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

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 <xiqi2@huawei.com>

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) <ljs@kernel.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 32 insertions, 0 deletions

diff --git a/tools/perf/bench/Build b/tools/perf/bench/Build
new file mode 100644
index 000000000..67b76fe20
--- /dev/null
+++ b/tools/perf/bench/Build
@@ -0,0 +1,32 @@
+perf-bench-y += sched-messaging.o
+perf-bench-y += sched-pipe.o
+perf-bench-y += sched-seccomp-notify.o
+perf-bench-y += syscall.o
+perf-bench-y += mem-functions.o
+perf-bench-y += futex.o
+perf-bench-y += futex-hash.o
+perf-bench-y += futex-wake.o
+perf-bench-y += futex-wake-parallel.o
+perf-bench-y += futex-requeue.o
+perf-bench-y += futex-lock-pi.o
+perf-bench-y += epoll-wait.o
+perf-bench-y += epoll-ctl.o
+perf-bench-y += synthesize.o
+perf-bench-y += kallsyms-parse.o
+perf-bench-y += find-bit-bench.o
+perf-bench-y += inject-buildid.o
+perf-bench-y += evlist-open-close.o
+perf-bench-y += breakpoint.o
+perf-bench-y += pmu-scan.o
+perf-bench-y += uprobe.o
+
+perf-bench-$(CONFIG_X86_64) += mem-memcpy-x86-64-asm.o
+perf-bench-$(CONFIG_X86_64) += mem-memset-x86-64-asm.o
+
+perf-bench-$(CONFIG_NUMA) += numa.o
+
+ifeq ($(CONFIG_PERF_BPF_SKEL),y)
+include $(srctree)/tools/perf/bpf_skel.mak
+
+$(OUTPUT)bench/uprobe.o: $(SKEL_OUT)/bench_uprobe.skel.h
+endif