From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-46250: MIPS: Work around LLVM bug when gp is used as global register variable
Date: Wed, 3 Jun 2026 17:49:39 +0200 [thread overview]
Message-ID: <2026060334-CVE-2026-46250-736e@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
MIPS: Work around LLVM bug when gp is used as global register variable
On MIPS, __current_thread_info is defined as global register variable
locating in $gp, and is simply assigned with new address during kernel
relocation.
This however is broken with LLVM, which always restores $gp if it finds
$gp is clobbered in any form, including when intentionally through a
global register variable. This is against GCC's documentation[1], which
requires a callee-saved register used as global register variable not to
be restored if it's clobbered.
As a result, $gp will continue to point to the unrelocated kernel after
the epilog of relocate_kernel(), leading to an early crash in init_idle,
[ 0.000000] CPU 0 Unable to handle kernel paging request at virtual address 0000000000000000, epc == ffffffff81afada8, ra == ffffffff81afad90
[ 0.000000] Oops[#1]:
[ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Tainted: G W 6.19.0-rc5-00262-gd3eeb99bbc99-dirty #188 VOLUNTARY
[ 0.000000] Tainted: [W]=WARN
[ 0.000000] Hardware name: loongson,loongson64v-4core-virtio
[ 0.000000] $ 0 : 0000000000000000 0000000000000000 0000000000000001 0000000000000000
[ 0.000000] $ 4 : ffffffff80b80ec0 ffffffff80b53d48 0000000000000000 00000000000f4240
[ 0.000000] $ 8 : 0000000000000100 ffffffff81d82f80 ffffffff81d82f80 0000000000000001
[ 0.000000] $12 : 0000000000000000 ffffffff81776f58 00000000000005da 0000000000000002
[ 0.000000] $16 : ffffffff80b80e40 0000000000000000 ffffffff80b81614 9800000005dfbe80
[ 0.000000] $20 : 00000000540000e0 ffffffff81980000 0000000000000000 ffffffff80f81c80
[ 0.000000] $24 : 0000000000000a26 ffffffff8114fb90
[ 0.000000] $28 : ffffffff80b50000 ffffffff80b53d40 0000000000000000 ffffffff81afad90
[ 0.000000] Hi : 0000000000000000
[ 0.000000] Lo : 0000000000000000
[ 0.000000] epc : ffffffff81afada8 init_idle+0x130/0x270
[ 0.000000] ra : ffffffff81afad90 init_idle+0x118/0x270
[ 0.000000] Status: 540000e2 KX SX UX KERNEL EXL
[ 0.000000] Cause : 00000008 (ExcCode 02)
[ 0.000000] BadVA : 0000000000000000
[ 0.000000] PrId : 00006305 (ICT Loongson-3)
[ 0.000000] Process swapper (pid: 0, threadinfo=(____ptrval____), task=(____ptrval____), tls=0000000000000000)
[ 0.000000] Stack : 9800000005dfbf00 ffffffff8178e950 0000000000000000 0000000000000000
[ 0.000000] 0000000000000000 ffffffff81970000 000000000000003f ffffffff810a6528
[ 0.000000] 0000000000000001 9800000005dfbe80 9800000005dfbf00 ffffffff81980000
[ 0.000000] ffffffff810a6450 ffffffff81afb6c0 0000000000000000 ffffffff810a2258
[ 0.000000] ffffffff81d82ec8 ffffffff8198d010 ffffffff81b67e80 ffffffff8197dd98
[ 0.000000] ffffffff81d81c80 ffffffff81930000 0000000000000040 0000000000000000
[ 0.000000] 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 0.000000] 0000000000000000 000000000000009e ffffffff9fc01000 0000000000000000
[ 0.000000] 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 0.000000] 0000000000000000 ffffffff81ae86dc ffffffff81b3c741 0000000000000002
[ 0.000000] ...
[ 0.000000] Call Trace:
[ 0.000000] [<ffffffff81afada8>] init_idle+0x130/0x270
[ 0.000000] [<ffffffff81afb6c0>] sched_init+0x5c8/0x6c0
[ 0.000000] [<ffffffff81ae86dc>] start_kernel+0x27c/0x7a8
This bug has been reported to LLVM[2] and affects version from (at
least) 18 to 21. Let's work around this by using inline assembly to
assign $gp before a fix is widely available.
The Linux kernel CVE team has assigned CVE-2026-46250 to this issue.
Affected and fixed versions
===========================
Fixed in 5.10.252 with commit 05bff9b0ae095b2420cfebb4a96759a09334bec6
Fixed in 5.15.202 with commit 1fe3b402b1e97a1718df3be0a1d3eee20133e735
Fixed in 6.1.165 with commit 4dc65b40fb80c2020efbf139b9a38d30f9a37b92
Fixed in 6.6.128 with commit c0155dee51b9f5f48aaf5c71cae005eb0e36521f
Fixed in 6.12.75 with commit e3a6498a63394218561065a9a7a597a204f52f6a
Fixed in 6.18.14 with commit 561834f6d6f52b8a1791331e94b2aac753491d2a
Fixed in 6.19.4 with commit 9bc3b0ae5203aba650297fdf3e1e774125e423f2
Fixed in 7.0 with commit 30bfc2d6a1132a89a5f1c3b96c59cf3e4d076ea3
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-2026-46250
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:
arch/mips/kernel/relocate.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/05bff9b0ae095b2420cfebb4a96759a09334bec6
https://git.kernel.org/stable/c/1fe3b402b1e97a1718df3be0a1d3eee20133e735
https://git.kernel.org/stable/c/4dc65b40fb80c2020efbf139b9a38d30f9a37b92
https://git.kernel.org/stable/c/c0155dee51b9f5f48aaf5c71cae005eb0e36521f
https://git.kernel.org/stable/c/e3a6498a63394218561065a9a7a597a204f52f6a
https://git.kernel.org/stable/c/561834f6d6f52b8a1791331e94b2aac753491d2a
https://git.kernel.org/stable/c/9bc3b0ae5203aba650297fdf3e1e774125e423f2
https://git.kernel.org/stable/c/30bfc2d6a1132a89a5f1c3b96c59cf3e4d076ea3
reply other threads:[~2026-06-03 16:04 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2026060334-CVE-2026-46250-736e@gregkh \
--to=gregkh@linuxfoundation.org \
--cc=cve@kernel.org \
--cc=gregkh@kernel.org \
--cc=linux-cve-announce@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox