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authorEric Dumazet <edumazet@google.com>2023-03-30 20:45:02 +0300
committerJakub Kicinski <kuba@kernel.org>2023-04-01 07:37:06 +0300
commit7d63b67125382ff0ffdfca434acbc94a38bd092b (patch)
tree787ad5a24db6feb016b4baca844d4d0d3cdb7458 /net/ipv4
parentadef41b03b35839e5677aace628d02597f04a616 (diff)
downloadlinux-7d63b67125382ff0ffdfca434acbc94a38bd092b.tar.xz
icmp: guard against too small mtu
syzbot was able to trigger a panic [1] in icmp_glue_bits(), or more exactly in skb_copy_and_csum_bits() There is no repro yet, but I think the issue is that syzbot manages to lower device mtu to a small value, fooling __icmp_send() __icmp_send() must make sure there is enough room for the packet to include at least the headers. We might in the future refactor skb_copy_and_csum_bits() and its callers to no longer crash when something bad happens. [1] kernel BUG at net/core/skbuff.c:3343 ! invalid opcode: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 15766 Comm: syz-executor.0 Not tainted 6.3.0-rc4-syzkaller-00039-gffe78bbd5121 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 RIP: 0010:skb_copy_and_csum_bits+0x798/0x860 net/core/skbuff.c:3343 Code: f0 c1 c8 08 41 89 c6 e9 73 ff ff ff e8 61 48 d4 f9 e9 41 fd ff ff 48 8b 7c 24 48 e8 52 48 d4 f9 e9 c3 fc ff ff e8 c8 27 84 f9 <0f> 0b 48 89 44 24 28 e8 3c 48 d4 f9 48 8b 44 24 28 e9 9d fb ff ff RSP: 0018:ffffc90000007620 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 00000000000001e8 RCX: 0000000000000100 RDX: ffff8880276f6280 RSI: ffffffff87fdd138 RDI: 0000000000000005 RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000 R10: 00000000000001e8 R11: 0000000000000001 R12: 000000000000003c R13: 0000000000000000 R14: ffff888028244868 R15: 0000000000000b0e FS: 00007fbc81f1c700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2df43000 CR3: 00000000744db000 CR4: 0000000000150ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> icmp_glue_bits+0x7b/0x210 net/ipv4/icmp.c:353 __ip_append_data+0x1d1b/0x39f0 net/ipv4/ip_output.c:1161 ip_append_data net/ipv4/ip_output.c:1343 [inline] ip_append_data+0x115/0x1a0 net/ipv4/ip_output.c:1322 icmp_push_reply+0xa8/0x440 net/ipv4/icmp.c:370 __icmp_send+0xb80/0x1430 net/ipv4/icmp.c:765 ipv4_send_dest_unreach net/ipv4/route.c:1239 [inline] ipv4_link_failure+0x5a9/0x9e0 net/ipv4/route.c:1246 dst_link_failure include/net/dst.h:423 [inline] arp_error_report+0xcb/0x1c0 net/ipv4/arp.c:296 neigh_invalidate+0x20d/0x560 net/core/neighbour.c:1079 neigh_timer_handler+0xc77/0xff0 net/core/neighbour.c:1166 call_timer_fn+0x1a0/0x580 kernel/time/timer.c:1700 expire_timers+0x29b/0x4b0 kernel/time/timer.c:1751 __run_timers kernel/time/timer.c:2022 [inline] Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+d373d60fddbdc915e666@syzkaller.appspotmail.com Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20230330174502.1915328-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/icmp.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 8cebb476b3ab..b8607763d113 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -749,6 +749,11 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
room = 576;
room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
room -= sizeof(struct icmphdr);
+ /* Guard against tiny mtu. We need to include at least one
+ * IP network header for this message to make any sense.
+ */
+ if (room <= (int)sizeof(struct iphdr))
+ goto ende;
icmp_param.data_len = skb_in->len - icmp_param.offset;
if (icmp_param.data_len > room)