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CVE-2026-89796

mm/damon/core: avoid infinite kdamond_merge_regions() internal loop

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.15.222, 6.1.189, 6.6.158, 6.10, 6.12.111, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

In the Linux kernel, the following vulnerability has been resolved: mm/damon/core: avoid infinite kdamond_merge_regions() internal loop Patch series "mm/damon: unurgent fixes for infinite loop, NULL de-ref and races", v1.1. Sashiko found a few issues in DAMON that could cause infinite loop, NULL dereference and monitoring results degradation. The first two sounds scary but the infinite loop happens only under unreasonable user setup. The NULL dereference is only in a unit test. Monitoring results degradation is trivial since it is only best-effort, and those happens from only unlikely races. Still those are bugs that better to fix if possible. Fix those. This patch (of 6): Due to online parameter update like events, the number of DAMON regions could be higher than the user-set upper limit. kdamond_merge_regions() repeats merge regions until the number meets the limit, while doubling the merge threshold up to the theoretical maximum threshold. It is tried only up to the theoretical maximum threshold because even the aggressive merging can fail from reducing the number of regions under the user-defined upper limit. For example, there could be many user-defined non-contiguous regions that cannot be merged. The threshold based loop break condition is evaluated by comparing the threshold for the next merging try against the theoretical maximum threshold. If max_thres is larger than UINT_MAX / 2, doubling the threshold could make it overflow, and bypass the loop break condition. In the case, if the number of regions cannot be reduced under the upper limit like explained above, the loop will run infinitely. Prevent the case by doing the break condition check before doubling the threshold. Also, prevent the threshold exceeding the maximum threshold, as it could overflow and apply the wrong merge threshold. This issue is unlikely to occur in real world, since having the max_thres higher than UINT_MAX / 2 require unrealistically large aggregation intervals compared to the sampling interval. Also, it requires an unrealistically large number of uncontiguous regions setup. Nonetheless, the consequence is bad and the fix is simple. The issue was discovered [1] by Sashiko.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 1e865019cef354a5f0314491b4b4fc9f9a613642 · fixed in 407da1dd7f48e5ba22ceb8834f6923390632d025; From d7eda72e59bbf3ed592db7ff0fd8c246c73149a8 · fixed in 65edd8b3a88278c9f8e5c7d8c15d4f296ce35078; From 11078e2d11465518a9e85096bd28f8cd5fa1ea41 · fixed in 5b0953f86d65855dc901050f40bbe6da0475d198; From 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6 · fixed in 769c16699c89811386eb003c8fd9dcb8d405b316; From 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6 · fixed in 50a7a5aec1aa43efc297fd4377c1cbdc7d15620d; From 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6 · fixed in 8a96a06e04d210845be5d9581c0e9e338947e8f8; From 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6 · fixed in 123e4619ab6c8ab1c4cb1d7a58311a2af13929cd; From 5.15.164 · fixed in 5.15.222; From 6.1.101 · fixed in 6.1.189; From 6.6.41 · fixed in 6.6.158; From 6.9.10 · fixed in 6.10

  • Linux Linux

    6.10

  • KernelLinux

    fixed in 5.15.222; From 5.16.0 · fixed in 6.1.189; From 6.2.0 · fixed in 6.6.158; From 6.7.0 · fixed in 6.12.111; From 6.10.0 · fixed in 6.18.53; From 6.13.0 · fixed in 7.2.5

References 7

git.kernel.org