ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF

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Summary

CVECVE-2026-98116
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 11:17:42 UTC
Updated2026-09-25 11:17:42 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF snd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation with an mmap_count check performed under the PCM stream lock, but the lock is released long before the buffer is actually freed: snd_pcm_sync_stop(), constraint refinement and do_free_pages() all happen in between. snd_pcm_mmap_data(), on the other hand, takes no lock at all: it validates against the old buffer's state and dma_bytes, remaps its pages into the VMA, and only then increments mmap_count. A concurrent mmap() can therefore slip in between the check and the free. remap_pfn_range() installs writable PTEs for the old buffer's pages without taking page references, and the subsequent do_free_pages() returns those pages to the page allocator while the VMA still maps them. This leaves a stale, writable mapping of freed pages: a page-level use-after-free that can be leveraged for local privilege escalation. Make snd_pcm_mmap_data() participate in the buffer-access scheme introduced for hw_params/hw_free: acquire runtime->buffer_accessing before validating and remapping, and release it afterwards. Buffer reallocation already fails with -EBUSY while accessors are active, and the mmap side now fails with -EBUSY while a reallocation is in progress, so the validate/remap sequence and the check/free sequence can no longer interleave. A reproducer that turns this race into a stale writable mapping of the freed DMA buffer pages is available on request.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5 git Not specified
CNA Linux Linux affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb fd137bf8149bc6460f9b7b1fc292025da04cb9ee git Not specified
CNA Linux Linux affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb 8c1882dfee8f404d118020664b73eb4592172226 git Not specified
CNA Linux Linux affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb 9b110a9dcecc59516c77cb3c0caf1f492f75df2d git Not specified
CNA Linux Linux affected a42aa926843acca96c0dfbde2e835b8137f2f092 git Not specified
CNA Linux Linux affected 9cb6c40a6ebe4a0cfc9d6a181958211682cffea9 git Not specified
CNA Linux Linux affected fbeb492694ce0441053de57699e1e2b7bc148a69 git Not specified
CNA Linux Linux affected 0f6947f5f5208f6ebd4d76a82a4757e2839a23f8 git Not specified
CNA Linux Linux affected 33061d0fba51d2bf70a2ef9645f703c33fe8e438 git Not specified
CNA Linux Linux affected 0090c13cbbdffd7da079ac56f80373a9a1be0bf8 git Not specified
CNA Linux Linux affected 1bbf82d9f961414d6c76a08f7f843ea068e0ab7b git Not specified
CNA Linux Linux affected 4.14.279 4.15 semver Not specified
CNA Linux Linux affected 4.19.243 4.20 semver Not specified
CNA Linux Linux affected 5.4.193 5.5 semver Not specified
CNA Linux Linux affected 5.10.109 5.11 semver Not specified
CNA Linux Linux affected 5.15.32 5.16 semver Not specified
CNA Linux Linux affected 5.16.18 5.17 semver Not specified
CNA Linux Linux affected 5.17.1 5.18 semver Not specified
CNA Linux Linux affected 5.18 Not specified
CNA Linux Linux unaffected 5.18 semver Not specified
CNA Linux Linux unaffected 6.12.111 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.53 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.7 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fd137bf8149bc6460f9b7b1fc292025da04cb9ee 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8c1882dfee8f404d118020664b73eb4592172226 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9b110a9dcecc59516c77cb3c0caf1f492f75df2d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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