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, 117 insertions, 0 deletions

diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
new file mode 100644
index 000000000..a110a6cd8
--- /dev/null
+++ b/security/ipe/Kconfig
@@ -0,0 +1,117 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Integrity Policy Enforcement (IPE) configuration
+#
+
+menuconfig SECURITY_IPE
+	bool "Integrity Policy Enforcement (IPE)"
+	depends on SECURITY && SECURITYFS && AUDIT && AUDITSYSCALL
+	select CRYPTO_LIB_SHA256
+	select PKCS7_MESSAGE_PARSER
+	select SYSTEM_DATA_VERIFICATION
+	select IPE_PROP_DM_VERITY if DM_VERITY
+	select IPE_PROP_DM_VERITY_SIGNATURE if DM_VERITY && DM_VERITY_VERIFY_ROOTHASH_SIG
+	select IPE_PROP_FS_VERITY if FS_VERITY
+	select IPE_PROP_FS_VERITY_BUILTIN_SIG if FS_VERITY && FS_VERITY_BUILTIN_SIGNATURES
+	help
+	  This option enables the Integrity Policy Enforcement LSM
+	  allowing users to define a policy to enforce a trust-based access
+	  control. A key feature of IPE is a customizable policy to allow
+	  admins to reconfigure trust requirements on the fly.
+
+	  If unsure, answer N.
+
+if SECURITY_IPE
+config IPE_BOOT_POLICY
+	string "Integrity policy to apply on system startup"
+	help
+	  This option specifies a filepath to an IPE policy that is compiled
+	  into the kernel. This policy will be enforced until a policy update
+	  is deployed via the $securityfs/ipe/policies/$policy_name/active
+	  interface.
+
+	  If unsure, leave blank.
+
+config IPE_POLICY_SIG_SECONDARY_KEYRING
+	bool "IPE policy update verification with secondary keyring"
+	default y
+	depends on SECONDARY_TRUSTED_KEYRING
+	help
+	  Also allow the secondary trusted keyring to verify IPE policy
+	  updates.
+
+	  If unsure, answer Y.
+
+config IPE_POLICY_SIG_PLATFORM_KEYRING
+	bool "IPE policy update verification with platform keyring"
+	default y
+	depends on INTEGRITY_PLATFORM_KEYRING
+	help
+	  Also allow the platform keyring to verify IPE policy updates.
+
+	  If unsure, answer Y.
+
+menu "IPE Trust Providers"
+
+config IPE_PROP_DM_VERITY
+	bool "Enable support for dm-verity based on root hash"
+	depends on DM_VERITY
+	help
+	  This option enables the 'dmverity_roothash' property within IPE
+	  policies. The property evaluates to TRUE when a file from a dm-verity
+	  volume is evaluated, and the volume's root hash matches the value
+	  supplied in the policy.
+
+config IPE_PROP_DM_VERITY_SIGNATURE
+	bool "Enable support for dm-verity based on root hash signature"
+	depends on DM_VERITY && DM_VERITY_VERIFY_ROOTHASH_SIG
+	help
+	  This option enables the 'dmverity_signature' property within IPE
+	  policies. The property evaluates to TRUE when a file from a dm-verity
+	  volume, which has been mounted with a valid signed root hash,
+	  is evaluated.
+
+	  If unsure, answer Y.
+
+config IPE_PROP_FS_VERITY
+	bool "Enable support for fs-verity based on file digest"
+	depends on FS_VERITY
+	help
+	  This option enables the 'fsverity_digest' property within IPE
+	  policies. The property evaluates to TRUE when a file is fsverity
+	  enabled and its digest matches the supplied digest value in the
+	  policy.
+
+	  if unsure, answer Y.
+
+config IPE_PROP_FS_VERITY_BUILTIN_SIG
+	bool "Enable support for fs-verity based on builtin signature"
+	depends on FS_VERITY && FS_VERITY_BUILTIN_SIGNATURES
+	help
+	  This option enables the 'fsverity_signature' property within IPE
+	  policies. The property evaluates to TRUE when a file is fsverity
+	  enabled and it has a valid builtin signature whose signing cert
+	  is in the .fs-verity keyring.
+
+	  if unsure, answer Y.
+
+endmenu
+
+config SECURITY_IPE_KUNIT_TEST
+	bool "Build KUnit tests for IPE" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the IPE KUnit tests.
+
+	  KUnit tests run during boot and output the results to the debug log
+	  in TAP format (https://testanything.org/). Only useful for kernel devs
+	  running KUnit test harness and are not for inclusion into a
+	  production build.
+
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
+endif