From a98f91758995cb59611e61318dddd8a6956b52c3 Mon Sep 17 00:00:00 2001 From: Dave Jones Date: Thu, 22 Dec 2016 11:16:22 -0500 Subject: [PATCH] ipv6: handle -EFAULT from skb_copy_bits By setting certain socket options on ipv6 raw sockets, we can confuse the length calculation in rawv6_push_pending_frames triggering a BUG_ON. RIP: 0010:[] [] rawv6_sendmsg+0xc30/0xc40 RSP: 0018:ffff881f6c4a7c18 EFLAGS: 00010282 RAX: 00000000fffffff2 RBX: ffff881f6c681680 RCX: 0000000000000002 RDX: ffff881f6c4a7cf8 RSI: 0000000000000030 RDI: ffff881fed0f6a00 RBP: ffff881f6c4a7da8 R08: 0000000000000000 R09: 0000000000000009 R10: ffff881fed0f6a00 R11: 0000000000000009 R12: 0000000000000030 R13: ffff881fed0f6a00 R14: ffff881fee39ba00 R15: ffff881fefa93a80 Call Trace: [] ? unmap_page_range+0x693/0x830 [] inet_sendmsg+0x67/0xa0 [] sock_sendmsg+0x38/0x50 [] SYSC_sendto+0xef/0x170 [] SyS_sendto+0xe/0x10 [] do_syscall_64+0x50/0xa0 [] entry_SYSCALL64_slow_path+0x25/0x25 Handle by jumping to the failure path if skb_copy_bits gets an EFAULT. Reproducer: #include #include #include #include #include #include #include #define LEN 504 int main(int argc, char* argv[]) { int fd; int zero = 0; char buf[LEN]; memset(buf, 0, LEN); fd = socket(AF_INET6, SOCK_RAW, 7); setsockopt(fd, SOL_IPV6, IPV6_CHECKSUM, &zero, 4); setsockopt(fd, SOL_IPV6, IPV6_DSTOPTS, &buf, LEN); sendto(fd, buf, 1, 0, (struct sockaddr *) buf, 110); } Signed-off-by: Dave Jones Signed-off-by: David S. Miller --- net/ipv6/raw.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c index 291ebc260e70..ea89073c8247 100644 --- a/net/ipv6/raw.c +++ b/net/ipv6/raw.c @@ -591,7 +591,11 @@ static int rawv6_push_pending_frames(struct sock *sk, struct flowi6 *fl6, } offset += skb_transport_offset(skb); - BUG_ON(skb_copy_bits(skb, offset, &csum, 2)); + err = skb_copy_bits(skb, offset, &csum, 2); + if (err < 0) { + ip6_flush_pending_frames(sk); + goto out; + } /* in case cksum was not initialized */ if (unlikely(csum)) -- 2.30.2