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af_unix: annote lockless accesses to unix_tot_inflight & gc_in_progress
wait_for_unix_gc() reads unix_tot_inflight & gc_in_progress
without synchronization.
Adds READ_ONCE()/WRITE_ONCE() and their associated comments
to better document the intent.
BUG: KCSAN: data-race in unix_inflight / wait_for_unix_gc
write to 0xffffffff86e2b7c0 of 4 bytes by task 9380 on cpu 0:
unix_inflight+0x1e8/0x260 net/unix/scm.c:63
unix_attach_fds+0x10c/0x1e0 net/unix/scm.c:121
unix_scm_to_skb net/unix/af_unix.c:1674 [inline]
unix_dgram_sendmsg+0x679/0x16b0 net/unix/af_unix.c:1817
unix_seqpacket_sendmsg+0xcc/0x110 net/unix/af_unix.c:2258
sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg net/socket.c:724 [inline]
____sys_sendmsg+0x39a/0x510 net/socket.c:2409
___sys_sendmsg net/socket.c:2463 [inline]
__sys_sendmmsg+0x267/0x4c0 net/socket.c:2549
__do_sys_sendmmsg net/socket.c:2578 [inline]
__se_sys_sendmmsg net/socket.c:2575 [inline]
__x64_sys_sendmmsg+0x53/0x60 net/socket.c:2575
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 0xffffffff86e2b7c0 of 4 bytes by task 9375 on cpu 1:
wait_for_unix_gc+0x24/0x160 net/unix/garbage.c:196
unix_dgram_sendmsg+0x8e/0x16b0 net/unix/af_unix.c:1772
unix_seqpacket_sendmsg+0xcc/0x110 net/unix/af_unix.c:2258
sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg net/socket.c:724 [inline]
____sys_sendmsg+0x39a/0x510 net/socket.c:2409
___sys_sendmsg net/socket.c:2463 [inline]
__sys_sendmmsg+0x267/0x4c0 net/socket.c:2549
__do_sys_sendmmsg net/socket.c:2578 [inline]
__se_sys_sendmmsg net/socket.c:2575 [inline]
__x64_sys_sendmmsg+0x53/0x60 net/socket.c:2575
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: 0x00000002 -> 0x00000004
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9375 Comm: syz-executor.1 Not tainted 5.16.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Fixes: 9915672d41
("af_unix: limit unix_tot_inflight")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Link: https://lore.kernel.org/r/20220114164328.2038499-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
parent
d90d0c175c
commit
9d6d7f1cb6
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@ -192,8 +192,11 @@ void wait_for_unix_gc(void)
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{
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/* If number of inflight sockets is insane,
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* force a garbage collect right now.
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* Paired with the WRITE_ONCE() in unix_inflight(),
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* unix_notinflight() and gc_in_progress().
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*/
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if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress)
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if (READ_ONCE(unix_tot_inflight) > UNIX_INFLIGHT_TRIGGER_GC &&
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!READ_ONCE(gc_in_progress))
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unix_gc();
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wait_event(unix_gc_wait, gc_in_progress == false);
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}
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@ -213,7 +216,9 @@ void unix_gc(void)
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if (gc_in_progress)
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goto out;
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gc_in_progress = true;
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/* Paired with READ_ONCE() in wait_for_unix_gc(). */
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WRITE_ONCE(gc_in_progress, true);
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/* First, select candidates for garbage collection. Only
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* in-flight sockets are considered, and from those only ones
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* which don't have any external reference.
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@ -299,7 +304,10 @@ void unix_gc(void)
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/* All candidates should have been detached by now. */
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BUG_ON(!list_empty(&gc_candidates));
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gc_in_progress = false;
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/* Paired with READ_ONCE() in wait_for_unix_gc(). */
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WRITE_ONCE(gc_in_progress, false);
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wake_up(&unix_gc_wait);
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out:
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@ -60,7 +60,8 @@ void unix_inflight(struct user_struct *user, struct file *fp)
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} else {
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BUG_ON(list_empty(&u->link));
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}
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unix_tot_inflight++;
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/* Paired with READ_ONCE() in wait_for_unix_gc() */
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WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
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}
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user->unix_inflight++;
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spin_unlock(&unix_gc_lock);
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@ -80,7 +81,8 @@ void unix_notinflight(struct user_struct *user, struct file *fp)
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if (atomic_long_dec_and_test(&u->inflight))
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list_del_init(&u->link);
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unix_tot_inflight--;
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/* Paired with READ_ONCE() in wait_for_unix_gc() */
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WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
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}
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user->unix_inflight--;
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spin_unlock(&unix_gc_lock);
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