Commit 7f404029 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Zicheng Qu
Browse files

list: fix a data-race around ep->rdllist 

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/commit/?id=5d5d993f16be15d124be7b8ec71b28ef7b7dc3af

--------------------------------

[ Upstream commit d679ae94 ]

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 bf3b9f63 ("epoll: Add busy poll support to epoll with socket
fds.") added the first lockless ep_events_available(), and commit
c5a282e9 ("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 e59d3c64 ("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: e59d3c64 ("epoll: eliminate unnecessary lock for zero timeout")
Fixes: c5a282e9 ("fs/epoll: reduce the scope of wq lock in epoll_wait()")
Fixes: bf3b9f63 ("epoll: Add busy poll support to epoll with socket fds.")
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.co.jp>
Reported-by: default avatar <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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarSasha 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: default avatarZicheng Qu <quzicheng@huawei.com>
parent 8c45ad1b

include/linux/list.h

+3 −3
Original line number Diff line number Diff line
@@ -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));

}



/**