From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: 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. Co-developed-by: Qi Xi Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults") Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com Acked-by: Lorenzo Stoakes (ARM) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- tools/include/generated/asm-offsets.h | 0 tools/include/generated/asm/cpucap-defs.h | 0 tools/include/generated/asm/sysreg-defs.h | 0 3 files changed, 0 insertions(+), 0 deletions(-) create mode 100644 tools/include/generated/asm-offsets.h create mode 100644 tools/include/generated/asm/cpucap-defs.h create mode 100644 tools/include/generated/asm/sysreg-defs.h (limited to 'tools/include/generated') diff --git a/tools/include/generated/asm-offsets.h b/tools/include/generated/asm-offsets.h new file mode 100644 index 000000000..e69de29bb diff --git a/tools/include/generated/asm/cpucap-defs.h b/tools/include/generated/asm/cpucap-defs.h new file mode 100644 index 000000000..e69de29bb diff --git a/tools/include/generated/asm/sysreg-defs.h b/tools/include/generated/asm/sysreg-defs.h new file mode 100644 index 000000000..e69de29bb -- cgit v1.3.1