| Summary: |
VUL-0: CVE-2024-35798: kernel: btrfs: fix race in read_extent_buffer_pages() |
| Product: |
[Novell Products] SUSE Security Incidents
|
Reporter: |
SMASH SMASH <smash_bz> |
| Component: |
Incidents | Assignee: |
Security Team bot <security-team> |
| Status: |
RESOLVED
FIXED
|
QA Contact: |
Security Team bot <security-team> |
| Severity: |
Normal
|
|
|
| Priority: |
P3 - Medium
|
CC: |
gabriele.sonnu, jlee, vasant.karasulli
|
| Version: |
unspecified | |
|
| Target Milestone: |
--- | |
|
| Hardware: |
Other | |
|
| OS: |
Other | |
|
| URL: |
https://smash.suse.de/issue/406469/
|
| Whiteboard: |
CVSSv3.1:SUSE:CVE-2024-35798:5.5:(AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) |
|
Found By:
|
Security Response Team
|
Services Priority:
|
|
|---|
|
Business Priority:
|
|
Blocker:
|
---
|
|---|
|
Marketing QA Status:
|
---
|
IT Deployment:
|
---
|
|---|
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: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-35798 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-35798.mbox https://git.kernel.org/stable/c/0427c8ef8bbb7f304de42ef51d69c960e165e052 https://git.kernel.org/stable/c/3a25878a3378adce5d846300c9570f15aa7f7a80 https://git.kernel.org/stable/c/2885d54af2c2e1d910e20d5c8045bae40e02fbc1 https://git.kernel.org/stable/c/ef1e68236b9153c27cb7cf29ead0c532870d4215 https://www.cve.org/CVERecord?id=CVE-2024-35798 https://bugzilla.redhat.com/show_bug.cgi?id=2281241