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 ...

Classification

CVE ID: CVE-2025-21855

Affected Products

Vendor: Linux, Linux

Product: Linux, Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.02% (probability of being exploited)

EPSS Percentile: 2.2% (scored less or equal to compared to others)

EPSS Date: 2025-04-10 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-21855
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

Timeline