From: Lance Yang <lance.yang@linux.dev> stable inclusion from stable-v6.6.117 commit 42d486d35a4143cc37fc72ee66edc99d942dd367 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/11252 CVE: CVE-2025-40272 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 6f86d0534fddfbd08687fa0f01479d4226bc3c3d upstream. When a page fault occurs in a secret memory file created with `memfd_secret(2)`, the kernel will allocate a new folio for it, mark the underlying page as not-present in the direct map, and add it to the file mapping. If two tasks cause a fault in the same page concurrently, both could end up allocating a folio and removing the page from the direct map, but only one would succeed in adding the folio to the file mapping. The task that failed undoes the effects of its attempt by (a) freeing the folio again and (b) putting the page back into the direct map. However, by doing these two operations in this order, the page becomes available to the allocator again before it is placed back in the direct mapping. If another task attempts to allocate the page between (a) and (b), and the kernel tries to access it via the direct map, it would result in a supervisor not-present page fault. Fix the ordering to restore the direct map before the folio is freed. Link: https://lkml.kernel.org/r/20251031120955.92116-1-lance.yang@linux.dev Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas") Signed-off-by: Lance Yang <lance.yang@linux.dev> Reported-by: Google Big Sleep <big-sleep-vuln-reports@google.com> Closes: https://lore.kernel.org/linux-mm/CAEXGt5QeDpiHTu3K9tvjUTPqo+d-=wuCNYPa+6sWKr... Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Wang Hai <wanghai38@huawei.com> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- mm/secretmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/secretmem.c b/mm/secretmem.c index 88fbd3598207..987def80d810 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c @@ -84,13 +84,13 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf) __folio_mark_uptodate(folio); err = filemap_add_folio(mapping, folio, offset, gfp); if (unlikely(err)) { - folio_put(folio); /* * If a split of large page was required, it * already happened when we marked the page invalid * which guarantees that this call won't fail */ set_direct_map_default_noflush(page); + folio_put(folio); if (err == -EEXIST) goto retry; -- 2.43.0