@@ -91,6 +91,17 @@ int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
if (ret) {
no_valid_dev_replace_entry_found:
+ /*
+ * We don't have a replace item or it's corrupted.
+ * If there is a replace target, fail the mount.
+ */
+ if (btrfs_find_device(fs_info->fs_devices,
+ BTRFS_DEV_REPLACE_DEVID, NULL, NULL)) {
+ btrfs_err(fs_info,
+ "found replace target device without a replace item");
+ ret = -EIO;
+ goto out;
+ }
ret = 0;
dev_replace->replace_state =
BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
@@ -143,8 +154,19 @@ int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
- dev_replace->srcdev = NULL;
- dev_replace->tgtdev = NULL;
+ /*
+ * We don't have an active replace item but if there is a
+ * replace target, fail the mount.
+ */
+ if (btrfs_find_device(fs_info->fs_devices,
+ BTRFS_DEV_REPLACE_DEVID, NULL, NULL)) {
+ btrfs_err(fs_info,
+ "replace devid present without an active replace item");
+ ret = -EIO;
+ } else {
+ dev_replace->srcdev = NULL;
+ dev_replace->tgtdev = NULL;
+ }
break;
case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
@@ -1056,22 +1056,13 @@ static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices,
continue;
}
- if (device->devid == BTRFS_DEV_REPLACE_DEVID) {
- /*
- * In the first step, keep the device which has
- * the correct fsid and the devid that is used
- * for the dev_replace procedure.
- * In the second step, the dev_replace state is
- * read from the device tree and it is known
- * whether the procedure is really active or
- * not, which means whether this device is
- * used or whether it should be removed.
- */
- if (step == 0 || test_bit(BTRFS_DEV_STATE_REPLACE_TGT,
- &device->dev_state)) {
- continue;
- }
- }
+ /*
+ * We have already validated the presence of BTRFS_DEV_REPLACE_DEVID,
+ * in btrfs_init_dev_replace() so just continue.
+ */
+ if (device->devid == BTRFS_DEV_REPLACE_DEVID)
+ continue;
+
if (device->bdev) {
blkdev_put(device->bdev, device->mode);
device->bdev = NULL;
@@ -1080,9 +1071,6 @@ static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices,
if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
list_del_init(&device->dev_alloc_list);
clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
- if (!test_bit(BTRFS_DEV_STATE_REPLACE_TGT,
- &device->dev_state))
- fs_devices->rw_devices--;
}
list_del_init(&device->dev_list);
fs_devices->num_devices--;
If there is a BTRFS_DEV_REPLACE_DEVID without a replace item, then it means some device is trying to attack or may be corrupted. Fail the mount so that the user can remove the attacking or fix the corrupted device. As of now if BTRFS_DEV_REPLACE_DEVID is present without the replace item, in __btrfs_free_extra_devids() we determine that there is an extra device, and free those extra devices but continue to mount the device. However, we were wrong in keeping tack of the rw_devices so the syzbot testcase failed as below [1]. [1] WARNING: CPU: 1 PID: 3612 at fs/btrfs/volumes.c:1166 close_fs_devices.part.0+0x607/0x800 fs/btrfs/volumes.c:1166 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 3612 Comm: syz-executor.2 Not tainted 5.9.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x198/0x1fd lib/dump_stack.c:118 panic+0x347/0x7c0 kernel/panic.c:231 __warn.cold+0x20/0x46 kernel/panic.c:600 report_bug+0x1bd/0x210 lib/bug.c:198 handle_bug+0x38/0x90 arch/x86/kernel/traps.c:234 exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:254 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536 RIP: 0010:close_fs_devices.part.0+0x607/0x800 fs/btrfs/volumes.c:1166 Code: 0f b6 04 02 84 c0 74 02 7e 33 48 8b 44 24 18 c6 80 30 01 00 00 00 48 83 c4 30 5b 5d 41 5c 41 5d 41 5e 41 5f c3 e8 99 ce 6a fe <0f> 0b e9 71 ff ff ff e8 8d ce 6a fe 0f 0b e9 20 ff ff ff e8 d1 d5 RSP: 0018:ffffc900091777e0 EFLAGS: 00010246 RAX: 0000000000040000 RBX: ffffffffffffffff RCX: ffffc9000c8b7000 RDX: 0000000000040000 RSI: ffffffff83097f47 RDI: 0000000000000007 RBP: dffffc0000000000 R08: 0000000000000001 R09: ffff8880988a187f R10: 0000000000000000 R11: 0000000000000001 R12: ffff88809593a130 R13: ffff88809593a1ec R14: ffff8880988a1908 R15: ffff88809593a050 close_fs_devices fs/btrfs/volumes.c:1193 [inline] btrfs_close_devices+0x95/0x1f0 fs/btrfs/volumes.c:1179 open_ctree+0x4984/0x4a2d fs/btrfs/disk-io.c:3434 btrfs_fill_super fs/btrfs/super.c:1316 [inline] btrfs_mount_root.cold+0x14/0x165 fs/btrfs/super.c:1672 The fix here is, when we determine that there isn't a replace item then fail the mount if there is a replace target device (devid 0). The reproducer and the fix looks like this. mkfs.btrfs -fq /dev/sda dd if=/dev/sda of=/dev/sdb bs=1 seek=64K skip=64K count=4096 btrfs-sb-mod /dev/sdb dev_item.devid =0 mount -o device=/dev/sdb /dev/sda /btrfsS mount: /btrfs: wrong fs type, bad option, bad superblock on /dev/sda, missing codepage or helper program, or other error. [ 3526.708108] BTRFS error (device sdb): found replace target device without a replace item [ 3526.709152] BTRFS error (device sdb): failed to init dev_replace: -5 [ 3526.715623] BTRFS error (device sdb): open_ctree failed Cc: josef@toxicpanda.com Reported-by: syzbot+4cfe71a4da060be47502@syzkaller.appspotmail.com Signed-off-by: Anand Jain <anand.jain@oracle.com> --- (changle log reproducer updated). Conflicts with the patches btrfs: drop never met condition of disk_total_bytes == 0 btrfs: fix btrfs_find_device unused arg seed If these patches aren't integrated yet, then please add the last arg in the function btrfs_find_device(). Any value is fine as it doesn't care. Dropped the idea of fstests for now as the test case requires btrfs-sb-mod. And there aren't any fstests yet which shall carry 4k superblock in its script not sure if it's a good idea. Instead, we could rely on sysbot for now. v2: changed title old: btrfs: fix rw_devices count in __btrfs_free_extra_devids In btrfs_init_dev_replace() try to match the presence of replace_item to the BTRFS_DEV_REPLACE_DEVID device. If fails then fail the mount. So drop the similar check in __btrfs_free_extra_devids(). fs/btrfs/dev-replace.c | 26 ++++++++++++++++++++++++-- fs/btrfs/volumes.c | 26 +++++++------------------- 2 files changed, 31 insertions(+), 21 deletions(-)