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, 137 insertions, 0 deletions

diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
new file mode 100644
index 000000000..916d4f2bf
--- /dev/null
+++ b/security/integrity/Kconfig
@@ -0,0 +1,137 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+config INTEGRITY
+	bool "Integrity subsystem"
+	depends on SECURITY
+	default y
+	help
+	  This option enables the integrity subsystem, which is comprised
+	  of a number of different components including the Integrity
+	  Measurement Architecture (IMA), Extended Verification Module
+	  (EVM), IMA-appraisal extension, digital signature verification
+	  extension and audit measurement log support.
+
+	  Each of these components can be enabled/disabled separately.
+	  Refer to the individual components for additional details.
+
+if INTEGRITY
+
+config INTEGRITY_SIGNATURE
+	bool "Digital signature verification using multiple keyrings"
+	default n
+	select KEYS
+	select SIGNATURE
+	help
+	  This option enables digital signature verification support
+	  using multiple keyrings. It defines separate keyrings for each
+	  of the different use cases - evm, ima, and modules.
+	  Different keyrings improves search performance, but also allow
+	  to "lock" certain keyring to prevent adding new keys.
+	  This is useful for evm and module keyrings, when keys are
+	  usually only added from initramfs.
+
+config INTEGRITY_ASYMMETRIC_KEYS
+	bool "Enable asymmetric keys support"
+	depends on INTEGRITY_SIGNATURE
+	default n
+	select ASYMMETRIC_KEY_TYPE
+	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
+	select CRYPTO
+	select CRYPTO_RSA
+	select X509_CERTIFICATE_PARSER
+	help
+	  This option enables digital signature verification using
+	  asymmetric keys.
+
+config INTEGRITY_TRUSTED_KEYRING
+	bool "Require all keys on the integrity keyrings be signed"
+	depends on SYSTEM_TRUSTED_KEYRING
+	depends on INTEGRITY_ASYMMETRIC_KEYS
+	default y
+	help
+	   This option requires that all keys added to the .ima and
+	   .evm keyrings be signed by a key on the system trusted
+	   keyring.
+
+config INTEGRITY_PLATFORM_KEYRING
+	bool "Provide keyring for platform/firmware trusted keys"
+	depends on INTEGRITY_ASYMMETRIC_KEYS
+	depends on SYSTEM_BLACKLIST_KEYRING
+	help
+	  Provide a separate, distinct keyring for platform trusted keys, which
+	  the kernel automatically populates during initialization from values
+	  provided by the platform for verifying the kexec'ed kerned image
+	  and, possibly, the initramfs signature.
+
+config INTEGRITY_MACHINE_KEYRING
+	bool "Provide a keyring to which Machine Owner Keys may be added"
+	depends on SECONDARY_TRUSTED_KEYRING
+	depends on INTEGRITY_ASYMMETRIC_KEYS
+	depends on SYSTEM_BLACKLIST_KEYRING
+	depends on LOAD_UEFI_KEYS || LOAD_PPC_KEYS
+	help
+	  If set, provide a keyring to which Machine Owner Keys (MOK) may
+	  be added. This keyring shall contain just MOK keys.  Unlike keys
+	  in the platform keyring, keys contained in the .machine keyring will
+	  be trusted within the kernel.
+
+config INTEGRITY_CA_MACHINE_KEYRING
+	bool "Enforce Machine Keyring CA Restrictions"
+	depends on INTEGRITY_MACHINE_KEYRING
+	default n
+	help
+	  The .machine keyring can be configured to enforce CA restriction
+	  on any key added to it.  By default no restrictions are in place
+	  and all Machine Owner Keys (MOK) are added to the machine keyring.
+	  If enabled only CA keys are added to the machine keyring, all
+	  other MOK keys load into the platform keyring.
+
+config INTEGRITY_CA_MACHINE_KEYRING_MAX
+	bool "Only CA keys without DigitialSignature usage set"
+	depends on INTEGRITY_CA_MACHINE_KEYRING
+	default n
+	help
+	  When selected, only load CA keys are loaded into the machine
+	  keyring that contain the CA bit set along with the keyCertSign
+	  Usage field.  Keys containing the digitialSignature Usage field
+	  will not be loaded. The remaining MOK keys are loaded into the
+	  .platform keyring.
+
+config LOAD_UEFI_KEYS
+	depends on INTEGRITY_PLATFORM_KEYRING
+	depends on EFI
+	def_bool y
+
+config LOAD_IPL_KEYS
+	depends on INTEGRITY_PLATFORM_KEYRING
+	depends on S390
+	def_bool y
+
+config LOAD_PPC_KEYS
+	bool "Enable loading of platform and blacklisted keys for POWER"
+	depends on INTEGRITY_PLATFORM_KEYRING
+	depends on PPC_SECURE_BOOT
+	default y
+	help
+	  Enable loading of keys to the .platform keyring and blacklisted
+	  hashes to the .blacklist keyring for powerpc based platforms.
+
+config INTEGRITY_AUDIT
+	bool "Enables integrity auditing support "
+	depends on AUDIT
+	default y
+	help
+	  In addition to enabling integrity auditing support, this
+	  option adds a kernel parameter 'integrity_audit', which
+	  controls the level of integrity auditing messages.
+	  0 - basic integrity auditing messages (default)
+	  1 - additional integrity auditing messages
+
+	  Additional informational integrity auditing messages would
+	  be enabled by specifying 'integrity_audit=1' on the kernel
+	  command line.
+
+source "security/integrity/ima/Kconfig"
+source "security/integrity/evm/Kconfig"
+
+endif   # if INTEGRITY