linux-cve-announce - CVE-2022-49856: net: tun: call napi_schedule

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Message-ID: <2025050145-CVE-2022-49856-4dc0@gregkh>
Date: Thu,  1 May 2025 16:10:46 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-49856: net: tun: call napi_schedule_prep() to ensure we own a napi

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

net: tun: call napi_schedule_prep() to ensure we own a napi

A recent patch exposed another issue in napi_get_frags()
caught by syzbot [1]

Before feeding packets to GRO, and calling napi_complete()
we must first grab NAPI_STATE_SCHED.

[1]
WARNING: CPU: 0 PID: 3612 at net/core/dev.c:6076 napi_complete_done+0x45b/0x880 net/core/dev.c:6076
Modules linked in:
CPU: 0 PID: 3612 Comm: syz-executor408 Not tainted 6.1.0-rc3-syzkaller-00175-g1118b2049d77 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:napi_complete_done+0x45b/0x880 net/core/dev.c:6076
Code: c1 ea 03 0f b6 14 02 4c 89 f0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 24 04 00 00 41 89 5d 1c e9 73 fc ff ff e8 b5 53 22 fa <0f> 0b e9 82 fe ff ff e8 a9 53 22 fa 48 8b 5c 24 08 31 ff 48 89 de
RSP: 0018:ffffc90003c4f920 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000030 RCX: 0000000000000000
RDX: ffff8880251c0000 RSI: ffffffff875a58db RDI: 0000000000000007
RBP: 0000000000000001 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff888072d02628
R13: ffff888072d02618 R14: ffff888072d02634 R15: 0000000000000000
FS: 0000555555f13300(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055c44d3892b8 CR3: 00000000172d2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
napi_complete include/linux/netdevice.h:510 [inline]
tun_get_user+0x206d/0x3a60 drivers/net/tun.c:1980
tun_chr_write_iter+0xdb/0x200 drivers/net/tun.c:2027
call_write_iter include/linux/fs.h:2191 [inline]
do_iter_readv_writev+0x20b/0x3b0 fs/read_write.c:735
do_iter_write+0x182/0x700 fs/read_write.c:861
vfs_writev+0x1aa/0x630 fs/read_write.c:934
do_writev+0x133/0x2f0 fs/read_write.c:977
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+0x63/0xcd
RIP: 0033:0x7f37021a3c19

The Linux kernel CVE team has assigned CVE-2022-49856 to this issue.


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

	Issue fixed in mainline with commit 07d120a

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-2022-49856
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:
	drivers/net/tun.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/310f0855352ee4b2eb38855c99185c23e6e1496b
	https://git.kernel.org/stable/c/30b0263d0366ea63aa7cad0407dfd945cc348580
	https://git.kernel.org/stable/c/534762e261c84d43e5d56a780e40278b94c20540
	https://git.kernel.org/stable/c/9132fa043f96ac545254ab326db5c6fd47d54acb
	https://git.kernel.org/stable/c/999550c8cbb3fcb535f542d652fe1cb936839e5f
	https://git.kernel.org/stable/c/07d120aa33cc9d9115753d159f64d20c94458781