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, 56 insertions, 0 deletions

diff --git a/net/wireless/Makefile b/net/wireless/Makefile
new file mode 100644
index 000000000..a77fd5ba6
--- /dev/null
+++ b/net/wireless/Makefile
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_CFG80211) += cfg80211.o
+obj-y += tests/
+
+obj-$(CONFIG_WEXT_CORE) += wext-core.o
+obj-$(CONFIG_WEXT_PROC) += wext-proc.o
+obj-$(CONFIG_WEXT_PRIV) += wext-priv.o
+
+cfg80211-y += core.o sysfs.o radiotap.o util.o reg.o scan.o nl80211.o
+cfg80211-y += mlme.o ibss.o sme.o chan.o ethtool.o mesh.o ap.o trace.o ocb.o
+cfg80211-y += michael-mic.o pmsr.o
+cfg80211-$(CONFIG_OF) += of.o
+cfg80211-$(CONFIG_CFG80211_DEBUGFS) += debugfs.o
+cfg80211-$(CONFIG_CFG80211_WEXT) += wext-compat.o wext-sme.o
+
+CFLAGS_trace.o := -I$(src)
+
+cfg80211-$(CONFIG_CFG80211_USE_KERNEL_REGDB_KEYS) += shipped-certs.o
+ifneq ($(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR),)
+cfg80211-y += extra-certs.o
+endif
+
+$(obj)/shipped-certs.c: $(sort $(wildcard $(src)/certs/*.hex))
+	@$(kecho) "  GEN     $@"
+	$(Q)(echo '#include "reg.h"'; \
+	  echo 'const u8 shipped_regdb_certs[] = {'; \
+	  echo | cat - $^ ; \
+	  echo '};'; \
+	  echo 'unsigned int shipped_regdb_certs_len = sizeof(shipped_regdb_certs);'; \
+	 ) > $@
+
+$(obj)/extra-certs.c: $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR) \
+		      $(sort $(wildcard $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR)/*.x509))
+	@$(kecho) "  GEN     $@"
+	$(Q)(set -e; \
+	  allf=""; \
+	  for f in $^ ; do \
+	      test -f $$f || continue;\
+	      # similar to hexdump -v -e '1/1 "0x%.2x," "\n"' \
+	      thisf=$$(od -An -v -tx1 < $$f | \
+	                   sed -e 's/ /\n/g' | \
+	                   sed -e 's/^[0-9a-f]\+$$/\0/;t;d' | \
+	                   sed -e 's/^/0x/;s/$$/,/'); \
+	      # file should not be empty - maybe command substitution failed? \
+	      test ! -z "$$thisf";\
+	      allf=$$allf$$thisf;\
+	  done; \
+	  ( \
+	      echo '#include "reg.h"'; \
+	      echo 'const u8 extra_regdb_certs[] = {'; \
+	      echo "$$allf"; \
+	      echo '};'; \
+	      echo 'unsigned int extra_regdb_certs_len = sizeof(extra_regdb_certs);'; \
+	  ) > $@)
+
+clean-files += shipped-certs.c extra-certs.c