From: Jeongjun Park <aha310510@gmail.com> mainline inclusion from mainline-v6.16-rc1 commit d66adabe91803ef34a8b90613c81267b5ded1472 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/ICCDPO Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- syzbot reported that it discovered a use-after-free vulnerability, [0] [0]: https://lore.kernel.org/all/67af13f8.050a0220.21dd3.0038.GAE@google.com/ idr_for_each() is protected by rwsem, but this is not enough. If it is not protected by RCU read-critical region, when idr_for_each() calls radix_tree_node_free() through call_rcu() to free the radix_tree_node structure, the node will be freed immediately, and when reading the next node in radix_tree_for_each_slot(), the already freed memory may be read. Therefore, we need to add code to make sure that idr_for_each() is protected within the RCU read-critical region when we call it in shm_destroy_orphaned(). Link: https://lkml.kernel.org/r/20250424143322.18830-1-aha310510@gmail.com Fixes: b34a6b1da371 ("ipc: introduce shm_rmid_forced sysctl") Signed-off-by: Jeongjun Park <aha310510@gmail.com> Reported-by: syzbot+a2b84e569d06ca3a949c@syzkaller.appspotmail.com Cc: Jeongjun Park <aha310510@gmail.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Vasiliy Kulikov <segoon@openwall.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Wang Tao <wangtao554@huawei.com> --- ipc/shm.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/ipc/shm.c b/ipc/shm.c index b418731d66e8..323a5810a947 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -417,8 +417,11 @@ static int shm_try_destroy_orphaned(int id, void *p, void *data) void shm_destroy_orphaned(struct ipc_namespace *ns) { down_write(&shm_ids(ns).rwsem); - if (shm_ids(ns).in_use) + if (shm_ids(ns).in_use) { + rcu_read_lock(); idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns); + rcu_read_unlock(); + } up_write(&shm_ids(ns).rwsem); } -- 2.34.1