Bug 2535122 (CVE-2026-89905) - CVE-2026-89905 kernel: LoongArch: BPF: Move arena register slot below TCC context
Summary: CVE-2026-89905 kernel: LoongArch: BPF: Move arena register slot below TCC con...
Keywords:
Status: NEW
Alias: CVE-2026-89905
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-16 10:52 UTC by OSIDB Bzimport
Modified: 2026-11-04 18:56 UTC (History)
17 users (show)

Fixed In Version:
Clone Of:
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Description OSIDB Bzimport 2026-09-16 10:52:33 UTC
In the Linux kernel, the following vulnerability has been resolved:

LoongArch: BPF: Move arena register slot below TCC context

Currently, the stack layout places the optional arena register slot
above the tail call counter context. When arena_vm_start is dynamically
enabled, it shifts the relative offset of the tcc_ptr slot within the
stack frame, causing hardcoded tracking macros to mismatch and leading
to memory misalignment or corruption potentially.

To fix this, move the arena register save and restore sequences below
the tail call counter context slots in both build_prologue() and the
epilogue.

Update __build_epilogue() to insert a proper offset decrement to safely
skip the unneeded tcc_ptr reading block while accurately aligning with
the relocated arena slot at the very bottom.

With this patch, the tcc_ptr slot is always positioned at a fixed
distance directly underneath the base callee-saved registers that is
independent of whether the arena features are on.


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