From: Lee Jia Jie Date: Thu, 9 Jul 2026 13:56:19 +0000 (+0800) Subject: perf/aux: Fix page UAF in map_range() X-Git-Tag: v7.2-rc3~12^2~2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5948aaf64f81f217a25dcc2bf6c0779bca19566c;p=thirdparty%2Fkernel%2Flinux.git perf/aux: Fix page UAF in map_range() map_range() reads rb->aux_pages[], rb->aux_nr_pages and rb->aux_pgoff via perf_mmap_to_page() while holding only event->mmap_mutex. Those fields are serialized by rb->aux_mutex, and mmap_mutex is per event. Thus, two events sharing one rb via PERF_EVENT_IOC_SET_OUTPUT can race rb_alloc_aux() with map_range(), leading to a page-UAF scenario as follows: CPU 0 CPU 1 ===== ===== rb_alloc_aux() map_range() [1]: allocate rb->aux_pages[0] [2]: rb->aux_nr_pages++ [3]: perf_mmap_to_page() returns rb->aux_pages[0] [4]: map it as VM_PFNMAP [5]: rb->aux_pgoff = 1 munmap the page [6]: free rb->aux_pages[0] Pages mapped as VM_PFNMAP have no refcount protection, so CPU 1 holds a mapping to a freed physical frame. Fix this by taking rb->aux_mutex across the page walk in map_range(). Fixes: b709eb872e19 ("perf: map pages in advance") Signed-off-by: Lee Jia Jie Signed-off-by: Ingo Molnar Cc: stable@vger.kernel.org Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Namhyung Kim --- diff --git a/kernel/events/core.c b/kernel/events/core.c index d7f3e2c2ecb1..ba5bd6a78fe7 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7150,6 +7150,8 @@ static int map_range(struct perf_buffer *rb, struct vm_area_struct *vma) int err = 0; unsigned long pagenum; + guard(mutex)(&rb->aux_mutex); + /* * We map this as a VM_PFNMAP VMA. *