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/perf/util/pstack.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 tools/perf/util/pstack.c (limited to 'tools/perf/util/pstack.c') diff --git a/tools/perf/util/pstack.c b/tools/perf/util/pstack.c new file mode 100644 index 000000000..141ffa129 --- /dev/null +++ b/tools/perf/util/pstack.c @@ -0,0 +1,71 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Simple pointer stack + * + * (c) 2010 Arnaldo Carvalho de Melo + */ + +#include "pstack.h" +#include "debug.h" +#include +#include +#include +#include + +struct pstack { + unsigned short top; + unsigned short max_nr_entries; + void *entries[]; +}; + +struct pstack *pstack__new(unsigned short max_nr_entries) +{ + struct pstack *pstack = zalloc((sizeof(*pstack) + + max_nr_entries * sizeof(void *))); + if (pstack != NULL) + pstack->max_nr_entries = max_nr_entries; + return pstack; +} + +void pstack__delete(struct pstack *pstack) +{ + free(pstack); +} + +bool pstack__empty(const struct pstack *pstack) +{ + return pstack->top == 0; +} + +void pstack__remove(struct pstack *pstack, void *key) +{ + unsigned short i = pstack->top, last_index = pstack->top - 1; + + while (i-- != 0) { + if (pstack->entries[i] == key) { + if (i < last_index) + memmove(pstack->entries + i, + pstack->entries + i + 1, + (last_index - i) * sizeof(void *)); + --pstack->top; + return; + } + } + pr_err("%s: %p not on the pstack!\n", __func__, key); +} + +void pstack__push(struct pstack *pstack, void *key) +{ + if (pstack->top == pstack->max_nr_entries) { + pr_err("%s: top=%d, overflow!\n", __func__, pstack->top); + return; + } + pstack->entries[pstack->top++] = key; +} + +void *pstack__peek(struct pstack *pstack) +{ + if (pstack->top == 0) + return NULL; + return pstack->entries[pstack->top - 1]; +} -- cgit v1.3.1