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, 36 insertions, 0 deletions

diff --git a/tools/perf/MANIFEST b/tools/perf/MANIFEST
new file mode 100644
index 000000000..34af57b8e
--- /dev/null
+++ b/tools/perf/MANIFEST
@@ -0,0 +1,36 @@
+COPYING
+LICENSES/preferred/GPL-2.0
+arch/arm64/tools/gen-sysreg.awk
+arch/arm64/tools/syscall_64.tbl
+arch/arm64/tools/sysreg
+arch/*/include/uapi/asm/bpf_perf_event.h
+include/uapi/asm-generic/Kbuild
+tools/perf
+tools/arch
+tools/scripts
+tools/build
+tools/include
+tools/lib/api
+tools/lib/bpf
+tools/lib/subcmd
+tools/lib/perf
+tools/lib/argv_split.c
+tools/lib/ctype.c
+tools/lib/hweight.c
+tools/lib/rbtree.c
+tools/lib/string.c
+tools/lib/symbol
+tools/lib/find_bit.c
+tools/lib/bitmap.c
+tools/lib/list_sort.c
+tools/lib/str_error_r.c
+tools/lib/vsprintf.c
+tools/lib/zalloc.c
+scripts/bpf_doc.py
+scripts/Kbuild.include
+scripts/Makefile.asm-headers
+scripts/syscall.tbl
+scripts/syscallhdr.sh
+tools/bpf/bpftool
+kernel/bpf/disasm.c
+kernel/bpf/disasm.h