linux-cve-announce - CVE-2022-49142: net: preserve skb_end_offset() in skb_unclone

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Message-ID: <2025022607-CVE-2022-49142-b3b9@gregkh>
Date: Wed, 26 Feb 2025 02:55:47 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49142: net: preserve skb_end_offset() in skb_unclone_keeptruesize()

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net: preserve skb_end_offset() in skb_unclone_keeptruesize()

syzbot found another way to trigger the infamous WARN_ON_ONCE(delta < len)
in skb_try_coalesce() [1]

I was able to root cause the issue to kfence.

When kfence is in action, the following assertion is no longer true:

int size = xxxx;
void *ptr1 = kmalloc(size, gfp);
void *ptr2 = kmalloc(size, gfp);

if (ptr1 && ptr2)
	ASSERT(ksize(ptr1) == ksize(ptr2));

We attempted to fix these issues in the blamed commits, but forgot
that TCP was possibly shifting data after skb_unclone_keeptruesize()
has been used, notably from tcp_retrans_try_collapse().

So we not only need to keep same skb->truesize value,
we also need to make sure TCP wont fill new tailroom
that pskb_expand_head() was able to get from a
addr = kmalloc(...) followed by ksize(addr)

Split skb_unclone_keeptruesize() into two parts:

1) Inline skb_unclone_keeptruesize() for the common case,
   when skb is not cloned.

2) Out of line __skb_unclone_keeptruesize() for the 'slow path'.

WARNING: CPU: 1 PID: 6490 at net/core/skbuff.c:5295 skb_try_coalesce+0x1235/0x1560 net/core/skbuff.c:5295
Modules linked in:
CPU: 1 PID: 6490 Comm: syz-executor161 Not tainted 5.17.0-rc4-syzkaller-00229-g4f12b742eb2b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:skb_try_coalesce+0x1235/0x1560 net/core/skbuff.c:5295
Code: bf 01 00 00 00 0f b7 c0 89 c6 89 44 24 20 e8 62 24 4e fa 8b 44 24 20 83 e8 01 0f 85 e5 f0 ff ff e9 87 f4 ff ff e8 cb 20 4e fa <0f> 0b e9 06 f9 ff ff e8 af b2 95 fa e9 69 f0 ff ff e8 95 b2 95 fa
RSP: 0018:ffffc900063af268 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 00000000ffffffd5 RCX: 0000000000000000
RDX: ffff88806fc05700 RSI: ffffffff872abd55 RDI: 0000000000000003
RBP: ffff88806e675500 R08: 00000000ffffffd5 R09: 0000000000000000
R10: ffffffff872ab659 R11: 0000000000000000 R12: ffff88806dd554e8
R13: ffff88806dd9bac0 R14: ffff88806dd9a2c0 R15: 0000000000000155
FS:  00007f18014f9700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020002000 CR3: 000000006be7a000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 tcp_try_coalesce net/ipv4/tcp_input.c:4651 [inline]
 tcp_try_coalesce+0x393/0x920 net/ipv4/tcp_input.c:4630
 tcp_queue_rcv+0x8a/0x6e0 net/ipv4/tcp_input.c:4914
 tcp_data_queue+0x11fd/0x4bb0 net/ipv4/tcp_input.c:5025
 tcp_rcv_established+0x81e/0x1ff0 net/ipv4/tcp_input.c:5947
 tcp_v4_do_rcv+0x65e/0x980 net/ipv4/tcp_ipv4.c:1719
 sk_backlog_rcv include/net/sock.h:1037 [inline]
 __release_sock+0x134/0x3b0 net/core/sock.c:2779
 release_sock+0x54/0x1b0 net/core/sock.c:3311
 sk_wait_data+0x177/0x450 net/core/sock.c:2821
 tcp_recvmsg_locked+0xe28/0x1fd0 net/ipv4/tcp.c:2457
 tcp_recvmsg+0x137/0x610 net/ipv4/tcp.c:2572
 inet_recvmsg+0x11b/0x5e0 net/ipv4/af_inet.c:850
 sock_recvmsg_nosec net/socket.c:948 [inline]
 sock_recvmsg net/socket.c:966 [inline]
 sock_recvmsg net/socket.c:962 [inline]
 ____sys_recvmsg+0x2c4/0x600 net/socket.c:2632
 ___sys_recvmsg+0x127/0x200 net/socket.c:2674
 __sys_recvmsg+0xe2/0x1a0 net/socket.c:2704
 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+0x44/0xae

The Linux kernel CVE team has assigned CVE-2022-49142 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.12 with commit 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 and fixed in 5.15.33 with commit 23629b673b780d967b88a850b1518cf0f0ffc6aa
	Issue introduced in 5.12 with commit 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 and fixed in 5.16.19 with commit a9a6d30264327d8ff7f23da33e7a77ffb793fa3f
	Issue introduced in 5.12 with commit 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 and fixed in 5.17.2 with commit a903e516f5df44b46d526b403d93e7be1a425538
	Issue introduced in 5.12 with commit 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 and fixed in 5.18 with commit 2b88cba55883eaafbc9b7cbff0b2c7cdba71ed01
	Issue introduced in 4.4.260 with commit 7118945cdf0d4b5a76eb4f5f330ac6f48d372025
	Issue introduced in 4.9.260 with commit ec697f7f3f6a89d4dd1af113587d0330b5a033e8
	Issue introduced in 4.14.224 with commit 7582edf28f5d1f0a4d2f7abdb7d9560d09fd41b5
	Issue introduced in 4.19.179 with commit 5d55a6a46a7f70bc1d270c50200edd3096cb380c
	Issue introduced in 5.4.103 with commit e6af7cb64b7b37b8a371acdbe33a636496ffb5a4
	Issue introduced in 5.10.21 with commit 97ff09a7ed484fef2b1bbc103857444b7332fca8
	Issue introduced in 5.11.4 with commit bf5a58d143d7899d2c89e585be6e98ec81fe9683

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-49142
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	include/linux/skbuff.h
	net/core/skbuff.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/23629b673b780d967b88a850b1518cf0f0ffc6aa
	https://git.kernel.org/stable/c/a9a6d30264327d8ff7f23da33e7a77ffb793fa3f
	https://git.kernel.org/stable/c/a903e516f5df44b46d526b403d93e7be1a425538
	https://git.kernel.org/stable/c/2b88cba55883eaafbc9b7cbff0b2c7cdba71ed01