From: Yilin Zhu <zylzyl2333@gmail.com> stable inclusion from stable-v5.10.259 commit b1e9aef48e4d8a0c1b54fb913077b0824ed7d650 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/15634 CVE: CVE-2026-52930 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 2e5c6f4fd4001562781e99bbfc7f1f0127187542 upstream. shm_destroy_orphaned() walks the shm idr under shm_ids(ns).rwsem, but that does not serialize all fields tested by shm_may_destroy(). In particular, shm_nattch is updated while holding shm_perm.lock, and attach paths can do that without holding the rwsem. Do not decide that an orphaned segment is unused before taking the object lock. Move the shm_may_destroy() check under shm_perm.lock, matching the other destroy paths, and unlock the segment when it no longer qualifies for removal. Link: https://lore.kernel.org/9d97cc1031de2d0bace0edf3a668818aa2f4eca6.1777410234.... Fixes: 4c677e2eefdb ("shm: optimize locking and ipc_namespace getting") Reported-by: Yuan Tan <yuantan098@gmail.com> Reported-by: Yifan Wu <yifanwucs@gmail.com> Reported-by: Juefei Pu <tomapufckgml@gmail.com> Reported-by: Xin Liu <bird@lzu.edu.cn> Signed-off-by: Yilin Zhu <zylzyl2333@gmail.com> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn> Cc: Christian Brauner <brauner@kernel.org> Cc: Jeongjun Park <aha310510@gmail.com> Cc: Kees Cook <kees@kernel.org> Cc: Liam Howlett <liam@infradead.org> Cc: Lorenzo Stoakes <ljs@kernel.org> Cc: Serge Hallyn <sergeh@kernel.org> Cc: Vasiliy Kulikov <segoon@openwall.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Fanhua Li <lifanhua5@huawei.com> --- ipc/shm.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index bb017dd760f4d..25190965c9a50 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -415,15 +415,17 @@ static int shm_try_destroy_orphaned(int id, void *p, void *data) * We want to destroy segments without users and with already * exit'ed originating process. * - * As shp->* are changed under rwsem, it's safe to skip shp locking. + * shm_nattch can be changed under shm_perm.lock without holding the + * rwsem, so take the object lock before checking shm_may_destroy(). */ if (!list_empty(&shp->shm_clist)) return 0; - if (shm_may_destroy(shp)) { - shm_lock_by_ptr(shp); + shm_lock_by_ptr(shp); + if (shm_may_destroy(shp)) shm_destroy(ns, shp); - } + else + shm_unlock(shp); return 0; } -- 2.43.0