CVE-2021-47510
Description
From CVE.org
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.
Statement
Red Hat Enterprise Linux is not vulnerable to this CVE, as it does not affect the versions or configurations of the Linux kernel used in its distributions.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Other
Technical Impact: Alter Execution Logic
An attacker could cause the product to skip critical steps or perform them in the wrong order, bypassing its intended business logic. This can sometimes have security implications.
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