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CVE PROGRAM SOURCE RECORD7.8 High

CVE-2026-98116

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

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In 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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 33061d0fba51d2bf70a2ef9645f703c33fe8e438 to < e6cdd2a0470d64073349a970dc1691433804b271affected
  • 92ee3c60ec9fe64404dc035e7c41277d74aa26cb to < 9857a75714bb5df4781e4d8b1a1753b1e17bf07aaffected
  • 92ee3c60ec9fe64404dc035e7c41277d74aa26cb to < cbadf2575d25e7dcc0d4da2717817ae569fbc99baffected
  • 92ee3c60ec9fe64404dc035e7c41277d74aa26cb to < cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5affected
  • 92ee3c60ec9fe64404dc035e7c41277d74aa26cb to < fd137bf8149bc6460f9b7b1fc292025da04cb9eeaffected
  • 92ee3c60ec9fe64404dc035e7c41277d74aa26cb to < 8c1882dfee8f404d118020664b73eb4592172226affected
  • 92ee3c60ec9fe64404dc035e7c41277d74aa26cb to < 9b110a9dcecc59516c77cb3c0caf1f492f75df2daffected
  • a42aa926843acca96c0dfbde2e835b8137f2f092affected
  • 9cb6c40a6ebe4a0cfc9d6a181958211682cffea9affected
  • fbeb492694ce0441053de57699e1e2b7bc148a69affected
  • 0f6947f5f5208f6ebd4d76a82a4757e2839a23f8affected
  • 0090c13cbbdffd7da079ac56f80373a9a1be0bf8affected
  • 1bbf82d9f961414d6c76a08f7f843ea068e0ab7baffected
  • 5.15.32 to < 5.15.222affected
  • 4.14.279 to < 4.15affected
  • 4.19.243 to < 4.20affected
  • 5.4.193 to < 5.5affected
  • 5.10.109 to < 5.11affected
  • 5.16.18 to < 5.17affected
  • 5.17.1 to < 5.18affected

Linux Linux

Default version status: affected

  • 5.18affected
  • 0 to < 5.18unaffected
  • 5.15.222 to ≤ 5.15.*unaffected
  • 6.1.189 to ≤ 6.1.*unaffected
  • 6.6.158 to ≤ 6.6.*unaffected
  • 6.12.111 to ≤ 6.12.*unaffected
  • 6.18.53 to ≤ 6.18.*unaffected
  • 7.2.7 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References