blob: e7c976b39e55c58229dba94ffab643ce7ef5dbf5 [file] [log] [blame]
From 47a481532966d904cc890ef7163faf84898bb3aa Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 22 Jan 2020 09:07:35 -0800
Subject: [PATCH] tun: add mutex_unlock() call and napi.skb clearing in
tun_get_user()
commit 1efba987c48629c0c64703bb4ea76ca1a3771d17 upstream.
If both IFF_NAPI_FRAGS mode and XDP are enabled, and the XDP program
consumes the skb, we need to clear the napi.skb (or risk
a use-after-free) and release the mutex (or risk a deadlock)
WARNING: lock held when returning to user space!
5.5.0-rc6-syzkaller #0 Not tainted
------------------------------------------------
syz-executor.0/455 is leaving the kernel with locks still held!
1 lock held by syz-executor.0/455:
#0: ffff888098f6e748 (&tfile->napi_mutex){+.+.}, at: tun_get_user+0x1604/0x3fc0 drivers/net/tun.c:1835
Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Petar Penkov <ppenkov@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 34b0e1416525..bead09f37ebd 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1937,6 +1937,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
if (ret != XDP_PASS) {
rcu_read_unlock();
local_bh_enable();
+ if (frags) {
+ tfile->napi.skb = NULL;
+ mutex_unlock(&tfile->napi_mutex);
+ }
return total_len;
}
}
--
2.7.4