CVE-2026-90303

Summary

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

ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults

When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set, a user fault may trigger show_pte() without any lock. If another thread in the same process concurrently calls munmap(), the page table pages may be freed while show_pte() is still traversing them, causing a use-after-free in show_pte().

If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table of PMD are freed when show_pte() is running.

Acquire mmap_write_lock() around show_pte() for user faults to fix the contention.

For user faults, additionally restrict that show_pte() is called only when the addr is a user-space address (addr < TASK_SIZE). This is because the lock of tsk->mm only protects the virtual memory of user address space, furthermore, dumping the page tables of a kernel-space address for user faults is unnecessary and may have security implications.

Keep everything unchanged for kernel faults, because the kernel is already in the "oops" state, acquiring a lock may risk a deadlock.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/ab14f07952adfe735d86a53518f8cd576dfd5892
• https://git.kernel.org/stable/c/07e4d5380f2a844ab7a1b440dde350caf561cbb0
• https://git.kernel.org/stable/c/2a14d7797a49a47bccd1a9327fd69da838dcb0dd
• https://git.kernel.org/stable/c/63e3c958a602d0896a101a897c2361878c266ca7
• https://git.kernel.org/stable/c/59bbf86d0ff9373bfa033ca123c1e924f09f1eba
• https://git.kernel.org/stable/c/c71f9a56520b419e55d173052629f2324deb5549
• https://git.kernel.org/stable/c/720408d98d9fb3c91a12090436734c8c61f04545
• https://git.kernel.org/stable/c/1039bffd6ae9c75b42b7d148d6c1106134107b66

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