MIPS: Work around LLVM bug when gp is used as global register variable

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Summary

CVECVE-2026-46250
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-03 18:16:25 UTC
Updated2026-06-03 18:16:25 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 05bff9b0ae095b2420cfebb4a96759a09334bec6 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 1fe3b402b1e97a1718df3be0a1d3eee20133e735 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 4dc65b40fb80c2020efbf139b9a38d30f9a37b92 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 c0155dee51b9f5f48aaf5c71cae005eb0e36521f git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 e3a6498a63394218561065a9a7a597a204f52f6a git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 561834f6d6f52b8a1791331e94b2aac753491d2a git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 9bc3b0ae5203aba650297fdf3e1e774125e423f2 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 30bfc2d6a1132a89a5f1c3b96c59cf3e4d076ea3 git Not specified
CNA Linux Linux affected 5.10.252 semver Not specified
CNA Linux Linux affected 5.15.202 semver Not specified
CNA Linux Linux affected 6.1.165 semver Not specified
CNA Linux Linux affected 6.6.128 semver Not specified
CNA Linux Linux affected 6.12.75 semver Not specified
CNA Linux Linux affected 6.18.14 semver Not specified
CNA Linux Linux affected 6.19.4 semver Not specified
CNA Linux Linux unaffected 5.10.252 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.202 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.165 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.128 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.75 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.14 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.4 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/c0155dee51b9f5f48aaf5c71cae005eb0e36521f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9bc3b0ae5203aba650297fdf3e1e774125e423f2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e3a6498a63394218561065a9a7a597a204f52f6a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/30bfc2d6a1132a89a5f1c3b96c59cf3e4d076ea3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4dc65b40fb80c2020efbf139b9a38d30f9a37b92 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1fe3b402b1e97a1718df3be0a1d3eee20133e735 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/561834f6d6f52b8a1791331e94b2aac753491d2a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/05bff9b0ae095b2420cfebb4a96759a09334bec6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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