linux-cve-announce - CVE-2025-21855: ibmvnic: Don't reference skb after sending to VIOS

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Message-ID: <2025031214-CVE-2025-21855-2d67@gregkh>
Date: Wed, 12 Mar 2025 10:42:21 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21855: ibmvnic: Don't reference skb after sending to VIOS

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

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

ibmvnic: Don't reference skb after sending to VIOS

Previously, after successfully flushing the xmit buffer to VIOS,
the tx_bytes stat was incremented by the length of the skb.

It is invalid to access the skb memory after sending the buffer to
the VIOS because, at any point after sending, the VIOS can trigger
an interrupt to free this memory. A race between reading skb->len
and freeing the skb is possible (especially during LPM) and will
result in use-after-free:
 ==================================================================
 BUG: KASAN: slab-use-after-free in ibmvnic_xmit+0x75c/0x1808 [ibmvnic]
 Read of size 4 at addr c00000024eb48a70 by task hxecom/14495
 <...>
 Call Trace:
 [c000000118f66cf0] [c0000000018cba6c] dump_stack_lvl+0x84/0xe8 (unreliable)
 [c000000118f66d20] [c0000000006f0080] print_report+0x1a8/0x7f0
 [c000000118f66df0] [c0000000006f08f0] kasan_report+0x128/0x1f8
 [c000000118f66f00] [c0000000006f2868] __asan_load4+0xac/0xe0
 [c000000118f66f20] [c0080000046eac84] ibmvnic_xmit+0x75c/0x1808 [ibmvnic]
 [c000000118f67340] [c0000000014be168] dev_hard_start_xmit+0x150/0x358
 <...>
 Freed by task 0:
 kasan_save_stack+0x34/0x68
 kasan_save_track+0x2c/0x50
 kasan_save_free_info+0x64/0x108
 __kasan_mempool_poison_object+0x148/0x2d4
 napi_skb_cache_put+0x5c/0x194
 net_tx_action+0x154/0x5b8
 handle_softirqs+0x20c/0x60c
 do_softirq_own_stack+0x6c/0x88
 <...>
 The buggy address belongs to the object at c00000024eb48a00 which
  belongs to the cache skbuff_head_cache of size 224
==================================================================

The Linux kernel CVE team has assigned CVE-2025-21855 to this issue.

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

	Issue introduced in 4.5 with commit 032c5e82847a2214c3196a90f0aeba0ce252de58 and fixed in 6.1.130 with commit 501ac6a7e21b82e05207c6b4449812d82820f306
	Issue introduced in 4.5 with commit 032c5e82847a2214c3196a90f0aeba0ce252de58 and fixed in 6.6.80 with commit 093b0e5c90592773863f300b908b741622eef597
	Issue introduced in 4.5 with commit 032c5e82847a2214c3196a90f0aeba0ce252de58 and fixed in 6.12.17 with commit 25dddd01dcc8ef3acff964dbb32eeb0d89f098e9
	Issue introduced in 4.5 with commit 032c5e82847a2214c3196a90f0aeba0ce252de58 and fixed in 6.13.5 with commit abaff2717470e4b5b7c0c3a90e128b211a23da09
	Issue introduced in 4.5 with commit 032c5e82847a2214c3196a90f0aeba0ce252de58 and fixed in 6.14-rc4 with commit bdf5d13aa05ec314d4385b31ac974d6c7e0997c9

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-2025-21855
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/ethernet/ibm/ibmvnic.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/501ac6a7e21b82e05207c6b4449812d82820f306
	https://git.kernel.org/stable/c/093b0e5c90592773863f300b908b741622eef597
	https://git.kernel.org/stable/c/25dddd01dcc8ef3acff964dbb32eeb0d89f098e9
	https://git.kernel.org/stable/c/abaff2717470e4b5b7c0c3a90e128b211a23da09
	https://git.kernel.org/stable/c/bdf5d13aa05ec314d4385b31ac974d6c7e0997c9