[PATCH 5.4 091/108] btrfs: check for missing device in btrfs_trim_fs

Greg Kroah-Hartman
2021-07-26T16:13:32Z

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
@@ -5768,6 +5768,9 @@ 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++;