* [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id
@ 2021-08-06 10:24 Qu Wenruo
2021-08-10 14:23 ` David Sterba
2021-08-10 15:57 ` Anand Jain
0 siblings, 2 replies; 3+ messages in thread
From: Qu Wenruo @ 2021-08-06 10:24 UTC (permalink / raw)
To: linux-btrfs; +Cc: butt3rflyh4ck
[BUG]
It's super easy to trigger NULL pointer dereference, just by removing a
non-exist device id:
# mkfs.btrfs -f -m single -d single /dev/test/scratch1 \
/dev/test/scratch2
# mount /dev/test/scratch1 /mnt/btrfs
# btrfs device remove 3 /mnt/btrfs
Then we have the following kernel NULL pointer dereference:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 9 PID: 649 Comm: btrfs Not tainted 5.14.0-rc3-custom+ #35
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:btrfs_rm_device+0x4de/0x6b0 [btrfs]
btrfs_ioctl+0x18bb/0x3190 [btrfs]
? lock_is_held_type+0xa5/0x120
? find_held_lock.constprop.0+0x2b/0x80
? do_user_addr_fault+0x201/0x6a0
? lock_release+0xd2/0x2d0
? __x64_sys_ioctl+0x83/0xb0
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
[CAUSE]
Commit a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return
btrfs_device directly") moves the "missing" device path check into
btrfs_rm_device().
But btrfs_rm_device() itself can have case where it only receives
@devid, with NULL as @device_path.
In that case, calling strcmp() on NULL will trigger the NULL pointer
dereference.
Before that commit, we handle the "missing" case inside
btrfs_find_device_by_devspec(), which will not check @device_path at all
if @devid is provided, thus no way to trigger the bug.
[FIX]
Before calling strcmp(), also make sure @device_path is not NULL.
Fixes: a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return btrfs_device directly")
Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/volumes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 230192d097c4..5156254a9655 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2079,7 +2079,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
if (IS_ERR(device)) {
if (PTR_ERR(device) == -ENOENT &&
- strcmp(device_path, "missing") == 0)
+ device_path && strcmp(device_path, "missing") == 0)
ret = BTRFS_ERROR_DEV_MISSING_NOT_FOUND;
else
ret = PTR_ERR(device);
--
2.32.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id
2021-08-06 10:24 [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id Qu Wenruo
@ 2021-08-10 14:23 ` David Sterba
2021-08-10 15:57 ` Anand Jain
1 sibling, 0 replies; 3+ messages in thread
From: David Sterba @ 2021-08-10 14:23 UTC (permalink / raw)
To: Qu Wenruo; +Cc: linux-btrfs, butt3rflyh4ck
On Fri, Aug 06, 2021 at 06:24:15PM +0800, Qu Wenruo wrote:
> [BUG]
> It's super easy to trigger NULL pointer dereference, just by removing a
> non-exist device id:
>
> # mkfs.btrfs -f -m single -d single /dev/test/scratch1 \
> /dev/test/scratch2
> # mount /dev/test/scratch1 /mnt/btrfs
> # btrfs device remove 3 /mnt/btrfs
>
> Then we have the following kernel NULL pointer dereference:
>
> BUG: kernel NULL pointer dereference, address: 0000000000000000
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 9 PID: 649 Comm: btrfs Not tainted 5.14.0-rc3-custom+ #35
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> RIP: 0010:btrfs_rm_device+0x4de/0x6b0 [btrfs]
> btrfs_ioctl+0x18bb/0x3190 [btrfs]
> ? lock_is_held_type+0xa5/0x120
> ? find_held_lock.constprop.0+0x2b/0x80
> ? do_user_addr_fault+0x201/0x6a0
> ? lock_release+0xd2/0x2d0
> ? __x64_sys_ioctl+0x83/0xb0
> __x64_sys_ioctl+0x83/0xb0
> do_syscall_64+0x3b/0x90
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> [CAUSE]
> Commit a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return
> btrfs_device directly") moves the "missing" device path check into
> btrfs_rm_device().
>
> But btrfs_rm_device() itself can have case where it only receives
> @devid, with NULL as @device_path.
>
> In that case, calling strcmp() on NULL will trigger the NULL pointer
> dereference.
>
> Before that commit, we handle the "missing" case inside
> btrfs_find_device_by_devspec(), which will not check @device_path at all
> if @devid is provided, thus no way to trigger the bug.
>
> [FIX]
> Before calling strcmp(), also make sure @device_path is not NULL.
>
> Fixes: a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return btrfs_device directly")
> Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
Thanks for the report and fix, added to misc-next.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id
2021-08-06 10:24 [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id Qu Wenruo
2021-08-10 14:23 ` David Sterba
@ 2021-08-10 15:57 ` Anand Jain
1 sibling, 0 replies; 3+ messages in thread
From: Anand Jain @ 2021-08-10 15:57 UTC (permalink / raw)
To: Qu Wenruo, linux-btrfs; +Cc: butt3rflyh4ck
On 06/08/2021 18:24, Qu Wenruo wrote:
> [BUG]
> It's super easy to trigger NULL pointer dereference, just by removing a
> non-exist device id:
>
> # mkfs.btrfs -f -m single -d single /dev/test/scratch1 \
> /dev/test/scratch2
> # mount /dev/test/scratch1 /mnt/btrfs
> # btrfs device remove 3 /mnt/btrfs
>
> Then we have the following kernel NULL pointer dereference:
>
> BUG: kernel NULL pointer dereference, address: 0000000000000000
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 9 PID: 649 Comm: btrfs Not tainted 5.14.0-rc3-custom+ #35
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> RIP: 0010:btrfs_rm_device+0x4de/0x6b0 [btrfs]
> btrfs_ioctl+0x18bb/0x3190 [btrfs]
> ? lock_is_held_type+0xa5/0x120
> ? find_held_lock.constprop.0+0x2b/0x80
> ? do_user_addr_fault+0x201/0x6a0
> ? lock_release+0xd2/0x2d0
> ? __x64_sys_ioctl+0x83/0xb0
> __x64_sys_ioctl+0x83/0xb0
> do_syscall_64+0x3b/0x90
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> [CAUSE]
> Commit a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return
> btrfs_device directly") moves the "missing" device path check into
> btrfs_rm_device().
>
> But btrfs_rm_device() itself can have case where it only receives
> @devid, with NULL as @device_path.
>
> In that case, calling strcmp() on NULL will trigger the NULL pointer
> dereference.
>
> Before that commit, we handle the "missing" case inside
> btrfs_find_device_by_devspec(), which will not check @device_path at all
> if @devid is provided, thus no way to trigger the bug.
>
> [FIX]
> Before calling strcmp(), also make sure @device_path is not NULL.
>
> Fixes: a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return btrfs_device directly")
> Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
> ---
> fs/btrfs/volumes.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 230192d097c4..5156254a9655 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -2079,7 +2079,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
>
> if (IS_ERR(device)) {
> if (PTR_ERR(device) == -ENOENT &&
> - strcmp(device_path, "missing") == 0)
> + device_path && strcmp(device_path, "missing") == 0)
> ret = BTRFS_ERROR_DEV_MISSING_NOT_FOUND;
> else
> ret = PTR_ERR(device);
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-08-06 10:24 [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id Qu Wenruo
2021-08-10 14:23 ` David Sterba
2021-08-10 15:57 ` Anand Jain
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