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Message-ID: <20241009091132.2136321-1-edumazet@google.com>
Date: Wed, 9 Oct 2024 09:11:32 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot+2ada1bc857496353be5a@...kaller.appspotmail.com
Subject: [PATCH net] slip: make slhc_remember() more robust against malicious packets
syzbot found that slhc_remember() was missing checks against
malicious packets [1].
slhc_remember() only checked the size of the packet was at least 20,
which is not good enough.
We need to make sure the packet includes the IPv4 and TCP header
that are supposed to be carried.
Add iph and th pointers to make the code more readable.
[1]
BUG: KMSAN: uninit-value in slhc_remember+0x2e8/0x7b0 drivers/net/slip/slhc.c:666
slhc_remember+0x2e8/0x7b0 drivers/net/slip/slhc.c:666
ppp_receive_nonmp_frame+0xe45/0x35e0 drivers/net/ppp/ppp_generic.c:2455
ppp_receive_frame drivers/net/ppp/ppp_generic.c:2372 [inline]
ppp_do_recv+0x65f/0x40d0 drivers/net/ppp/ppp_generic.c:2212
ppp_input+0x7dc/0xe60 drivers/net/ppp/ppp_generic.c:2327
pppoe_rcv_core+0x1d3/0x720 drivers/net/ppp/pppoe.c:379
sk_backlog_rcv+0x13b/0x420 include/net/sock.h:1113
__release_sock+0x1da/0x330 net/core/sock.c:3072
release_sock+0x6b/0x250 net/core/sock.c:3626
pppoe_sendmsg+0x2b8/0xb90 drivers/net/ppp/pppoe.c:903
sock_sendmsg_nosec net/socket.c:729 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:744
____sys_sendmsg+0x903/0xb60 net/socket.c:2602
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656
__sys_sendmmsg+0x3c1/0x960 net/socket.c:2742
__do_sys_sendmmsg net/socket.c:2771 [inline]
__se_sys_sendmmsg net/socket.c:2768 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768
x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Uninit was created at:
slab_post_alloc_hook mm/slub.c:4091 [inline]
slab_alloc_node mm/slub.c:4134 [inline]
kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4186
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587
__alloc_skb+0x363/0x7b0 net/core/skbuff.c:678
alloc_skb include/linux/skbuff.h:1322 [inline]
sock_wmalloc+0xfe/0x1a0 net/core/sock.c:2732
pppoe_sendmsg+0x3a7/0xb90 drivers/net/ppp/pppoe.c:867
sock_sendmsg_nosec net/socket.c:729 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:744
____sys_sendmsg+0x903/0xb60 net/socket.c:2602
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656
__sys_sendmmsg+0x3c1/0x960 net/socket.c:2742
__do_sys_sendmmsg net/socket.c:2771 [inline]
__se_sys_sendmmsg net/socket.c:2768 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768
x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
CPU: 0 UID: 0 PID: 5460 Comm: syz.2.33 Not tainted 6.12.0-rc2-syzkaller-00006-g87d6aab2389e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Fixes: b5451d783ade ("slip: Move the SLIP drivers")
Reported-by: syzbot+2ada1bc857496353be5a@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/670646db.050a0220.3f80e.0027.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
drivers/net/slip/slhc.c | 57 ++++++++++++++++++++++++-----------------
1 file changed, 34 insertions(+), 23 deletions(-)
diff --git a/drivers/net/slip/slhc.c b/drivers/net/slip/slhc.c
index 252cd757d3a2e5e1ed8c7dd059aa783ede48c953..ee9fd3a94b96fe11c02eb5da56deb876f6ac5a81 100644
--- a/drivers/net/slip/slhc.c
+++ b/drivers/net/slip/slhc.c
@@ -643,46 +643,57 @@ slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
int
slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
{
- struct cstate *cs;
- unsigned ihl;
-
+ const struct tcphdr *th;
unsigned char index;
+ struct iphdr *iph;
+ struct cstate *cs;
+ unsigned int ihl;
- if(isize < 20) {
- /* The packet is shorter than a legal IP header */
+ /* The packet is shorter than a legal IP header.
+ * Also make sure isize is positive.
+ */
+ if (isize < (int)sizeof(struct iphdr)) {
+runt:
comp->sls_i_runt++;
- return slhc_toss( comp );
+ return slhc_toss(comp);
}
+ iph = (struct iphdr *)icp;
/* Peek at the IP header's IHL field to find its length */
- ihl = icp[0] & 0xf;
- if(ihl < 20 / 4){
- /* The IP header length field is too small */
- comp->sls_i_runt++;
- return slhc_toss( comp );
- }
- index = icp[9];
- icp[9] = IPPROTO_TCP;
+ ihl = iph->ihl;
+ /* The IP header length field is too small,
+ * or packet is shorter than the IP header followed
+ * by minimal tcp header.
+ */
+ if (ihl < 5 || isize < ihl * 4 + sizeof(struct tcphdr))
+ goto runt;
+
+ index = iph->protocol;
+ iph->protocol = IPPROTO_TCP;
if (ip_fast_csum(icp, ihl)) {
/* Bad IP header checksum; discard */
comp->sls_i_badcheck++;
- return slhc_toss( comp );
+ return slhc_toss(comp);
}
- if(index > comp->rslot_limit) {
+ if (index > comp->rslot_limit) {
comp->sls_i_error++;
return slhc_toss(comp);
}
-
+ th = (struct tcphdr *)(icp + ihl * 4);
+ if (th->doff < sizeof(struct tcphdr) / 4)
+ goto runt;
+ if (isize < ihl * 4 + th->doff * 4)
+ goto runt;
/* Update local state */
cs = &comp->rstate[comp->recv_current = index];
comp->flags &=~ SLF_TOSS;
- memcpy(&cs->cs_ip,icp,20);
- memcpy(&cs->cs_tcp,icp + ihl*4,20);
+ memcpy(&cs->cs_ip, iph, sizeof(*iph));
+ memcpy(&cs->cs_tcp, th, sizeof(*th));
if (ihl > 5)
- memcpy(cs->cs_ipopt, icp + sizeof(struct iphdr), (ihl - 5) * 4);
- if (cs->cs_tcp.doff > 5)
- memcpy(cs->cs_tcpopt, icp + ihl*4 + sizeof(struct tcphdr), (cs->cs_tcp.doff - 5) * 4);
- cs->cs_hsize = ihl*2 + cs->cs_tcp.doff*2;
+ memcpy(cs->cs_ipopt, &iph[1], (ihl - 5) * 4);
+ if (th->doff > 5)
+ memcpy(cs->cs_tcpopt, &th[1], (th->doff - 5) * 4);
+ cs->cs_hsize = ihl*2 + th->doff*2;
cs->initialized = true;
/* Put headers back on packet
* Neither header checksum is recalculated
--
2.47.0.rc0.187.ge670bccf7e-goog
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