linux-cve-announce - CVE-2023-53186: skbuff: Fix a race between coalescing and releasing SKBs

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Message-ID: <2025091557-CVE-2023-53186-25a4@gregkh>
Date: Mon, 15 Sep 2025 16:02:40 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53186: skbuff: Fix a race between coalescing and releasing SKBs

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

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

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

skbuff: Fix a race between coalescing and releasing SKBs

Commit 1effe8ca4e34 ("skbuff: fix coalescing for page_pool fragment
recycling") allowed coalescing to proceed with non page pool page and page
pool page when @from is cloned, i.e.

to->pp_recycle    --> false
from->pp_recycle  --> true
skb_cloned(from)  --> true

However, it actually requires skb_cloned(@from) to hold true until
coalescing finishes in this situation. If the other cloned SKB is
released while the merging is in process, from_shinfo->nr_frags will be
set to 0 toward the end of the function, causing the increment of frag
page _refcount to be unexpectedly skipped resulting in inconsistent
reference counts. Later when SKB(@to) is released, it frees the page
directly even though the page pool page is still in use, leading to
use-after-free or double-free errors. So it should be prohibited.

The double-free error message below prompted us to investigate:
BUG: Bad page state in process swapper/1  pfn:0e0d1
page:00000000c6548b28 refcount:-1 mapcount:0 mapping:0000000000000000
index:0x2 pfn:0xe0d1
flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff)
raw: 000fffffc0000000 0000000000000000 ffffffff00000101 0000000000000000
raw: 0000000000000002 0000000000000000 ffffffffffffffff 0000000000000000
page dumped because: nonzero _refcount

CPU: 1 PID: 0 Comm: swapper/1 Tainted: G            E      6.2.0+
Call Trace:
 <IRQ>
dump_stack_lvl+0x32/0x50
bad_page+0x69/0xf0
free_pcp_prepare+0x260/0x2f0
free_unref_page+0x20/0x1c0
skb_release_data+0x10b/0x1a0
napi_consume_skb+0x56/0x150
net_rx_action+0xf0/0x350
? __napi_schedule+0x79/0x90
__do_softirq+0xc8/0x2b1
__irq_exit_rcu+0xb9/0xf0
common_interrupt+0x82/0xa0
</IRQ>
<TASK>
asm_common_interrupt+0x22/0x40
RIP: 0010:default_idle+0xb/0x20

The Linux kernel CVE team has assigned CVE-2023-53186 to this issue.

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

	Issue introduced in 5.15 with commit 53e0961da1c7bbdabd1abebb20de403ec237ec09 and fixed in 5.15.108 with commit 906a6689bb0191ad2a44131a3377006aa098af59
	Issue introduced in 5.15 with commit 53e0961da1c7bbdabd1abebb20de403ec237ec09 and fixed in 6.1.25 with commit 71850b5af92da21b4862a9bc55bda61091247d00
	Issue introduced in 5.15 with commit 53e0961da1c7bbdabd1abebb20de403ec237ec09 and fixed in 6.2.12 with commit 5f692c992a3bb9a8018e3488098b401a4229e7ec
	Issue introduced in 5.15 with commit 53e0961da1c7bbdabd1abebb20de403ec237ec09 and fixed in 6.3 with commit 0646dc31ca886693274df5749cd0c8c1eaaeb5ca

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-2023-53186
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:
	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/906a6689bb0191ad2a44131a3377006aa098af59
	https://git.kernel.org/stable/c/71850b5af92da21b4862a9bc55bda61091247d00
	https://git.kernel.org/stable/c/5f692c992a3bb9a8018e3488098b401a4229e7ec
	https://git.kernel.org/stable/c/0646dc31ca886693274df5749cd0c8c1eaaeb5ca