This is a note to let you know that I've just added the patch titled
mptcp: fix TCP options overflow.
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mptcp-fix-tcp-options-overflow.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit dd019501221313c2d531443b7e10d6942ee49785
Author: Paolo Abeni <pabeni@xxxxxxxxxx>
Date: Sat Dec 21 09:51:46 2024 +0100
mptcp: fix TCP options overflow.
[ Upstream commit cbb26f7d8451fe56ccac802c6db48d16240feebd ]
Syzbot reported the following splat:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 1 UID: 0 PID: 5836 Comm: sshd Not tainted 6.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
RIP: 0010:_compound_head include/linux/page-flags.h:242 [inline]
RIP: 0010:put_page+0x23/0x260 include/linux/mm.h:1552
Code: 90 90 90 90 90 90 90 55 41 57 41 56 53 49 89 fe 48 bd 00 00 00 00 00 fc ff df e8 f8 5e 12 f8 49 8d 5e 08 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 08 48 89 df e8 8f c7 78 f8 48 8b 1b 48 89 de 48 83
RSP: 0000:ffffc90003916c90 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000008 RCX: ffff888030458000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffffffff898ca81d R09: 1ffff110054414ac
R10: dffffc0000000000 R11: ffffed10054414ad R12: 0000000000000007
R13: ffff88802a20a542 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f34f496e800(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9d6ec9ec28 CR3: 000000004d260000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
skb_page_unref include/linux/skbuff_ref.h:43 [inline]
__skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
skb_release_data+0x483/0x8a0 net/core/skbuff.c:1119
skb_release_all net/core/skbuff.c:1190 [inline]
__kfree_skb+0x55/0x70 net/core/skbuff.c:1204
tcp_clean_rtx_queue net/ipv4/tcp_input.c:3436 [inline]
tcp_ack+0x2442/0x6bc0 net/ipv4/tcp_input.c:4032
tcp_rcv_state_process+0x8eb/0x44e0 net/ipv4/tcp_input.c:6805
tcp_v4_do_rcv+0x77d/0xc70 net/ipv4/tcp_ipv4.c:1939
tcp_v4_rcv+0x2dc0/0x37f0 net/ipv4/tcp_ipv4.c:2351
ip_protocol_deliver_rcu+0x22e/0x440 net/ipv4/ip_input.c:205
ip_local_deliver_finish+0x341/0x5f0 net/ipv4/ip_input.c:233
NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
__netif_receive_skb_one_core net/core/dev.c:5672 [inline]
__netif_receive_skb+0x2bf/0x650 net/core/dev.c:5785
process_backlog+0x662/0x15b0 net/core/dev.c:6117
__napi_poll+0xcb/0x490 net/core/dev.c:6883
napi_poll net/core/dev.c:6952 [inline]
net_rx_action+0x89b/0x1240 net/core/dev.c:7074
handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:561
__do_softirq kernel/softirq.c:595 [inline]
invoke_softirq kernel/softirq.c:435 [inline]
__irq_exit_rcu+0xf7/0x220 kernel/softirq.c:662
irq_exit_rcu+0x9/0x30 kernel/softirq.c:678
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
sysvec_apic_timer_interrupt+0x57/0xc0 arch/x86/kernel/apic/apic.c:1049
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0033:0x7f34f4519ad5
Code: 85 d2 74 0d 0f 10 02 48 8d 54 24 20 0f 11 44 24 20 64 8b 04 25 18 00 00 00 85 c0 75 27 41 b8 08 00 00 00 b8 0f 01 00 00 0f 05 <48> 3d 00 f0 ff ff 76 75 48 8b 15 24 73 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffec5b32ce0 EFLAGS: 00000246
RAX: 0000000000000001 RBX: 00000000000668a0 RCX: 00007f34f4519ad5
RDX: 00007ffec5b32d00 RSI: 0000000000000004 RDI: 0000564f4bc6cae0
RBP: 0000564f4bc6b5a0 R08: 0000000000000008 R09: 0000000000000000
R10: 00007ffec5b32de8 R11: 0000000000000246 R12: 0000564f48ea8aa4
R13: 0000000000000001 R14: 0000564f48ea93e8 R15: 00007ffec5b32d68
</TASK>
Eric noted a probable shinfo->nr_frags corruption, which indeed
occurs.
The root cause is a buggy MPTCP option len computation in some
circumstances: the ADD_ADDR option should be mutually exclusive
with DSS since the blamed commit.
Still, mptcp_established_options_add_addr() tries to set the
relevant info in mptcp_out_options, if the remaining space is
large enough even when DSS is present.
Since the ADD_ADDR infos and the DSS share the same union
fields, adding first corrupts the latter. In the worst-case
scenario, such corruption increases the DSS binary layout,
exceeding the computed length and possibly overwriting the
skb shared info.
Address the issue by enforcing mutual exclusion in
mptcp_established_options_add_addr(), too.
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: syzbot+38a095a81f30d82884c1@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/538
Fixes: 1bff1e43a30e ("mptcp: optimize out option generation")
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://patch.msgid.link/025d9df8cde3c9a557befc47e9bc08fbbe3476e5.1734771049.git.pabeni@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 31bec175886c..bdabc5e889b7 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -662,8 +662,15 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
&echo, &drop_other_suboptions))
return false;
+ /*
+ * Later on, mptcp_write_options() will enforce mutually exclusion with
+ * DSS, bail out if such option is set and we can't drop it.
+ */
if (drop_other_suboptions)
remaining += opt_size;
+ else if (opts->suboptions & OPTION_MPTCP_DSS)
+ return false;
+
len = mptcp_add_addr_len(opts->addr.family, echo, !!opts->addr.port);
if (remaining < len)
return false;
