CVE-2024-35798 Affecting kernel-rt-kvm package, versions *
Threat Intelligence
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Test your applications- Snyk IDSNYK-CENTOS7-KERNELRTKVM-6881523
- published18 May 2024
- disclosed17 May 2024
Introduced: 17 May 2024
CVE-2024-35798 (opens in a new tab)How to fix?
There is no fixed version for Centos:7 kernel-rt-kvm.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-rt-kvm package and not the kernel-rt-kvm package as distributed by Centos.
See How to fix? for Centos:7 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix race in read_extent_buffer_pages()
There are reports from tree-checker that detects corrupted nodes, without any obvious pattern so possibly an overwrite in memory. After some debugging it turns out there's a race when reading an extent buffer the uptodate status can be missed.
To prevent concurrent reads for the same extent buffer, read_extent_buffer_pages() performs these checks:
/* (1) */ if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) return 0;
/* (2) */ if (test_and_set_bit(EXTENT_BUFFER_READING, &eb->bflags)) goto done;
At this point, it seems safe to start the actual read operation. Once that completes, end_bbio_meta_read() does
/* (3) */ set_extent_buffer_uptodate(eb);
/* (4) */ clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
Normally, this is enough to ensure only one read happens, and all other callers wait for it to finish before returning. Unfortunately, there is a racey interleaving:
Thread A | Thread B | Thread C
---------+----------+---------
(1) | |
| (1) |
(2) | |
(3) | |
(4) | |
| (2) |
| | (1)
When this happens, thread B kicks of an unnecessary read. Worse, thread C will see UPTODATE set and return immediately, while the read from thread B is still in progress. This race could result in tree-checker errors like this as the extent buffer is concurrently modified:
BTRFS critical (device dm-0): corrupted node, root=256
block=8550954455682405139 owner mismatch, have 11858205567642294356
expect [256, 18446744073709551360]
Fix it by testing UPTODATE again after setting the READING bit, and if it's been set, skip the unnecessary read.
[ minor update of changelog ]
References
- https://access.redhat.com/security/cve/CVE-2024-35798
- https://git.kernel.org/stable/c/0427c8ef8bbb7f304de42ef51d69c960e165e052
- https://git.kernel.org/stable/c/2885d54af2c2e1d910e20d5c8045bae40e02fbc1
- https://git.kernel.org/stable/c/3a25878a3378adce5d846300c9570f15aa7f7a80
- https://git.kernel.org/stable/c/ef1e68236b9153c27cb7cf29ead0c532870d4215