Description (CNA)
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 (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 33061d0fba51d2bf70a2ef9645f703c33fe8e438 before e6cdd2a0470d64073349a970dc1691433804b271; affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before 9857a75714bb5df4781e4d8b1a1753b1e17bf07a; affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before cbadf2575d25e7dcc0d4da2717817ae569fbc99b; affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5; affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before fd137bf8149bc6460f9b7b1fc292025da04cb9ee; affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before 8c1882dfee8f404d118020664b73eb4592172226; affected 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before 9b110a9dcecc59516c77cb3c0caf1f492f75df2d; affected a42aa926843acca96c0dfbde2e835b8137f2f092; affected 9cb6c40a6ebe4a0cfc9d6a181958211682cffea9; affected fbeb492694ce0441053de57699e1e2b7bc148a69; affected 0f6947f5f5208f6ebd4d76a82a4757e2839a23f8; affected 0090c13cbbdffd7da079ac56f80373a9a1be0bf8; affected 1bbf82d9f961414d6c76a08f7f843ea068e0ab7b; affected 5.15.32 before 5.15.222; affected 4.14.279 before 4.15; affected 4.19.243 before 4.20; affected 5.4.193 before 5.5; affected 5.10.109 before 5.11; affected 5.16.18 before 5.17; affected 5.17.1 before 5.18 |
| Linux / Linux | affected 5.18; unaffected 0 before 5.18; unaffected 5.15.222 through 5.15.*; unaffected 6.1.189 through 6.1.*; unaffected 6.6.158 through 6.6.*; unaffected 6.12.111 through 6.12.*; unaffected 6.18.53 through 6.18.*; unaffected 7.2.7 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.
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