diff mbox

[net-next] tcp: fix null ptr deref in getsockopt(..., TCP_ULP, ...)

Message ID 20170626153647.GA15170@achao-mbp1.DHCP.thefacebook.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Dave Watson June 26, 2017, 3:36 p.m. UTC 
If icsk_ulp_ops is unset, it dereferences a null ptr.
Add a null ptr check.

BUG: KASAN: null-ptr-deref in copy_to_user include/linux/uaccess.h:168 [inline]
BUG: KASAN: null-ptr-deref in do_tcp_getsockopt.isra.33+0x24f/0x1e30 net/ipv4/tcp.c:3057
Read of size 4 at addr 0000000000000020 by task syz-executor1/15452

Signed-off-by: Dave Watson <davejwatson@fb.com>
Reported-by: "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com>
---
 net/ipv4/tcp.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

David Miller June 27, 2017, 7:39 p.m. UTC | #1 
From: Dave Watson <davejwatson@fb.com>
Date: Mon, 26 Jun 2017 08:36:47 -0700

> If icsk_ulp_ops is unset, it dereferences a null ptr.
> Add a null ptr check.
> 
> BUG: KASAN: null-ptr-deref in copy_to_user include/linux/uaccess.h:168 [inline]
> BUG: KASAN: null-ptr-deref in do_tcp_getsockopt.isra.33+0x24f/0x1e30 net/ipv4/tcp.c:3057
> Read of size 4 at addr 0000000000000020 by task syz-executor1/15452
> 
> Signed-off-by: Dave Watson <davejwatson@fb.com>
> Reported-by: "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com>

Applied, thanks.
diff mbox

Patch

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 058f509..4c88d20 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3062,6 +3062,11 @@  static int do_tcp_getsockopt(struct sock *sk, int level,
 		if (get_user(len, optlen))
 			return -EFAULT;
 		len = min_t(unsigned int, len, TCP_ULP_NAME_MAX);
+		if (!icsk->icsk_ulp_ops) {
+			if (put_user(0, optlen))
+				return -EFAULT;
+			return 0;
+		}
 		if (put_user(len, optlen))
 			return -EFAULT;
 		if (copy_to_user(optval, icsk->icsk_ulp_ops->name, len))