CVE-2026-98116

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.

• linux linux kernel (>= 4.14.279 < 4.15) • linux linux kernel (>= 4.19.243 < 4.20) • linux linux kernel (>= 5.4.193 < 5.5) • linux linux kernel (>= 5.10.109 < 5.11) • linux linux kernel (>= 5.15.32 < 5.15.222) • linux linux kernel (>= 5.16.18 <= 5.17.1) • linux linux kernel (>= 6.7 < 6.12.111) • linux linux kernel (>= 6.13 < 6.18.53) • linux linux kernel (>= 6.19 < 7.2.7) • linux linux kernel 7.3