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/trace/events/task.h | 99 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 99 insertions(+) create mode 100644 include/trace/events/task.h (limited to 'include/trace/events/task.h') diff --git a/include/trace/events/task.h b/include/trace/events/task.h new file mode 100644 index 000000000..b9a129eb5 --- /dev/null +++ b/include/trace/events/task.h @@ -0,0 +1,99 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM task + +#if !defined(_TRACE_TASK_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_TASK_H +#include + +TRACE_EVENT(task_newtask, + + TP_PROTO(struct task_struct *task, u64 clone_flags), + + TP_ARGS(task, clone_flags), + + TP_STRUCT__entry( + __field( pid_t, pid) + __array( char, comm, TASK_COMM_LEN) + __field( u64, clone_flags) + __field( short, oom_score_adj) + ), + + TP_fast_assign( + __entry->pid = task->pid; + memcpy(__entry->comm, task->comm, TASK_COMM_LEN); + __entry->clone_flags = clone_flags; + __entry->oom_score_adj = task->signal->oom_score_adj; + ), + + TP_printk("pid=%d comm=%s clone_flags=%llx oom_score_adj=%hd", + __entry->pid, __entry->comm, + __entry->clone_flags, __entry->oom_score_adj) +); + +TRACE_EVENT(task_rename, + + TP_PROTO(struct task_struct *task, const char *comm), + + TP_ARGS(task, comm), + + TP_STRUCT__entry( + __field( pid_t, pid) + __array( char, oldcomm, TASK_COMM_LEN) + __array( char, newcomm, TASK_COMM_LEN) + __field( short, oom_score_adj) + ), + + TP_fast_assign( + __entry->pid = task->pid; + memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN); + strscpy(entry->newcomm, comm, TASK_COMM_LEN); + __entry->oom_score_adj = task->signal->oom_score_adj; + ), + + TP_printk("pid=%d oldcomm=%s newcomm=%s oom_score_adj=%hd", + __entry->pid, __entry->oldcomm, + __entry->newcomm, __entry->oom_score_adj) +); + +/** + * task_prctl_unknown - called on unknown prctl() option + * @option: option passed + * @arg2: arg2 passed + * @arg3: arg3 passed + * @arg4: arg4 passed + * @arg5: arg5 passed + * + * Called on an unknown prctl() option. + */ +TRACE_EVENT(task_prctl_unknown, + + TP_PROTO(int option, unsigned long arg2, unsigned long arg3, + unsigned long arg4, unsigned long arg5), + + TP_ARGS(option, arg2, arg3, arg4, arg5), + + TP_STRUCT__entry( + __field( int, option) + __field( unsigned long, arg2) + __field( unsigned long, arg3) + __field( unsigned long, arg4) + __field( unsigned long, arg5) + ), + + TP_fast_assign( + __entry->option = option; + __entry->arg2 = arg2; + __entry->arg3 = arg3; + __entry->arg4 = arg4; + __entry->arg5 = arg5; + ), + + TP_printk("option=%d arg2=%ld arg3=%ld arg4=%ld arg5=%ld", + __entry->option, __entry->arg2, __entry->arg3, __entry->arg4, __entry->arg5) +); + +#endif + +/* This part must be outside protection */ +#include -- cgit v1.3.1