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>

3 files changed, 47 insertions, 0 deletions

diff --git a/tools/include/uapi/asm/bitsperlong.h b/tools/include/uapi/asm/bitsperlong.h
new file mode 100644
index 000000000..c65267afc
--- /dev/null
+++ b/tools/include/uapi/asm/bitsperlong.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#if defined(__i386__) || defined(__x86_64__)
+#include "../../../arch/x86/include/uapi/asm/bitsperlong.h"
+#elif defined(__powerpc__)
+#include "../../../arch/powerpc/include/uapi/asm/bitsperlong.h"
+#elif defined(__s390__)
+#include "../../../arch/s390/include/uapi/asm/bitsperlong.h"
+#elif defined(__sparc__)
+#include "../../../arch/sparc/include/uapi/asm/bitsperlong.h"
+#elif defined(__mips__)
+#include "../../../arch/mips/include/uapi/asm/bitsperlong.h"
+#elif defined(__ia64__)
+#include "../../../arch/ia64/include/uapi/asm/bitsperlong.h"
+#elif defined(__alpha__)
+#include "../../../arch/alpha/include/uapi/asm/bitsperlong.h"
+#else
+#include <asm-generic/bitsperlong.h>
+#endif
diff --git a/tools/include/uapi/asm/bpf_perf_event.h b/tools/include/uapi/asm/bpf_perf_event.h
new file mode 100644
index 000000000..ff52668ab
--- /dev/null
+++ b/tools/include/uapi/asm/bpf_perf_event.h
@@ -0,0 +1,13 @@
+#if defined(__aarch64__)
+#include "../../arch/arm64/include/uapi/asm/bpf_perf_event.h"
+#elif defined(__arc__)
+#include "../../arch/arc/include/uapi/asm/bpf_perf_event.h"
+#elif defined(__s390__)
+#include "../../arch/s390/include/uapi/asm/bpf_perf_event.h"
+#elif defined(__riscv)
+#include "../../arch/riscv/include/uapi/asm/bpf_perf_event.h"
+#elif defined(__loongarch__)
+#include "../../arch/loongarch/include/uapi/asm/bpf_perf_event.h"
+#else
+#include <uapi/asm-generic/bpf_perf_event.h>
+#endif
diff --git a/tools/include/uapi/asm/errno.h b/tools/include/uapi/asm/errno.h
new file mode 100644
index 000000000..869379f91
--- /dev/null
+++ b/tools/include/uapi/asm/errno.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#if defined(__i386__) || defined(__x86_64__)
+#include "../../../arch/x86/include/uapi/asm/errno.h"
+#elif defined(__powerpc__)
+#include "../../../arch/powerpc/include/uapi/asm/errno.h"
+#elif defined(__sparc__)
+#include "../../../arch/sparc/include/uapi/asm/errno.h"
+#elif defined(__alpha__)
+#include "../../../arch/alpha/include/uapi/asm/errno.h"
+#elif defined(__mips__)
+#include "../../../arch/mips/include/uapi/asm/errno.h"
+#elif defined(__hppa__)
+#include "../../../arch/parisc/include/uapi/asm/errno.h"
+#else
+#include <asm-generic/errno.h>
+#endif