CVE-2021-47510

In the Linux kernel, the following vulnerability has been resolved: btrfs:
fix re-dirty process of tree-log nodes There is a report of a transaction
abort of -EAGAIN with the following script. #!/bin/sh for d in sda sdb; do
mkfs.btrfs -d single -m single -f /dev/${d} done mount /dev/sda /mnt/test
mount /dev/sdb /mnt/scratch for dir in test scratch; do echo 3
>/proc/sys/vm/drop_caches fio --directory=/mnt/${dir} --name=fio.${dir}
–rw=read --size=50G --bs=64m \ –numjobs=$(nproc) --time_based
–ramp_time=5 --runtime=480 \ –group_reporting |& tee /dev/shm/fio.${dir}
echo 3 >/proc/sys/vm/drop_caches done for d in sda sdb; do umount
/dev/${d} done The stack trace is shown in below. [3310.967991] BTRFS:
error (device sda) in btrfs_commit_transaction:2341: errno=-11 unknown
(Error while writing out transaction) [3310.968060] BTRFS info (device
sda): forced readonly [3310.968064] BTRFS warning (device sda): Skipping
commit of aborted transaction. [3310.968065] ------------[ cut here
]------------ [3310.968066] BTRFS: Transaction aborted (error -11)
[3310.968074] WARNING: CPU: 14 PID: 1684 at fs/btrfs/transaction.c:1946
btrfs_commit_transaction.cold+0x209/0x2c8 [3310.968131] CPU: 14 PID: 1684
Comm: fio Not tainted 5.14.10-300.fc35.x86_64 #1 [3310.968135] Hardware
name: DIAWAY Tartu/Tartu, BIOS V2.01.B10 04/08/2021 [3310.968137] RIP:
0010:btrfs_commit_transaction.cold+0x209/0x2c8 [3310.968144] RSP:
0018:ffffb284ce393e10 EFLAGS: 00010282 [3310.968147] RAX: 0000000000000026
RBX: ffff973f147b0f60 RCX: 0000000000000027 [3310.968149] RDX:
ffff974ecf098a08 RSI: 0000000000000001 RDI: ffff974ecf098a00 [3310.968150]
RBP: ffff973f147b0f08 R08: 0000000000000000 R09: ffffb284ce393c48
[3310.968151] R10: ffffb284ce393c40 R11: ffffffff84f47468 R12:
ffff973f101bfc00 [3310.968153] R13: ffff971f20cf2000 R14: 00000000fffffff5
R15: ffff973f147b0e58 [3310.968154] FS: 00007efe65468740(0000)
GS:ffff974ecf080000(0000) knlGS:0000000000000000 [3310.968157] CS: 0010 DS:
0000 ES: 0000 CR0: 0000000080050033 [3310.968158] CR2: 000055691bcbe260
CR3: 000000105cfa4001 CR4: 0000000000770ee0 [3310.968160] PKRU: 55555554
[3310.968161] Call Trace: [3310.968167] ? dput+0xd4/0x300 [3310.968174]
btrfs_sync_file+0x3f1/0x490 [3310.968180] __x64_sys_fsync+0x33/0x60
[3310.968185] do_syscall_64+0x3b/0x90 [3310.968190]
entry_SYSCALL_64_after_hwframe+0x44/0xae [3310.968194] RIP:
0033:0x7efe6557329b [3310.968200] RSP: 002b:00007ffe0236ebc0 EFLAGS:
00000293 ORIG_RAX: 000000000000004a [3310.968203] RAX: ffffffffffffffda
RBX: 0000000000000000 RCX: 00007efe6557329b [3310.968204] RDX:
0000000000000000 RSI: 00007efe58d77010 RDI: 0000000000000006 [3310.968205]
RBP: 0000000004000000 R08: 0000000000000000 R09: 00007efe58d77010
[3310.968207] R10: 0000000016cacc0c R11: 0000000000000293 R12:
00007efe5ce95980 [3310.968208] R13: 0000000000000000 R14: 00007efe6447c790
R15: 0000000c80000000 [3310.968212] —[ end trace 1a346f4d3c0d96ba ]—
[3310.968214] BTRFS: error (device sda) in cleanup_transaction:1946:
errno=-11 unknown The abort occurs because of a write hole while writing
out freeing tree nodes of a tree-log tree. For zoned btrfs, we re-dirty a
freed tree node to ensure btrfs can write the region and does not leave a
hole on write on a zoned device. The current code fails to re-dirty a node
when the tree-log tree’s depth is greater or equal to 2. That leads to a
transaction abort with -EAGAIN. Fix the issue by properly re-dirtying a
node on walking up the tree.