CVE-2022-48833 btrfs: skip reserved bytes warning on unmount after log cleanup failure

What is CVE-2022-48833?

CVE-2022-48833 is a medium-severity denial of service vulnerability in Linux kernel, published on 16 Jul 2024. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

btrfs: skip reserved bytes warning on unmount after log cleanup failure

After the recent changes made by commit c2e39305299f01 ("btrfs: clear extent buffer uptodate when we fail to write it") and its followup fix, commit 651740a5024117 ("btrfs: check WRITE_ERR when trying to read an extent buffer"), we can now end up not cleaning up space reservations of log tree extent buffers after a transaction abort happens, as well as not cleaning up still dirty extent buffers.

This happens because if writeback for a log tree extent buffer failed, then we have cleared the bit EXTENT_BUFFER_UPTODATE from the extent buffer and we have also set the bit EXTENT_BUFFER_WRITE_ERR on it. Later on, when trying to free the log tree with free_log_tree(), which iterates over the tree, we can end up getting an -EIO error when trying to read a node or a leaf, since read_extent_buffer_pages() returns -EIO if an extent buffer does not have EXTENT_BUFFER_UPTODATE set and has the EXTENT_BUFFER_WRITE_ERR bit set. Getting that -EIO means that we return immediately as we can not iterate over the entire tree.

In that case we never update the reserved space for an extent buffer in the respective block group and space_info object.

When this happens we get the following traces when unmounting the fs:

[174957.284509] BTRFS: error (device dm-0) in cleanup_transaction:1913: errno=-5 IO failure [174957.286497] BTRFS: error (device dm-0) in free_log_tree:3420: errno=-5 IO failure [174957.399379] ------------[ cut here ]------------ [174957.402497] WARNING: CPU: 2 PID: 3206883 at fs/btrfs/block-group.c:127 btrfs_put_block_group+0x77/0xb0 [btrfs] [174957.407523] Modules linked in: btrfs overlay dm_zero (...) [174957.424917] CPU: 2 PID: 3206883 Comm: umount Tainted: G W 5.16.0-rc5-btrfs-next-109 #1 [174957.426689] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [174957.428716] RIP: 0010:btrfs_put_block_group+0x77/0xb0 [btrfs] [174957.429717] Code: 21 48 8b bd (...) [174957.432867] RSP: 0018:ffffb70d41cffdd0 EFLAGS: 00010206 [174957.433632] RAX: 0000000000000001 RBX: ffff8b09c3848000 RCX: ffff8b0758edd1c8 [174957.434689] RDX: 0000000000000001 RSI: ffffffffc0b467e7 RDI: ffff8b0758edd000 [174957.436068] RBP: ffff8b0758edd000 R08: 0000000000000000 R09: 0000000000000000 [174957.437114] R10: 0000000000000246 R11: 0000000000000000 R12: ffff8b09c3848148 [174957.438140] R13: ffff8b09c3848198 R14: ffff8b0758edd188 R15: dead000000000100 [174957.439317] FS: 00007f328fb82800(0000) GS:ffff8b0a2d200000(0000) knlGS:0000000000000000 [174957.440402] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [174957.441164] CR2: 00007fff13563e98 CR3: 0000000404f4e005 CR4: 0000000000370ee0 [174957.442117] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [174957.443076] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [174957.443948] Call Trace: [174957.444264] <TASK> [174957.444538] btrfs_free_block_groups+0x255/0x3c0 [btrfs] [174957.445238] close_ctree+0x301/0x357 [btrfs] [174957.445803] ? call_rcu+0x16c/0x290 [174957.446250] generic_shutdown_super+0x74/0x120 [174957.446832] kill_anon_super+0x14/0x30 [174957.447305] btrfs_kill_super+0x12/0x20 [btrfs] [174957.447890] deactivate_locked_super+0x31/0xa0 [174957.448440] cleanup_mnt+0x147/0x1c0 [174957.448888] task_work_run+0x5c/0xa0 [174957.449336] exit_to_user_mode_prepare+0x1e5/0x1f0 [174957.449934] syscall_exit_to_user_mode+0x16/0x40 [174957.450512] do_syscall_64+0x48/0xc0 [174957.450980] entry_SYSCALL_64_after_hwframe+0x44/0xae [174957.451605] RIP: 0033:0x7f328fdc4a97 [174957.452059] Code: 03 0c 00 f7 (...) [174957.454320] RSP: 002b:00007fff13564ec8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 [174957.455262] RAX: 0000000000000000 RBX: 00007f328feea264 RCX: 00007f328fdc4a97 [174957.456131] RDX: 0000000000000000 RSI: 00000000000000 ---truncated---

Which versions are affected by CVE-2022-48833?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2022-48833?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2022-48833 being exploited?

There is no known exploitation of CVE-2022-48833 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-68246, DEBIAN-CVE-2022-48833, GHSA-vp69-366h-2hqh, ROOT-OS-DEBIAN-11-CVE-2022-48833, UBUNTU-CVE-2022-48833.