From 501e89d3aef10f9a5b79137fbb0bcd5bf9cac2ac Mon Sep 17 00:00:00 2001 From: Dave Jones Date: Tue, 1 Nov 2011 16:26:44 +0000 Subject: [PATCH] x25: Fix NULL dereference in x25_recvmsg commit cb101ed2 in 3.0 introduced a bug in x25_recvmsg() When passed bogus junk from userspace, x25->neighbour can be NULL, as shown in this oops.. BUG: unable to handle kernel NULL pointer dereference at 000000000000001c IP: [] x25_recvmsg+0x4d/0x280 [x25] PGD 1015f3067 PUD 105072067 PMD 0 Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC CPU 0 Pid: 27928, comm: iknowthis Not tainted 3.1.0+ #2 Gigabyte Technology Co., Ltd. GA-MA78GM-S2H/GA-MA78GM-S2H RIP: 0010:[] [] x25_recvmsg+0x4d/0x280 [x25] RSP: 0018:ffff88010c0b7cc8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffff88010c0b7d78 RCX: 0000000000000c02 RDX: ffff88010c0b7d78 RSI: ffff88011c93dc00 RDI: ffff880103f667b0 RBP: ffff88010c0b7d18 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff880103f667b0 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f479ce7f700(0000) GS:ffff88012a600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 000000000000001c CR3: 000000010529e000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process iknowthis (pid: 27928, threadinfo ffff88010c0b6000, task ffff880103faa4f0) Stack: 0000000000000c02 0000000000000c02 ffff88010c0b7d18 ffffff958153cb37 ffffffff8153cb60 0000000000000c02 ffff88011c93dc00 0000000000000000 0000000000000c02 ffff88010c0b7e10 ffff88010c0b7de8 ffffffff815372c2 Call Trace: [] ? sock_update_classid+0xb0/0x180 [] sock_aio_read.part.10+0x142/0x150 [] ? inode_has_perm+0x62/0xa0 [] sock_aio_read+0x2d/0x40 [] do_sync_read+0xd2/0x110 [] ? security_file_permission+0x96/0xb0 [] ? rw_verify_area+0x61/0x100 [] vfs_read+0x16d/0x180 [] sys_read+0x4d/0x90 [] system_call_fastpath+0x16/0x1b Code: 8b 66 20 4c 8b 32 48 89 d3 48 89 4d b8 45 89 c7 c7 45 cc 95 ff ff ff 4d 85 e4 0f 84 ed 01 00 00 49 8b 84 24 18 05 00 00 4c 89 e7 78 1c 01 45 19 ed 31 f6 e8 d5 37 ff e0 41 0f b6 44 24 0e 41 Signed-off-by: Dave Jones Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/x25/af_x25.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index 5f03e4ea65bf..3e16c6abde4f 100644 --- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -1261,14 +1261,19 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock, struct x25_sock *x25 = x25_sk(sk); struct sockaddr_x25 *sx25 = (struct sockaddr_x25 *)msg->msg_name; size_t copied; - int qbit, header_len = x25->neighbour->extended ? - X25_EXT_MIN_LEN : X25_STD_MIN_LEN; - + int qbit, header_len; struct sk_buff *skb; unsigned char *asmptr; int rc = -ENOTCONN; lock_sock(sk); + + if (x25->neighbour == NULL) + goto out; + + header_len = x25->neighbour->extended ? + X25_EXT_MIN_LEN : X25_STD_MIN_LEN; + /* * This works for seqpacket too. The receiver has ordered the queue for * us! We do one quick check first though -- 2.34.1