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authorEric Dumazet <edumazet@google.com>2022-01-14 08:43:28 -0800
committerJakub Kicinski <kuba@kernel.org>2022-01-14 18:31:37 -0800
commit9d6d7f1cb67cdee15f1a0e85aacfb924e0e02435 (patch)
tree34a06c72834b8513c7830347dc5f71c29754fe14 /net/unix
parentd90d0c175cf2982789d336dda928c0f69d3e8a9d (diff)
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: 9915672d4127 ("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>
Diffstat (limited to 'net/unix')
-rw-r--r--net/unix/garbage.c14
-rw-r--r--net/unix/scm.c6
2 files changed, 15 insertions, 5 deletions
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 12e2ddaf887f..d45d5366115a 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -192,8 +192,11 @@ void wait_for_unix_gc(void)
{
/* If number of inflight sockets is insane,
* force a garbage collect right now.
+ * Paired with the WRITE_ONCE() in unix_inflight(),
+ * unix_notinflight() and gc_in_progress().
*/
- if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress)
+ if (READ_ONCE(unix_tot_inflight) > UNIX_INFLIGHT_TRIGGER_GC &&
+ !READ_ONCE(gc_in_progress))
unix_gc();
wait_event(unix_gc_wait, gc_in_progress == false);
}
@@ -213,7 +216,9 @@ void unix_gc(void)
if (gc_in_progress)
goto out;
- gc_in_progress = true;
+ /* Paired with READ_ONCE() in wait_for_unix_gc(). */
+ WRITE_ONCE(gc_in_progress, true);
+
/* First, select candidates for garbage collection. Only
* in-flight sockets are considered, and from those only ones
* which don't have any external reference.
@@ -299,7 +304,10 @@ void unix_gc(void)
/* All candidates should have been detached by now. */
BUG_ON(!list_empty(&gc_candidates));
- gc_in_progress = false;
+
+ /* Paired with READ_ONCE() in wait_for_unix_gc(). */
+ WRITE_ONCE(gc_in_progress, false);
+
wake_up(&unix_gc_wait);
out:
diff --git a/net/unix/scm.c b/net/unix/scm.c
index 052ae709ce28..aa27a02478dc 100644
--- a/net/unix/scm.c
+++ b/net/unix/scm.c
@@ -60,7 +60,8 @@ void unix_inflight(struct user_struct *user, struct file *fp)
} else {
BUG_ON(list_empty(&u->link));
}
- unix_tot_inflight++;
+ /* Paired with READ_ONCE() in wait_for_unix_gc() */
+ WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
}
user->unix_inflight++;
spin_unlock(&unix_gc_lock);
@@ -80,7 +81,8 @@ void unix_notinflight(struct user_struct *user, struct file *fp)
if (atomic_long_dec_and_test(&u->inflight))
list_del_init(&u->link);
- unix_tot_inflight--;
+ /* Paired with READ_ONCE() in wait_for_unix_gc() */
+ WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
}
user->unix_inflight--;
spin_unlock(&unix_gc_lock);