From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults 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 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) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- Documentation/ABI/testing/sysfs-kernel-livepatch | 95 ++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-kernel-livepatch (limited to 'Documentation/ABI/testing/sysfs-kernel-livepatch') diff --git a/Documentation/ABI/testing/sysfs-kernel-livepatch b/Documentation/ABI/testing/sysfs-kernel-livepatch new file mode 100644 index 000000000..3c3f36b32 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-livepatch @@ -0,0 +1,95 @@ +What: /sys/kernel/livepatch +Date: Nov 2014 +KernelVersion: 3.19.0 +Contact: live-patching@vger.kernel.org +Description: + Interface for kernel live patching + + The /sys/kernel/livepatch directory contains subdirectories for + each loaded live patch module. + +What: /sys/kernel/livepatch/ +Date: Nov 2014 +KernelVersion: 3.19.0 +Contact: live-patching@vger.kernel.org +Description: + The patch directory contains subdirectories for each kernel + object (vmlinux or a module) in which it patched functions. + +What: /sys/kernel/livepatch//enabled +Date: Nov 2014 +KernelVersion: 3.19.0 +Contact: live-patching@vger.kernel.org +Description: + A writable attribute that indicates whether the patched + code is currently applied. Writing 0 will disable the patch + while writing 1 will re-enable the patch. + +What: /sys/kernel/livepatch//transition +Date: Feb 2017 +KernelVersion: 4.12.0 +Contact: live-patching@vger.kernel.org +Description: + An attribute which indicates whether the patch is currently in + transition. + +What: /sys/kernel/livepatch//force +Date: Nov 2017 +KernelVersion: 4.15.0 +Contact: live-patching@vger.kernel.org +Description: + A writable attribute that allows administrator to affect the + course of an existing transition. Writing 1 clears + TIF_PATCH_PENDING flag of all tasks and thus forces the tasks to + the patched or unpatched state. Administrator should not + use this feature without a clearance from a patch + distributor. Removal (rmmod) of patch modules is permanently + disabled when the feature is used. See + Documentation/livepatch/livepatch.rst for more information. + +What: /sys/kernel/livepatch//replace +Date: Jun 2024 +KernelVersion: 6.11.0 +Contact: live-patching@vger.kernel.org +Description: + An attribute which indicates whether the patch supports + atomic-replace. + +What: /sys/kernel/livepatch//stack_order +Date: Jan 2025 +KernelVersion: 6.14.0 +Description: + This attribute specifies the sequence in which live patch modules + are applied to the system. If multiple live patches modify the same + function, the implementation with the biggest 'stack_order' number + is used, unless a transition is currently in progress. + +What: /sys/kernel/livepatch// +Date: Nov 2014 +KernelVersion: 3.19.0 +Contact: live-patching@vger.kernel.org +Description: + The object directory contains subdirectories for each function + that is patched within the object. + +What: /sys/kernel/livepatch///patched +Date: August 2022 +KernelVersion: 6.1.0 +Contact: live-patching@vger.kernel.org +Description: + An attribute which indicates whether the object is currently + patched. + +What: /sys/kernel/livepatch/// +Date: Nov 2014 +KernelVersion: 3.19.0 +Contact: live-patching@vger.kernel.org +Description: + The function directory contains attributes regarding the + properties and state of the patched function. + + The directory name contains the patched function name and a + sympos number corresponding to the nth occurrence of the symbol + name in kallsyms for the patched object. + + There are currently no such attributes. -- cgit v1.3.1