{"id":"CVE-2026-98116","state":"PUBLISHED","title":"ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF\n\nsnd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation\nwith an mmap_count check performed under the PCM stream lock, but the\nlock is released long before the buffer is actually freed:\nsnd_pcm_sync_stop(), constraint refinement and do_free_pages() all\nhappen in between.  snd_pcm_mmap_data(), on the other hand, takes no\nlock at all: it validates against the old buffer's state and\ndma_bytes, remaps its pages into the VMA, and only then increments\nmmap_count.\n\nA concurrent mmap() can therefore slip in between the check and the\nfree.  remap_pfn_range() installs writable PTEs for the old buffer's\npages without taking page references, and the subsequent\ndo_free_pages() returns those pages to the page allocator while the\nVMA still maps them.  This leaves a stale, writable mapping of freed\npages: a page-level use-after-free that can be leveraged for local\nprivilege escalation.\n\nMake snd_pcm_mmap_data() participate in the buffer-access scheme\nintroduced for hw_params/hw_free: acquire runtime->buffer_accessing\nbefore validating and remapping, and release it afterwards.  Buffer\nreallocation already fails with -EBUSY while accessors are active,\nand the mmap side now fails with -EBUSY while a reallocation is in\nprogress, so the validate/remap sequence and the check/free sequence\ncan no longer interleave.\n\nA reproducer that turns this race into a stale writable mapping of\nthe freed DMA buffer pages is available on request.","publishedAt":"2026-09-25T10:36:01.723Z","updatedAt":"2026-10-19T09:14:08.504Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"33061d0fba51d2bf70a2ef9645f703c33fe8e438","status":"affected","lessThan":"e6cdd2a0470d64073349a970dc1691433804b271","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"9857a75714bb5df4781e4d8b1a1753b1e17bf07a","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"cbadf2575d25e7dcc0d4da2717817ae569fbc99b","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"fd137bf8149bc6460f9b7b1fc292025da04cb9ee","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"8c1882dfee8f404d118020664b73eb4592172226","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"9b110a9dcecc59516c77cb3c0caf1f492f75df2d","versionType":"git"},{"version":"a42aa926843acca96c0dfbde2e835b8137f2f092","status":"affected","versionType":"git"},{"version":"9cb6c40a6ebe4a0cfc9d6a181958211682cffea9","status":"affected","versionType":"git"},{"version":"fbeb492694ce0441053de57699e1e2b7bc148a69","status":"affected","versionType":"git"},{"version":"0f6947f5f5208f6ebd4d76a82a4757e2839a23f8","status":"affected","versionType":"git"},{"version":"0090c13cbbdffd7da079ac56f80373a9a1be0bf8","status":"affected","versionType":"git"},{"version":"1bbf82d9f961414d6c76a08f7f843ea068e0ab7b","status":"affected","versionType":"git"},{"version":"5.15.32","status":"affected","lessThan":"5.15.222","versionType":"semver"},{"version":"4.14.279","status":"affected","lessThan":"4.15","versionType":"semver"},{"version":"4.19.243","status":"affected","lessThan":"4.20","versionType":"semver"},{"version":"5.4.193","status":"affected","lessThan":"5.5","versionType":"semver"},{"version":"5.10.109","status":"affected","lessThan":"5.11","versionType":"semver"},{"version":"5.16.18","status":"affected","lessThan":"5.17","versionType":"semver"},{"version":"5.17.1","status":"affected","lessThan":"5.18","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/core/pcm_native.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"5.15.222","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/core/pcm_native.c"]}],"references":["https://git.kernel.org/stable/c/e6cdd2a0470d64073349a970dc1691433804b271","https://git.kernel.org/stable/c/9857a75714bb5df4781e4d8b1a1753b1e17bf07a","https://git.kernel.org/stable/c/cbadf2575d25e7dcc0d4da2717817ae569fbc99b","https://git.kernel.org/stable/c/cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5","https://git.kernel.org/stable/c/fd137bf8149bc6460f9b7b1fc292025da04cb9ee","https://git.kernel.org/stable/c/8c1882dfee8f404d118020664b73eb4592172226","https://git.kernel.org/stable/c/9b110a9dcecc59516c77cb3c0caf1f492f75df2d"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98116.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98116","state":"PUBLISHED","datePublished":"2026-09-25T10:36:01.723Z","dateUpdated":"2026-10-19T09:14:08.504Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.317Z"},"containers":{"cna":{"title":"ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF\n\nsnd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation\nwith an mmap_count check performed under the PCM stream lock, but the\nlock is released long before the buffer is actually freed:\nsnd_pcm_sync_stop(), constraint refinement and do_free_pages() all\nhappen in between.  snd_pcm_mmap_data(), on the other hand, takes no\nlock at all: it validates against the old buffer's state and\ndma_bytes, remaps its pages into the VMA, and only then increments\nmmap_count.\n\nA concurrent mmap() can therefore slip in between the check and the\nfree.  remap_pfn_range() installs writable PTEs for the old buffer's\npages without taking page references, and the subsequent\ndo_free_pages() returns those pages to the page allocator while the\nVMA still maps them.  This leaves a stale, writable mapping of freed\npages: a page-level use-after-free that can be leveraged for local\nprivilege escalation.\n\nMake snd_pcm_mmap_data() participate in the buffer-access scheme\nintroduced for hw_params/hw_free: acquire runtime->buffer_accessing\nbefore validating and remapping, and release it afterwards.  Buffer\nreallocation already fails with -EBUSY while accessors are active,\nand the mmap side now fails with -EBUSY while a reallocation is in\nprogress, so the validate/remap sequence and the check/free sequence\ncan no longer interleave.\n\nA reproducer that turns this race into a stale writable mapping of\nthe freed DMA buffer pages is available on request."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"33061d0fba51d2bf70a2ef9645f703c33fe8e438","status":"affected","lessThan":"e6cdd2a0470d64073349a970dc1691433804b271","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"9857a75714bb5df4781e4d8b1a1753b1e17bf07a","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"cbadf2575d25e7dcc0d4da2717817ae569fbc99b","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"fd137bf8149bc6460f9b7b1fc292025da04cb9ee","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"8c1882dfee8f404d118020664b73eb4592172226","versionType":"git"},{"version":"92ee3c60ec9fe64404dc035e7c41277d74aa26cb","status":"affected","lessThan":"9b110a9dcecc59516c77cb3c0caf1f492f75df2d","versionType":"git"},{"version":"a42aa926843acca96c0dfbde2e835b8137f2f092","status":"affected","versionType":"git"},{"version":"9cb6c40a6ebe4a0cfc9d6a181958211682cffea9","status":"affected","versionType":"git"},{"version":"fbeb492694ce0441053de57699e1e2b7bc148a69","status":"affected","versionType":"git"},{"version":"0f6947f5f5208f6ebd4d76a82a4757e2839a23f8","status":"affected","versionType":"git"},{"version":"0090c13cbbdffd7da079ac56f80373a9a1be0bf8","status":"affected","versionType":"git"},{"version":"1bbf82d9f961414d6c76a08f7f843ea068e0ab7b","status":"affected","versionType":"git"},{"version":"5.15.32","status":"affected","lessThan":"5.15.222","versionType":"semver"},{"version":"4.14.279","status":"affected","lessThan":"4.15","versionType":"semver"},{"version":"4.19.243","status":"affected","lessThan":"4.20","versionType":"semver"},{"version":"5.4.193","status":"affected","lessThan":"5.5","versionType":"semver"},{"version":"5.10.109","status":"affected","lessThan":"5.11","versionType":"semver"},{"version":"5.16.18","status":"affected","lessThan":"5.17","versionType":"semver"},{"version":"5.17.1","status":"affected","lessThan":"5.18","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/core/pcm_native.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"5.15.222","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/core/pcm_native.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e6cdd2a0470d64073349a970dc1691433804b271"},{"url":"https://git.kernel.org/stable/c/9857a75714bb5df4781e4d8b1a1753b1e17bf07a"},{"url":"https://git.kernel.org/stable/c/cbadf2575d25e7dcc0d4da2717817ae569fbc99b"},{"url":"https://git.kernel.org/stable/c/cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5"},{"url":"https://git.kernel.org/stable/c/fd137bf8149bc6460f9b7b1fc292025da04cb9ee"},{"url":"https://git.kernel.org/stable/c/8c1882dfee8f404d118020664b73eb4592172226"},{"url":"https://git.kernel.org/stable/c/9b110a9dcecc59516c77cb3c0caf1f492f75df2d"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is triggered by mmap() on a local /dev/snd/pcmC*D* file descriptor (snd_pcm_mmap -> snd_pcm_mmap_data) racing with SNDRV_PCM_IOCTL_HW_PARAMS/HW_FREE ioctls on the same fd. No remote protocol carries any of the inputs.\nAC:L - One process controls both sides of the race: one thread calls mmap() and another calls hw_free/hw_params. The window runs from the mmap_count check under the stream lock through snd_pcm_sync_stop and refinement to do_free_pages, and the attacker can retry as often as needed.\nPR:L - Opening the PCM device node takes ordinary local user access, either the audio group or the udev uaccess ACL given to the logged-in seat user. No capability is checked on the mmap or hw_params/hw_free paths.\nUI:N - The attacker opens the device, sets hw_params and races the mmap against hw_free entirely through their own syscalls. No other user has to do anything.\nS:U - This is a local kernel privilege escalation within the same kernel security authority. It crosses no VM or IOMMU boundary.\nC:H - remap_pfn_range installs PTEs for the old DMA buffer pages without taking page references, and do_free_pages then frees them. The attacker keeps a direct mapping of whatever the page allocator reuses those pages for, such as page tables, cred or slab pages, and can read it.\nI:H - The stale mapping of the freed buffer pages is writable, which gives direct write access to reallocated kernel pages. This is a page-level UAF that enables privilege escalation, as the fix commit itself states.\nA:H - Writing through the stale PTEs into pages that have been reallocated corrupts arbitrary kernel memory, which leads to oopses, panics or page-state BUGs."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:14:08.504Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.32","versionEndExcluding":"5.15.222"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"7.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14.279"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.19.243"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.193"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.109"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16.18"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}