From: Anand Jain anand.jain@oracle.com
commit 16a200f66ede3f9afa2e51d90ade017aaa18d213 upstream.
A fstrim on a degraded raid1 can trigger the following null pointer dereference:
BTRFS info (device loop0): allowing degraded mounts BTRFS info (device loop0): disk space caching is enabled BTRFS info (device loop0): has skinny extents BTRFS warning (device loop0): devid 2 uuid 97ac16f7-e14d-4db1-95bc-3d489b424adb is missing BTRFS warning (device loop0): devid 2 uuid 97ac16f7-e14d-4db1-95bc-3d489b424adb is missing BTRFS info (device loop0): enabling ssd optimizations BUG: kernel NULL pointer dereference, address: 0000000000000620 PGD 0 P4D 0 Oops: 0000 [#1] SMP NOPTI CPU: 0 PID: 4574 Comm: fstrim Not tainted 5.13.0-rc7+ #31 Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 RIP: 0010:btrfs_trim_fs+0x199/0x4a0 [btrfs] RSP: 0018:ffff959541797d28 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff946f84eca508 RCX: a7a67937adff8608 RDX: ffff946e8122d000 RSI: 0000000000000000 RDI: ffffffffc02fdbf0 RBP: ffff946ea4615000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: ffff946e8122d960 R12: 0000000000000000 R13: ffff959541797db8 R14: ffff946e8122d000 R15: ffff959541797db8 FS: 00007f55917a5080(0000) GS:ffff946f9bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000620 CR3: 000000002d2c8001 CR4: 00000000000706f0 Call Trace: btrfs_ioctl_fitrim+0x167/0x260 [btrfs] btrfs_ioctl+0x1c00/0x2fe0 [btrfs] ? selinux_file_ioctl+0x140/0x240 ? syscall_trace_enter.constprop.0+0x188/0x240 ? __x64_sys_ioctl+0x83/0xb0 __x64_sys_ioctl+0x83/0xb0
Reproducer:
$ mkfs.btrfs -fq -d raid1 -m raid1 /dev/loop0 /dev/loop1 $ mount /dev/loop0 /btrfs $ umount /btrfs $ btrfs dev scan --forget $ mount -o degraded /dev/loop0 /btrfs
$ fstrim /btrfs
The reason is we call btrfs_trim_free_extents() for the missing device, which uses device->bdev (NULL for missing device) to find if the device supports discard.
Fix is to check if the device is missing before calling btrfs_trim_free_extents().
CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Anand Jain anand.jain@oracle.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/extent-tree.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -5883,6 +5883,9 @@ int btrfs_trim_fs(struct btrfs_fs_info * mutex_lock(&fs_info->fs_devices->device_list_mutex); devices = &fs_info->fs_devices->devices; list_for_each_entry(device, devices, dev_list) { + if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) + continue; + ret = btrfs_trim_free_extents(device, &group_trimmed); if (ret) { dev_failed++;