diff options
| author | Qu Wenruo <wqu@suse.com> | 2021-08-06 18:24:15 +0800 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2021-08-23 13:19:11 +0200 |
| commit | e4571b8c5e9ffa1e85c0c671995bd4dcc5c75091 (patch) | |
| tree | 07dddf4e27d6c5d9b1b9bcd6c000aacfe6c21e86 /fs/btrfs | |
| parent | 63fb5879db7ca94fefac12cf7a5a051cee889c12 (diff) | |
btrfs: fix NULL pointer dereference when deleting device by invalid id
[BUG]
It's easy to trigger NULL pointer dereference, just by removing a
non-existing 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")
CC: stable@vger.kernel.org # 5.4+
Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/volumes.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 536e60c6ade3..7fec0c68b744 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2074,7 +2074,7 @@ 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); |