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 --- include/uapi/asm-generic/stat.h | 73 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 include/uapi/asm-generic/stat.h (limited to 'include/uapi/asm-generic/stat.h') diff --git a/include/uapi/asm-generic/stat.h b/include/uapi/asm-generic/stat.h new file mode 100644 index 000000000..0d962ecd1 --- /dev/null +++ b/include/uapi/asm-generic/stat.h @@ -0,0 +1,73 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef __ASM_GENERIC_STAT_H +#define __ASM_GENERIC_STAT_H + +/* + * Everybody gets this wrong and has to stick with it for all + * eternity. Hopefully, this version gets used by new architectures + * so they don't fall into the same traps. + * + * stat64 is copied from powerpc64, with explicit padding added. + * stat is the same structure layout on 64-bit, without the 'long long' + * types. + * + * By convention, 64 bit architectures use the stat interface, while + * 32 bit architectures use the stat64 interface. Note that we don't + * provide an __old_kernel_stat here, which new architecture should + * not have to start with. + */ + +#include + +#define STAT_HAVE_NSEC 1 + +struct stat { + unsigned long st_dev; /* Device. */ + unsigned long st_ino; /* File serial number. */ + unsigned int st_mode; /* File mode. */ + unsigned int st_nlink; /* Link count. */ + unsigned int st_uid; /* User ID of the file's owner. */ + unsigned int st_gid; /* Group ID of the file's group. */ + unsigned long st_rdev; /* Device number, if device. */ + unsigned long __pad1; + long st_size; /* Size of file, in bytes. */ + int st_blksize; /* Optimal block size for I/O. */ + int __pad2; + long st_blocks; /* Number 512-byte blocks allocated. */ + long st_atime; /* Time of last access. */ + unsigned long st_atime_nsec; + long st_mtime; /* Time of last modification. */ + unsigned long st_mtime_nsec; + long st_ctime; /* Time of last status change. */ + unsigned long st_ctime_nsec; + unsigned int __unused4; + unsigned int __unused5; +}; + +/* This matches struct stat64 in glibc2.1. Only used for 32 bit. */ +#if __BITS_PER_LONG != 64 || defined(__ARCH_WANT_STAT64) +struct stat64 { + unsigned long long st_dev; /* Device. */ + unsigned long long st_ino; /* File serial number. */ + unsigned int st_mode; /* File mode. */ + unsigned int st_nlink; /* Link count. */ + unsigned int st_uid; /* User ID of the file's owner. */ + unsigned int st_gid; /* Group ID of the file's group. */ + unsigned long long st_rdev; /* Device number, if device. */ + unsigned long long __pad1; + long long st_size; /* Size of file, in bytes. */ + int st_blksize; /* Optimal block size for I/O. */ + int __pad2; + long long st_blocks; /* Number 512-byte blocks allocated. */ + int st_atime; /* Time of last access. */ + unsigned int st_atime_nsec; + int st_mtime; /* Time of last modification. */ + unsigned int st_mtime_nsec; + int st_ctime; /* Time of last status change. */ + unsigned int st_ctime_nsec; + unsigned int __unused4; + unsigned int __unused5; +}; +#endif + +#endif /* __ASM_GENERIC_STAT_H */ -- cgit v1.3.1