From: Eric Dumazet Date: Tue, 11 Oct 2022 21:27:29 +0000 (-0700) Subject: inet: ping: fix recent breakage X-Git-Tag: v6.1-rc5~182^2~12^2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=0d24148bd276ead5708ef56a4725580555bb48a3;p=platform%2Fkernel%2Flinux-starfive.git inet: ping: fix recent breakage Blamed commit broke the assumption used by ping sendmsg() that allocated skb would have MAX_HEADER bytes in skb->head. This patch changes the way ping works, by making sure the skb head contains space for the icmp header, and adjusting ping_getfrag() which was desperate about going past the icmp header :/ This is adopting what UDP does, mostly. syzbot is able to crash a host using both kfence and following repro in a loop. fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_ICMPV6) connect(fd, {sa_family=AF_INET6, sin6_port=htons(0), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::1", &sin6_addr), sin6_scope_id=0}, 28 sendmsg(fd, {msg_name=NULL, msg_namelen=0, msg_iov=[ {iov_base="\200\0\0\0\23\0\0\0\0\0\0\0\0\0"..., iov_len=65496}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0 When kfence triggers, skb->head only has 64 bytes, immediately followed by struct skb_shared_info (no extra headroom based on ksize(ptr)) Then icmpv6_push_pending_frames() is overwriting first bytes of skb_shinfo(skb), making nr_frags bigger than MAX_SKB_FRAGS, and/or setting shinfo->gso_size to a non zero value. If nr_frags is mangled, a crash happens in skb_release_data() If gso_size is mangled, we have the following report: lo: caps=(0x00000516401d7c69, 0x00000516401d7c69) WARNING: CPU: 0 PID: 7548 at net/core/dev.c:3239 skb_warn_bad_offload+0x119/0x230 net/core/dev.c:3239 Modules linked in: CPU: 0 PID: 7548 Comm: syz-executor268 Not tainted 6.0.0-syzkaller-02754-g557f050166e5 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022 RIP: 0010:skb_warn_bad_offload+0x119/0x230 net/core/dev.c:3239 Code: 70 03 00 00 e8 58 c3 24 fa 4c 8d a5 e8 00 00 00 e8 4c c3 24 fa 4c 89 e9 4c 89 e2 4c 89 f6 48 c7 c7 00 53 f5 8a e8 13 ac e7 01 <0f> 0b 5b 5d 41 5c 41 5d 41 5e e9 28 c3 24 fa e8 23 c3 24 fa 48 89 RSP: 0018:ffffc9000366f3e8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffff88807a9d9d00 RCX: 0000000000000000 RDX: ffff8880780c0000 RSI: ffffffff8160f6f8 RDI: fffff520006cde6f RBP: ffff888079952000 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000400 R11: 0000000000000000 R12: ffff8880799520e8 R13: ffff88807a9da070 R14: ffff888079952000 R15: 0000000000000000 FS: 0000555556be6300(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020010000 CR3: 000000006eb7b000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: gso_features_check net/core/dev.c:3521 [inline] netif_skb_features+0x83e/0xb90 net/core/dev.c:3554 validate_xmit_skb+0x2b/0xf10 net/core/dev.c:3659 __dev_queue_xmit+0x998/0x3ad0 net/core/dev.c:4248 dev_queue_xmit include/linux/netdevice.h:3008 [inline] neigh_hh_output include/net/neighbour.h:530 [inline] neigh_output include/net/neighbour.h:544 [inline] ip6_finish_output2+0xf97/0x1520 net/ipv6/ip6_output.c:134 __ip6_finish_output net/ipv6/ip6_output.c:195 [inline] ip6_finish_output+0x690/0x1160 net/ipv6/ip6_output.c:206 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip6_output+0x1ed/0x540 net/ipv6/ip6_output.c:227 dst_output include/net/dst.h:445 [inline] ip6_local_out+0xaf/0x1a0 net/ipv6/output_core.c:161 ip6_send_skb+0xb7/0x340 net/ipv6/ip6_output.c:1966 ip6_push_pending_frames+0xdd/0x100 net/ipv6/ip6_output.c:1986 icmpv6_push_pending_frames+0x2af/0x490 net/ipv6/icmp.c:303 ping_v6_sendmsg+0xc44/0x1190 net/ipv6/ping.c:190 inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:819 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:734 ____sys_sendmsg+0x712/0x8c0 net/socket.c:2482 ___sys_sendmsg+0x110/0x1b0 net/socket.c:2536 __sys_sendmsg+0xf3/0x1c0 net/socket.c:2565 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f21aab42b89 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fff1729d038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f21aab42b89 RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000003 RBP: 0000000000000000 R08: 000000000000000d R09: 000000000000000d R10: 000000000000000d R11: 0000000000000246 R12: 00007fff1729d050 R13: 00000000000f4240 R14: 0000000000021dd1 R15: 00007fff1729d044 Fixes: 47cf88993c91 ("net: unify alloclen calculation for paged requests") Reported-by: syzbot Signed-off-by: Eric Dumazet Cc: Pavel Begunkov Cc: Lorenzo Colitti Cc: Willem de Bruijn Cc: Maciej Żenczykowski Signed-off-by: David S. Miller --- diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c index 705672f..bde333b 100644 --- a/net/ipv4/ping.c +++ b/net/ipv4/ping.c @@ -617,21 +617,9 @@ int ping_getfrag(void *from, char *to, { struct pingfakehdr *pfh = from; - if (offset == 0) { - fraglen -= sizeof(struct icmphdr); - if (fraglen < 0) - BUG(); - if (!csum_and_copy_from_iter_full(to + sizeof(struct icmphdr), - fraglen, &pfh->wcheck, - &pfh->msg->msg_iter)) - return -EFAULT; - } else if (offset < sizeof(struct icmphdr)) { - BUG(); - } else { - if (!csum_and_copy_from_iter_full(to, fraglen, &pfh->wcheck, - &pfh->msg->msg_iter)) - return -EFAULT; - } + if (!csum_and_copy_from_iter_full(to, fraglen, &pfh->wcheck, + &pfh->msg->msg_iter)) + return -EFAULT; #if IS_ENABLED(CONFIG_IPV6) /* For IPv6, checksum each skb as we go along, as expected by @@ -842,7 +830,8 @@ back_from_confirm: pfh.family = AF_INET; err = ip_append_data(sk, &fl4, ping_getfrag, &pfh, len, - 0, &ipc, &rt, msg->msg_flags); + sizeof(struct icmphdr), &ipc, &rt, + msg->msg_flags); if (err) ip_flush_pending_frames(sk); else diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c index 5f2ef84..86c26e4 100644 --- a/net/ipv6/ping.c +++ b/net/ipv6/ping.c @@ -179,7 +179,7 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) lock_sock(sk); err = ip6_append_data(sk, ping_getfrag, &pfh, len, - 0, &ipc6, &fl6, rt, + sizeof(struct icmp6hdr), &ipc6, &fl6, rt, MSG_DONTWAIT); if (err) {