CVE-2026-90303
UnknownSummary
In the Linux kernel on ARM, with CONFIG_DEBUG_USER=y and cmdline "user_debug=31", a user fault may trigger show_pte() without any lock. A concurrent munmap() in the same process can free page table pages while show_pte() traverses them, causing use-after-free, and with CONFIG_ARM_LPAE=y even a kernel panic. The fix acquires mmap_write_lock() around show_pte() for user faults and restricts it to user-space addresses (addr < TASK_SIZE).
Risk Assessment
This can lead to use-after-free or kernel panic, causing denial of service. It affects ARM systems with CONFIG_DEBUG_USER enabled and user_debug=31 set.
Recommendation
Update the Linux kernel to a version containing the ARM 9485/1 fix. Consider disabling CONFIG_DEBUG_USER or user_debug=31 if not required.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS