From: Kuniyuki Iwashima <kuniyu@amazon.co.jp> stable inclusion from stable-v5.15.46 commit 5d5d993f16be15d124be7b8ec71b28ef7b7dc3af category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBP6RN CVE: CVE-2022-49443 Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... -------------------------------- [ Upstream commit d679ae94fdd5d3ab00c35078f5af5f37e068b03d ] ep_poll() first calls ep_events_available() with no lock held and checks if ep->rdllist is empty by list_empty_careful(), which reads rdllist->prev. Thus all accesses to it need some protection to avoid store/load-tearing. Note INIT_LIST_HEAD_RCU() already has the annotation for both prev and next. Commit bf3b9f6372c4 ("epoll: Add busy poll support to epoll with socket fds.") added the first lockless ep_events_available(), and commit c5a282e9635e ("fs/epoll: reduce the scope of wq lock in epoll_wait()") made some ep_events_available() calls lockless and added single call under a lock, finally commit e59d3c64cba6 ("epoll: eliminate unnecessary lock for zero timeout") made the last ep_events_available() lockless. BUG: KCSAN: data-race in do_epoll_wait / do_epoll_wait write to 0xffff88810480c7d8 of 8 bytes by task 1802 on cpu 0: INIT_LIST_HEAD include/linux/list.h:38 [inline] list_splice_init include/linux/list.h:492 [inline] ep_start_scan fs/eventpoll.c:622 [inline] ep_send_events fs/eventpoll.c:1656 [inline] ep_poll fs/eventpoll.c:1806 [inline] do_epoll_wait+0x4eb/0xf40 fs/eventpoll.c:2234 do_epoll_pwait fs/eventpoll.c:2268 [inline] __do_sys_epoll_pwait fs/eventpoll.c:2281 [inline] __se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2275 __x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2275 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff88810480c7d8 of 8 bytes by task 1799 on cpu 1: list_empty_careful include/linux/list.h:329 [inline] ep_events_available fs/eventpoll.c:381 [inline] ep_poll fs/eventpoll.c:1797 [inline] do_epoll_wait+0x279/0xf40 fs/eventpoll.c:2234 do_epoll_pwait fs/eventpoll.c:2268 [inline] __do_sys_epoll_pwait fs/eventpoll.c:2281 [inline] __se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2275 __x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2275 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0xffff88810480c7d0 -> 0xffff888103c15098 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 1799 Comm: syz-fuzzer Tainted: G W 5.17.0-rc7-syzkaller-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Link: https://lkml.kernel.org/r/20220322002653.33865-3-kuniyu@amazon.co.jp Fixes: e59d3c64cba6 ("epoll: eliminate unnecessary lock for zero timeout") Fixes: c5a282e9635e ("fs/epoll: reduce the scope of wq lock in epoll_wait()") Fixes: bf3b9f6372c4 ("epoll: Add busy poll support to epoll with socket fds.") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp> Reported-by: syzbot+bdd6e38a1ed5ee58d8bd@syzkaller.appspotmail.com Cc: Al Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org> Cc: Kuniyuki Iwashima <kuniyu@amazon.co.jp> Cc: Kuniyuki Iwashima <kuni1840@gmail.com> Cc: "Soheil Hassas Yeganeh" <soheil@google.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Sridhar Samudrala" <sridhar.samudrala@intel.com> Cc: Alexander Duyck <alexander.h.duyck@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: include/linux/list.h [This patch lacks the prerequisite patch for the list_is_head(). Therefore, only keep the current version of "next == head" as is and only modify the READ_ONCE() additions introduced by this patch.] Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- include/linux/list.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/list.h b/include/linux/list.h index fa9f691f2553..aab9705902ed 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -33,7 +33,7 @@ static inline void INIT_LIST_HEAD(struct list_head *list) { WRITE_ONCE(list->next, list); - list->prev = list; + WRITE_ONCE(list->prev, list); } #ifdef CONFIG_DEBUG_LIST @@ -296,7 +296,7 @@ static inline int list_empty(const struct list_head *head) static inline void list_del_init_careful(struct list_head *entry) { __list_del_entry(entry); - entry->prev = entry; + WRITE_ONCE(entry->prev, entry); smp_store_release(&entry->next, entry); } @@ -316,7 +316,7 @@ static inline void list_del_init_careful(struct list_head *entry) static inline int list_empty_careful(const struct list_head *head) { struct list_head *next = smp_load_acquire(&head->next); - return (next == head) && (next == head->prev); + return (next == head) && (next == READ_ONCE(head->prev)); } /** -- 2.34.1