On Wed, Nov 1, 2023 at 1:02 AM Dmitry Safonov [off-list ref] wrote:

Hi Eric,

On 10/30/23 17:47, Dmitry Safonov wrote:

quoted

On 10/30/23 08:45, Eric Dumazet wrote:

quoted

syzbot managed to trigger a fault by sending TCP packets
with all flags being set.

BUG: KASAN: stack-out-of-bounds in string_nocheck lib/vsprintf.c:645 [inline]
BUG: KASAN: stack-out-of-bounds in string+0x394/0x3d0 lib/vsprintf.c:727
Read of size 1 at addr ffffc9000397f3f5 by task syz-executor299/5039

CPU: 1 PID: 5039 Comm: syz-executor299 Not tainted 6.6.0-rc7-syzkaller-02075-g55c900477f5b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xc4/0x620 mm/kasan/report.c:475
kasan_report+0xda/0x110 mm/kasan/report.c:588
string_nocheck lib/vsprintf.c:645 [inline]
string+0x394/0x3d0 lib/vsprintf.c:727
vsnprintf+0xc5f/0x1870 lib/vsprintf.c:2818
vprintk_store+0x3a0/0xb80 kernel/printk/printk.c:2191
vprintk_emit+0x14c/0x5f0 kernel/printk/printk.c:2288
vprintk+0x7b/0x90 kernel/printk/printk_safe.c:45
_printk+0xc8/0x100 kernel/printk/printk.c:2332
tcp_inbound_hash.constprop.0+0xdb2/0x10d0 include/net/tcp.h:2760
tcp_v6_rcv+0x2b31/0x34d0 net/ipv6/tcp_ipv6.c:1882
ip6_protocol_deliver_rcu+0x33b/0x13d0 net/ipv6/ip6_input.c:438
ip6_input_finish+0x14f/0x2f0 net/ipv6/ip6_input.c:483
NF_HOOK include/linux/netfilter.h:314 [inline]
NF_HOOK include/linux/netfilter.h:308 [inline]
ip6_input+0xce/0x440 net/ipv6/ip6_input.c:492
dst_input include/net/dst.h:461 [inline]
ip6_rcv_finish net/ipv6/ip6_input.c:79 [inline]
NF_HOOK include/linux/netfilter.h:314 [inline]
NF_HOOK include/linux/netfilter.h:308 [inline]
ipv6_rcv+0x563/0x720 net/ipv6/ip6_input.c:310
__netif_receive_skb_one_core+0x115/0x180 net/core/dev.c:5527
__netif_receive_skb+0x1f/0x1b0 net/core/dev.c:5641
netif_receive_skb_internal net/core/dev.c:5727 [inline]
netif_receive_skb+0x133/0x700 net/core/dev.c:5786
tun_rx_batched+0x429/0x780 drivers/net/tun.c:1579
tun_get_user+0x29e7/0x3bc0 drivers/net/tun.c:2002
tun_chr_write_iter+0xe8/0x210 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:1956 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x650/0xe40 fs/read_write.c:584
ksys_write+0x12f/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 2717b5adea9e ("net/tcp: Add tcp_hash_fail() ratelimited logs")
Reported-by: syzbot <redacted>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Dmitry Safonov <redacted>
Cc: Francesco Ruggeri <redacted>
Cc: David Ahern <dsahern@kernel.org>

Thanks for fixing this,
Reviewed-by: Dmitry Safonov <redacted>

quoted

---
 include/net/tcp_ao.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index a375a171ef3cb37ab1d8246c72c6a3e83f5c9184..5daf96a3dbee14bd3786e19ea4972e351058e6e7 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h

@@ -124,7 +124,7 @@ struct tcp_ao_info {
 #define tcp_hash_fail(msg, family, skb, fmt, ...)                   \
 do {                                                                        \
     const struct tcphdr *th = tcp_hdr(skb);                         \
-    char hdr_flags[5] = {};                                         \
+    char hdr_flags[5];                                              \
     char *f = hdr_flags;                                            \
                                                                     \
     if (th->fin)                                                    \

@@ -135,8 +135,7 @@ do {                                                                     \
             *f++ = 'R';                                             \
     if (th->ack)                                                    \
             *f++ = 'A';                                             \
-    if (f != hdr_flags)                                             \
-            *f = ' ';                                               \

Ah, that was clearly typo: I meant "*f = 0;"

Actually, after testing, I can see that the space was intended as well,
otherwise it "sticks" to L3index:
[  130.965652] TCP: AO key not found for (10.0.1.1, 56920)->(10.0.254.1,
7010) Skeyid: 100 L3index: 0
[  131.975116] TCP: AO hash is required, but not found for (10.0.1.1,
52686)->(10.0.254.1, 7011) SL3 index 0
[  132.984024] TCP: AO hash mismatch for (10.0.1.1, 51382)->(10.0.254.1,
7012) SL3index: 0
[  133.992221] TCP: Requested by the peer AO key id not found for
(10.0.1.1, 36548)->(10.0.254.1, 7013) SL3index: 0


If you don't mind, I'll send an updated version of your patch together
with some other small post-merge fixes this week.

I will send a v2, adding the space in the format like this :

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index 5daf96a3dbee14bd3786e19ea4972e351058e6e7..b90b4f8fb10fcbb31ddf65b825c098b215a91e67

100644

--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h

@@ -137,7 +137,7 @@ do {
                         \
                *f++ = 'A';                                             \
        *f = 0;                                                         \
        if ((family) == AF_INET) {                                      \
-               net_info_ratelimited("%s for (%pI4, %d)->(%pI4, %d)

%s" fmt "\n", \
+               net_info_ratelimited("%s for (%pI4, %d)->(%pI4, %d) %s
" fmt "\n", \
                                msg, &ip_hdr(skb)->saddr, ntohs(th->source), \
                                &ip_hdr(skb)->daddr, ntohs(th->dest),   \
                                hdr_flags, ##__VA_ARGS__);              \