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>

6 files changed, 181 insertions, 0 deletions

diff --git a/Documentation/features/vm/ELF-ASLR/arch-support.txt b/Documentation/features/vm/ELF-ASLR/arch-support.txt
new file mode 100644
index 000000000..57406c0d5
--- /dev/null
+++ b/Documentation/features/vm/ELF-ASLR/arch-support.txt
@@ -0,0 +1,31 @@
+#
+# Feature name:          ELF-ASLR
+#         Kconfig:       ARCH_HAS_ELF_RANDOMIZE
+#         Kconfig:       ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
+#         description:   arch randomizes the stack, heap and binary images of ELF binaries
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: |  ok  |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/vm/THP/arch-support.txt b/Documentation/features/vm/THP/arch-support.txt
new file mode 100644
index 000000000..b4a5ce169
--- /dev/null
+++ b/Documentation/features/vm/THP/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          THP
+#         Kconfig:       HAVE_ARCH_TRANSPARENT_HUGEPAGE
+#         description:   arch supports transparent hugepages
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ..  |
+    |     hexagon: |  ..  |
+    |   loongarch: |  ok  |
+    |        m68k: |  ..  |
+    |  microblaze: |  ..  |
+    |        mips: |  ok  |
+    |       nios2: |  ..  |
+    |    openrisc: |  ..  |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ..  |
+    |       sparc: |  ok  |
+    |          um: |  ..  |
+    |         x86: |  ok  |
+    |      xtensa: |  ..  |
+    -----------------------
diff --git a/Documentation/features/vm/TLB/arch-support.txt b/Documentation/features/vm/TLB/arch-support.txt
new file mode 100644
index 000000000..d222bd3ee
--- /dev/null
+++ b/Documentation/features/vm/TLB/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          batch-unmap-tlb-flush
+#         Kconfig:       ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
+#         description:   arch supports deferral of TLB flush until multiple pages are unmapped
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: | TODO |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: | TODO |
+    |        m68k: |  ..  |
+    |  microblaze: |  ..  |
+    |        mips: | TODO |
+    |       nios2: |  ..  |
+    |    openrisc: |  ..  |
+    |      parisc: | TODO |
+    |     powerpc: | TODO |
+    |       riscv: |  ok  |
+    |        s390: | TODO |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: |  ..  |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/vm/huge-vmap/arch-support.txt b/Documentation/features/vm/huge-vmap/arch-support.txt
new file mode 100644
index 000000000..2d6de7b04
--- /dev/null
+++ b/Documentation/features/vm/huge-vmap/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          huge-vmap
+#         Kconfig:       HAVE_ARCH_HUGE_VMAP
+#         description:   arch supports the arch_vmap_pud_supported() and arch_vmap_pmd_supported() VM APIs
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: | TODO |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: | TODO |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: | TODO |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: | TODO |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/vm/ioremap_prot/arch-support.txt b/Documentation/features/vm/ioremap_prot/arch-support.txt
new file mode 100644
index 000000000..c0a2d8f56
--- /dev/null
+++ b/Documentation/features/vm/ioremap_prot/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          ioremap_prot
+#         Kconfig:       HAVE_IOREMAP_PROT
+#         description:   arch has ioremap_prot()
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: | TODO |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ok  |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/vm/pte_special/arch-support.txt b/Documentation/features/vm/pte_special/arch-support.txt
new file mode 100644
index 000000000..3f777f8b6
--- /dev/null
+++ b/Documentation/features/vm/pte_special/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          pte_special
+#         Kconfig:       ARCH_HAS_PTE_SPECIAL
+#         description:   arch supports the pte_special()/pte_mkspecial() VM APIs
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: |  ok  |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ok  |
+    |       sparc: |  ok  |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------