This is a note to let you know that I've just added the patch titled
af_unix: Fix data-races around user->unix_inflight.
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
af_unix-fix-data-races-around-user-unix_inflight.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0bdfc88ad5da504c2b44e08cd503b3ce35e602d2
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date: Fri Sep 1 17:27:05 2023 -0700
af_unix: Fix data-races around user->unix_inflight.
[ Upstream commit 0bc36c0650b21df36fbec8136add83936eaf0607 ]
user->unix_inflight is changed under spin_lock(unix_gc_lock),
but too_many_unix_fds() reads it locklessly.
Let's annotate the write/read accesses to user->unix_inflight.
BUG: KCSAN: data-race in unix_attach_fds / unix_inflight
write to 0xffffffff8546f2d0 of 8 bytes by task 44798 on cpu 1:
unix_inflight+0x157/0x180 net/unix/scm.c:66
unix_attach_fds+0x147/0x1e0 net/unix/scm.c:123
unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
sock_sendmsg_nosec net/socket.c:725 [inline]
sock_sendmsg+0x148/0x160 net/socket.c:748
____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
___sys_sendmsg+0xc6/0x140 net/socket.c:2548
__sys_sendmsg+0x94/0x140 net/socket.c:2577
__do_sys_sendmsg net/socket.c:2586 [inline]
__se_sys_sendmsg net/socket.c:2584 [inline]
__x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
read to 0xffffffff8546f2d0 of 8 bytes by task 44814 on cpu 0:
too_many_unix_fds net/unix/scm.c:101 [inline]
unix_attach_fds+0x54/0x1e0 net/unix/scm.c:110
unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
sock_sendmsg_nosec net/socket.c:725 [inline]
sock_sendmsg+0x148/0x160 net/socket.c:748
____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
___sys_sendmsg+0xc6/0x140 net/socket.c:2548
__sys_sendmsg+0x94/0x140 net/socket.c:2577
__do_sys_sendmsg net/socket.c:2586 [inline]
__se_sys_sendmsg net/socket.c:2584 [inline]
__x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
value changed: 0x000000000000000c -> 0x000000000000000d
Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 44814 Comm: systemd-coredum Not tainted 6.4.0-11989-g6843306689af #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Fixes: 712f4aad406b ("unix: properly account for FDs passed over unix sockets")
Reported-by: syzkaller <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Acked-by: Willy Tarreau <w@xxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/unix/scm.c b/net/unix/scm.c
index 6c10af6037e39..c4dde276fea56 100644
--- a/net/unix/scm.c
+++ b/net/unix/scm.c
@@ -60,7 +60,7 @@ void unix_inflight(struct user_struct *user, struct file *fp)
/* Paired with READ_ONCE() in wait_for_unix_gc() */
WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
}
- user->unix_inflight++;
+ WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
spin_unlock(&unix_gc_lock);
}
@@ -81,7 +81,7 @@ void unix_notinflight(struct user_struct *user, struct file *fp)
/* Paired with READ_ONCE() in wait_for_unix_gc() */
WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
}
- user->unix_inflight--;
+ WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
spin_unlock(&unix_gc_lock);
}
@@ -95,7 +95,7 @@ static inline bool too_many_unix_fds(struct task_struct *p)
{
struct user_struct *user = current_user();
- if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
+ if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE)))
return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
return false;
}
