From: yangerkun <yangerkun@huawei.com>
To: <miklos@szeredi.hu>, <amir73il@gmail.com>,
<jiufei.xue@linux.alibaba.com>
Cc: <linux-unionfs@vger.kernel.org>, <yukuai3@huawei.com>
Subject: Re: [PATCH 2/2] ovl: fix UAF for ovl_aio_req
Date: Fri, 8 Oct 2021 09:25:26 +0800 [thread overview]
Message-ID: <20d48554-c8b1-c761-6eac-307a09e7d5c7@huawei.com> (raw)
In-Reply-To: <20210930032228.3199690-3-yangerkun@huawei.com>
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);
> }
>
next prev parent reply other threads:[~2021-10-08 1:25 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-30 3:22 [PATCH 0/2] ovl: bugfix for ovl_aio_req yangerkun
2021-09-30 3:22 ` [PATCH 1/2] ovl: factor out ovl_get_aio_req yangerkun
2021-09-30 3:22 ` [PATCH 2/2] ovl: fix UAF for ovl_aio_req yangerkun
2021-10-08 1:25 ` yangerkun [this message]
2021-10-08 15:13 ` Miklos Szeredi
2021-10-18 14:26 ` yangerkun
2021-10-28 12:41 ` yangerkun
2021-10-29 8:35 ` Miklos Szeredi
2021-10-29 11:40 ` Miklos Szeredi
2021-11-01 4:02 ` yangerkun
2021-11-01 9:15 ` Miklos Szeredi
2021-11-01 10:52 ` yangerkun
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20d48554-c8b1-c761-6eac-307a09e7d5c7@huawei.com \
--to=yangerkun@huawei.com \
--cc=amir73il@gmail.com \
--cc=jiufei.xue@linux.alibaba.com \
--cc=linux-unionfs@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=yukuai3@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).