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>>>> [  153.953190]  ? __asan_load8+0x74/0x110
> >>>>> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
> >>>>> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
> >>>>> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
> >>>>> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
> >>>>> [  153.956916]  ? ovl_read_iter+0x15f/0x270
> >>>>> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
> >>>>> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
> >>>>> [  153.959101]  ? aio_read+0x190/0x2d0
> >>>>> [  153.959750]  ? aio_write+0x3e0/0x3e0
> >>>>> [  153.960404]  ? __kasan_check_read+0x1d/0x30
> >>>>> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
> >>>>> [  153.961978]  ? __put_user_ns+0x40/0x40
> >>>>> [  153.962714]  ? kasan_poison+0x40/0x90
> >>>>> [  153.963384]  ? set_alloc_info+0x46/0x70
> >>>>> [  153.964102]  ? __kasan_check_write+0x20/0x30
> >>>>> [  153.964856]  ? __fget_files+0x106/0x180
> >>>>> [  153.965571]  ? io_submit_one+0xaa7/0x1480
> >>>>> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
> >>>>> [  153.967713]  ? ioctl_file_clone+0x110/0x110
> >>>>> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
> >>>>> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
> >>>>> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
> >>>>> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
> >>>>> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
> >>>>> [  153.975575]  ? __kasan_check_read+0x1d/0x30
> >>>>> [  153.976749]  ? do_syscall_64+0x35/0x80
> >>>>> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
> >>>>> [  153.979436]
> >>>>> [  153.979738] Allocated by task 726:
> >>>>> [  153.980352]  kasan_save_stack+0x23/0x60
> >>>>> [  153.981054]  set_alloc_info+0x46/0x70
> >>>>> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
> >>>>> [  153.982492]  kmem_cache_alloc+0x153/0x750
> >>>>> [  153.983953]  ovl_read_iter+0x13b/0x270
> >>>>> [  153.984689]  aio_read+0x190/0x2d0
> >>>>> [  153.985332]  io_submit_one+0xaa7/0x1480
> >>>>> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
> >>>>> [  153.986878]  do_syscall_64+0x35/0x80
> >>>>> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> >>>>> [  153.988516]
> >>>>> [  153.988824] Freed by task 750:
> >>>>> [  153.989417]  kasan_save_stack+0x23/0x60
> >>>>> [  153.990140]  kasan_set_track+0x24/0x40
> >>>>> [  153.990871]  kasan_set_free_info+0x30/0x60
> >>>>> [  153.991639]  __kasan_slab_free+0x137/0x210
> >>>>> [  153.992390]  kmem_cache_free+0xf8/0x590
> >>>>> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
> >>>>> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
> >>>>> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
> >>>>> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
> >>>>> [  153.996742]  bio_endio+0x40d/0x440
> >>>>> [  153.997376]  blk_update_request+0x38f/0x820
> >>>>> [  153.998160]  scsi_end_request+0x56/0x320
> >>>>> [  153.998872]  scsi_io_completion+0x10a/0xb60
> >>>>> [  153.999655]  scsi_finish_command+0x194/0x2b0
> >>>>> [  154.000464]  scsi_complete+0xd7/0x1f0
> >>>>> [  154.001184]  blk_complete_reqs+0x92/0xb0
> >>>>> [  154.001930]  blk_done_softirq+0x29/0x40
> >>>>> [  154.002696]  __do_softirq+0x133/0x57f
> >>>>>
> >>>>> ext4_dio_read_iter
> >>>>>     ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
> >>>>>     file_accessed(iocb->ki_filp) <== this trigger UAF
> >>>>>
> >>>>> Ret can be -EIOCBQUEUED which means we will not wait for io
> >>>>> completion in
> >>>>> iomap_dio_rw. So the release for ovl_aio_req will be done when io
> >>>>> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
> >>>>> in ovl_read_iter will do this). But once io finish soon, we may already
> >>>>> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
> >>>>> This can trigger the upper UAF.
> >>>>>
> >>>>> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
> >>>>
> >>>> Looks good at a glance.   Will review more fully.
> >>>
> >>> Hi,
> >>>
> >>> Any comments for this patch? :)
> >
> > Thanks for the patch.  I found one issue: the fdput() needs to be moved to the
> > destruction as well, since the iocb->ki_filp reference comes from aio_req->fd.
>
> Hi, it seems we will only use aio_req->iocb in ovl_aio_cleanup_handler
> before we call fdput(aio_req->fd):

Correct.  However I'm taking about this call:
file_accessed(iocb->ki_filp).  If the fdput() is done from
ovl_aio_cleanup_handler() which is called from ->ki_complete() then
this would put the file, agains resulting in a UAF, only inside
file_accessed() this time.   The reason why you weren't seeing this,
is probably that most of the time aio_req->fd is from
file->private_data, which is the real file obtained at open time, and
which isn't actually closed at fdput() (flags == 0).

>
> static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
> {
>          struct kiocb *iocb = &aio_req->iocb;
>          struct kiocb *orig_iocb = aio_req->orig_iocb;
>
>          if (iocb->ki_flags & IOCB_WRITE) {
>                  struct inode *inode = file_inode(orig_iocb->ki_filp);
>
>                  /* Actually acquired in ovl_write_iter() */
>                  __sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb,
>                                        SB_FREEZE_WRITE);
>                  file_end_write(iocb->ki_filp);
>                  <=== use iocb
>                  ovl_copyattr(ovl_inode_real(inode), inode);
>          }
>
>          orig_iocb->ki_pos = iocb->ki_pos;
>          fdput(aio_req->fd); <=== release aio_req->fd
>          kmem_cache_free(ovl_aio_request_cachep, aio_req);
> }
>
> So call fdput(aio_req->fd) in ovl_aio_cleanup_handler or ovl_aio_put
> seems all ok for me.
>
> >
> > Other than that, it looks good.
> >
> > Minor things:
> >
> > - instead of setting refcount to 1 and incrementing it, just initialize it to 2
> >
> > - code deduplication can come after the fix (if at all), this helps backporting
>
> Agree.
>
> >
> > - cleaned up header comment
> >
> > Here's the updated patch, can you please verify that I didn't break anything?
>
> Thanks! This patch can help pass the test!

Great, thanks.

Miklos

Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req

[yangerkun]

On 2021/11/1 17:15, Miklos Szeredi wrote:
> On Mon, 1 Nov 2021 at 05:02, yangerkun <yangerkun@huawei.com> wrote:
>>
>>
>>
>> On 2021/10/29 19:40, Miklos Szeredi wrote:
>>> On Thu, Oct 28, 2021 at 08:41:28PM +0800, yangerkun wrote:
>>>>
>>>>
>>>> 在 2021/10/18 22:26, yangerkun 写道:
>>>>>
>>>>>
>>>>> 在 2021/10/8 23:13, Miklos Szeredi 写道:
>>>>>> On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@huawei.com> wrote:
>>>>>>>
>>>>>>> Our testcase trigger follow UAF:
>>>>>>>
>>>>>>> [  153.939147]
>>>>>>> ==================================================================
>>>>>>> [  153.942199] BUG: KASAN: use-after-free in
>>>>>>> ext4_dio_read_iter+0xcc/0x1a0
>>>>>>> [  153.943331] Read of size 8 at addr ffff88803b7f1500 by task
>>>>>>> fsstress/726
>>>>>>> [  153.948182] Call Trace:
>>>>>>> [  153.948628]  ? dump_stack_lvl+0x73/0x9f
>>>>>>> [  153.950255]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>>>> [  153.950972]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>>>> [  153.951693]  ? kasan_report.cold+0x81/0x165
>>>>>>> [  153.952429]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>>>> [  153.953190]  ? __asan_load8+0x74/0x110
>>>>>>> [  153.953856]  ? ext4_dio_read_iter+0xcc/0x1a0
>>>>>>> [  153.954612]  ? ext4_file_read_iter+0x1df/0x2a0
>>>>>>> [  153.955394]  ? ext4_dio_read_iter+0x1a0/0x1a0
>>>>>>> [  153.956159]  ? vfs_iocb_iter_read+0xd5/0x330
>>>>>>> [  153.956916]  ? ovl_read_iter+0x15f/0x270
>>>>>>> [  153.957605]  ? ovl_aio_cleanup_handler+0x2a0/0x2a0
>>>>>>> [  153.958436]  ? aio_setup_rw+0xbf/0xe0
>>>>>>> [  153.959101]  ? aio_read+0x190/0x2d0
>>>>>>> [  153.959750]  ? aio_write+0x3e0/0x3e0
>>>>>>> [  153.960404]  ? __kasan_check_read+0x1d/0x30
>>>>>>> [  153.961167]  ? ext4_file_getattr+0x116/0x1b0
>>>>>>> [  153.961978]  ? __put_user_ns+0x40/0x40
>>>>>>> [  153.962714]  ? kasan_poison+0x40/0x90
>>>>>>> [  153.963384]  ? set_alloc_info+0x46/0x70
>>>>>>> [  153.964102]  ? __kasan_check_write+0x20/0x30
>>>>>>> [  153.964856]  ? __fget_files+0x106/0x180
>>>>>>> [  153.965571]  ? io_submit_one+0xaa7/0x1480
>>>>>>> [  153.966325]  ? aio_poll_complete_work+0x590/0x590
>>>>>>> [  153.967713]  ? ioctl_file_clone+0x110/0x110
>>>>>>> [  153.969008]  ? vfs_getattr_nosec+0x14a/0x190
>>>>>>> [  153.970539]  ? __do_sys_newfstat+0xd6/0xf0
>>>>>>> [  153.971713]  ? __ia32_compat_sys_newfstat+0x40/0x40
>>>>>>> [  153.973005]  ? __x64_sys_io_submit+0x125/0x3b0
>>>>>>> [  153.974282]  ? __ia32_sys_io_submit+0x390/0x390
>>>>>>> [  153.975575]  ? __kasan_check_read+0x1d/0x30
>>>>>>> [  153.976749]  ? do_syscall_64+0x35/0x80
>>>>>>> [  153.978034]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
>>>>>>> [  153.979436]
>>>>>>> [  153.979738] Allocated by task 726:
>>>>>>> [  153.980352]  kasan_save_stack+0x23/0x60
>>>>>>> [  153.981054]  set_alloc_info+0x46/0x70
>>>>>>> [  153.981745]  __kasan_slab_alloc+0x4c/0x90
>>>>>>> [  153.982492]  kmem_cache_alloc+0x153/0x750
>>>>>>> [  153.983953]  ovl_read_iter+0x13b/0x270
>>>>>>> [  153.984689]  aio_read+0x190/0x2d0
>>>>>>> [  153.985332]  io_submit_one+0xaa7/0x1480
>>>>>>> [  153.986060]  __x64_sys_io_submit+0x125/0x3b0
>>>>>>> [  153.986878]  do_syscall_64+0x35/0x80
>>>>>>> [  153.987590]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>>>>>>> [  153.988516]
>>>>>>> [  153.988824] Freed by task 750:
>>>>>>> [  153.989417]  kasan_save_stack+0x23/0x60
>>>>>>> [  153.990140]  kasan_set_track+0x24/0x40
>>>>>>> [  153.990871]  kasan_set_free_info+0x30/0x60
>>>>>>> [  153.991639]  __kasan_slab_free+0x137/0x210
>>>>>>> [  153.992390]  kmem_cache_free+0xf8/0x590
>>>>>>> [  153.993303]  ovl_aio_cleanup_handler+0x1ae/0x2a0
>>>>>>> [  153.994205]  ovl_aio_rw_complete+0x31/0x60
>>>>>>> [  153.995043]  iomap_dio_complete_work+0x4b/0x60
>>>>>>> [  153.995898]  iomap_dio_bio_end_io+0x23d/0x270
>>>>>>> [  153.996742]  bio_endio+0x40d/0x440
>>>>>>> [  153.997376]  blk_update_request+0x38f/0x820
>>>>>>> [  153.998160]  scsi_end_request+0x56/0x320
>>>>>>> [  153.998872]  scsi_io_completion+0x10a/0xb60
>>>>>>> [  153.999655]  scsi_finish_command+0x194/0x2b0
>>>>>>> [  154.000464]  scsi_complete+0xd7/0x1f0
>>>>>>> [  154.001184]  blk_complete_reqs+0x92/0xb0
>>>>>>> [  154.001930]  blk_done_softirq+0x29/0x40
>>>>>>> [  154.002696]  __do_softirq+0x133/0x57f
>>>>>>>
>>>>>>> ext4_dio_read_iter
>>>>>>>      ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0)
>>>>>>>      file_accessed(iocb->ki_filp) <== this trigger UAF
>>>>>>>
>>>>>>> Ret can be -EIOCBQUEUED which means we will not wait for io
>>>>>>> completion in
>>>>>>> iomap_dio_rw. So the release for ovl_aio_req will be done when io
>>>>>>> completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler
>>>>>>> in ovl_read_iter will do this). But once io finish soon, we may already
>>>>>>> release ovl_aio_req before we call file_access in ext4_dio_read_iter.
>>>>>>> This can trigger the upper UAF.
>>>>>>>
>>>>>>> Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did.
>>>>>>
>>>>>> Looks good at a glance.   Will review more fully.
>>>>>
>>>>> Hi,
>>>>>
>>>>> Any comments for this patch? :)
>>>
>>> Thanks for the patch.  I found one issue: the fdput() needs to be moved to the
>>> destruction as well, since the iocb->ki_filp reference comes from aio_req->fd.
>>
>> Hi, it seems we will only use aio_req->iocb in ovl_aio_cleanup_handler
>> before we call fdput(aio_req->fd):
> 
> Correct.  However I'm taking about this call:
> file_accessed(iocb->ki_filp).  If the fdput() is done from
> ovl_aio_cleanup_handler() which is called from ->ki_complete() then
> this would put the file, agains resulting in a UAF, only inside
> file_accessed() this time.   The reason why you weren't seeing this,
> is probably that most of the time aio_req->fd is from
> file->private_data, which is the real file obtained at open time, and
> which isn't actually closed at fdput() (flags == 0).

Thanks for your analysis. Got it now!

> 
>>
>> static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
>> {
>>           struct kiocb *iocb = &aio_req->iocb;
>>           struct kiocb *orig_iocb = aio_req->orig_iocb;
>>
>>           if (iocb->ki_flags & IOCB_WRITE) {
>>                   struct inode *inode = file_inode(orig_iocb->ki_filp);
>>
>>                   /* Actually acquired in ovl_write_iter() */
>>                   __sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb,
>>                                         SB_FREEZE_WRITE);
>>                   file_end_write(iocb->ki_filp);
>>                   <=== use iocb
>>                   ovl_copyattr(ovl_inode_real(inode), inode);
>>           }
>>
>>           orig_iocb->ki_pos = iocb->ki_pos;
>>           fdput(aio_req->fd); <=== release aio_req->fd
>>           kmem_cache_free(ovl_aio_request_cachep, aio_req);
>> }
>>
>> So call fdput(aio_req->fd) in ovl_aio_cleanup_handler or ovl_aio_put
>> seems all ok for me.
>>
>>>
>>> Other than that, it looks good.
>>>
>>> Minor things:
>>>
>>> - instead of setting refcount to 1 and incrementing it, just initialize it to 2
>>>
>>> - code deduplication can come after the fix (if at all), this helps backporting
>>
>> Agree.
>>
>>>
>>> - cleaned up header comment
>>>
>>> Here's the updated patch, can you please verify that I didn't break anything?
>>
>> Thanks! This patch can help pass the test!
> 
> Great, thanks.
> 
> Miklos
> .
>