On 21/06/2021 16:56, Pavel Skripkin wrote:
On Sun, 20 Jun 2021 16:22:16 -0700
syzbot <syzbot+5dda108b672b54141857@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Hello,
syzbot found the following issue on:
HEAD commit: 0c337952 Merge tag 'wireless-drivers-next-2021-06-16'
of g.. git tree: net-next
console output:
https://syzkaller.appspot.com/x/log.txt?x=1621de10300000 kernel
config: https://syzkaller.appspot.com/x/.config?x=a6380da8984033f1
dashboard link:
https://syzkaller.appspot.com/bug?extid=5dda108b672b54141857 syz
repro:
https://syzkaller.appspot.com/x/repro.syz?x=121d2d20300000 C
reproducer: https://syzkaller.appspot.com/x/repro.c?x=100bd768300000
The issue was bisected to:
commit f9006acc8dfe59e25aa75729728ac57a8d84fc32
Author: Florian Westphal <fw@xxxxxxxxx>
Date: Wed Apr 21 07:51:08 2021 +0000
netfilter: arp_tables: pass table pointer via nf_hook_ops
I think, bisection is wrong this time :)
It should be e0e4b8fa533858532f1b9ea9c6a4660d09beb37a ("net/smc: Add SMC
statistics support")
Some debug results:
syzkaller repro just opens the socket and calls sendmsg. Ftrace log:
0) | smc_create() {
0) | smc_sock_alloc() {
0) + 88.493 us | smc_hash_sk();
0) ! 131.487 us | }
0) ! 189.912 us | }
0) | smc_sendmsg() {
0) 2.808 us | smc_tx_sendmsg();
0) ! 148.484 us | }
That means, that smc_buf_create() wasn't called at all, so we need to
check sndbuf_desc before dereferencing
Something like this should work
diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
index 075c4f4b4..e24071b12 100644
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -154,7 +154,7 @@ int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len)
goto out_err;
}
- if (len > conn->sndbuf_desc->len)
+ if (conn->sndbuf_desc && len > conn->sndbuf_desc->len)
SMC_STAT_RMB_TX_SIZE_SMALL(smc, !conn->lnk);
if (len > conn->peer_rmbe_size)
Thoughts?
+CC Guvenc Gulce
With regards,
Pavel Skripkin
Thanks for analyzing the cause. Your approach would work but I would prefer that we
check the state of the socket before doing the statistics relevant if check. This will ensure
that smc_buf_create() was already called.
I am testing the fix at the moment which would look like the following:
diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
index 075c4f4b41cf..289025cd545a 100644
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -154,6 +154,9 @@ int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len)
goto out_err;
}
+ if (sk->sk_state == SMC_INIT)
+ return -ENOTCONN;
+
if (len > conn->sndbuf_desc->len)
SMC_STAT_RMB_TX_SIZE_SMALL(smc, !conn->lnk);
