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Message-ID: <20250331091532.224982-1-edumazet@google.com>
Date: Mon, 31 Mar 2025 09:15:32 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot+fae49d997eb56fa7c74d@...kaller.appspotmail.com,
Marcelo Ricardo Leitner <marcelo.leitner@...il.com>, Xin Long <lucien.xin@...il.com>
Subject: [PATCH net] sctp: add mutual exclusion in proc_sctp_do_udp_port()
We must serialize calls to sctp_udp_sock_stop() and sctp_udp_sock_start()
or risk a crash as syzbot reported:
Oops: general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 1 UID: 0 PID: 6551 Comm: syz.1.44 Not tainted 6.14.0-syzkaller-g7f2ff7b62617 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:kernel_sock_shutdown+0x47/0x70 net/socket.c:3653
Call Trace:
<TASK>
udp_tunnel_sock_release+0x68/0x80 net/ipv4/udp_tunnel_core.c:181
sctp_udp_sock_stop+0x71/0x160 net/sctp/protocol.c:930
proc_sctp_do_udp_port+0x264/0x450 net/sctp/sysctl.c:553
proc_sys_call_handler+0x3d0/0x5b0 fs/proc/proc_sysctl.c:601
iter_file_splice_write+0x91c/0x1150 fs/splice.c:738
do_splice_from fs/splice.c:935 [inline]
direct_splice_actor+0x18f/0x6c0 fs/splice.c:1158
splice_direct_to_actor+0x342/0xa30 fs/splice.c:1102
do_splice_direct_actor fs/splice.c:1201 [inline]
do_splice_direct+0x174/0x240 fs/splice.c:1227
do_sendfile+0xafd/0xe50 fs/read_write.c:1368
__do_sys_sendfile64 fs/read_write.c:1429 [inline]
__se_sys_sendfile64 fs/read_write.c:1415 [inline]
__x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1415
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
Fixes: 046c052b475e ("sctp: enable udp tunneling socks")
Reported-by: syzbot+fae49d997eb56fa7c74d@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/67ea5c01.050a0220.1547ec.012b.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc: Xin Long <lucien.xin@...il.com>
---
net/sctp/sysctl.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 8e1e97be4df79f3245e2bbbeb0a75841abc67f58..ee3eac338a9deef064f273e29bb59b057835d3f1 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -525,6 +525,8 @@ static int proc_sctp_do_auth(const struct ctl_table *ctl, int write,
return ret;
}
+static DEFINE_MUTEX(sctp_sysctl_mutex);
+
static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
@@ -549,6 +551,7 @@ static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write,
if (new_value > max || new_value < min)
return -EINVAL;
+ mutex_lock(&sctp_sysctl_mutex);
net->sctp.udp_port = new_value;
sctp_udp_sock_stop(net);
if (new_value) {
@@ -561,6 +564,7 @@ static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write,
lock_sock(sk);
sctp_sk(sk)->udp_port = htons(net->sctp.udp_port);
release_sock(sk);
+ mutex_unlock(&sctp_sysctl_mutex);
}
return ret;
--
2.49.0.472.ge94155a9ec-goog
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