Tasks get their end of stack set to STACK_END_MAGIC with the aim to catch stack overruns. Currently this feature does not apply to init_task. This patch removes this restriction.
Note that a similar patch was posted by Prarit Bhargava [1] some time ago but was never merged. [1]: http://marc.info/?l=linux-kernel&m=127144305403241&w=2 Signed-off-by: Aaron Tomlin <atom...@redhat.com> --- arch/powerpc/mm/fault.c | 3 +-- arch/x86/mm/fault.c | 3 +-- include/linux/sched.h | 2 ++ init/main.c | 1 + kernel/fork.c | 12 +++++++++--- kernel/trace/trace_stack.c | 4 +--- 6 files changed, 15 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 51ab9e7..35d0760c 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -30,7 +30,6 @@ #include <linux/kprobes.h> #include <linux/kdebug.h> #include <linux/perf_event.h> -#include <linux/magic.h> #include <linux/ratelimit.h> #include <linux/context_tracking.h> @@ -538,7 +537,7 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) regs->nip); stackend = end_of_stack(current); - if (current != &init_task && *stackend != STACK_END_MAGIC) + if (*stackend != STACK_END_MAGIC) printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); die("Kernel access of bad area", regs, sig); diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index a241946..bc23a70 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -3,7 +3,6 @@ * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar */ -#include <linux/magic.h> /* STACK_END_MAGIC */ #include <linux/sched.h> /* test_thread_flag(), ... */ #include <linux/kdebug.h> /* oops_begin/end, ... */ #include <linux/module.h> /* search_exception_table */ @@ -710,7 +709,7 @@ no_context(struct pt_regs *regs, unsigned long error_code, show_fault_oops(regs, error_code, address); stackend = end_of_stack(tsk); - if (tsk != &init_task && *stackend != STACK_END_MAGIC) + if (*stackend != STACK_END_MAGIC) printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); tsk->thread.cr2 = address; diff --git a/include/linux/sched.h b/include/linux/sched.h index 5c2c885..4dee9d7 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -57,6 +57,7 @@ struct sched_param { #include <linux/llist.h> #include <linux/uidgid.h> #include <linux/gfp.h> +#include <linux/magic.h> #include <asm/processor.h> @@ -2636,6 +2637,7 @@ static inline unsigned long stack_not_used(struct task_struct *p) return (unsigned long)n - (unsigned long)end_of_stack(p); } #endif +extern void task_stack_end_magic(struct task_struct *tsk); /* set thread flags in other task's structures * - see asm/thread_info.h for TIF_xxxx flags available diff --git a/init/main.c b/init/main.c index bb1aed9..bcdabf3a 100644 --- a/init/main.c +++ b/init/main.c @@ -508,6 +508,7 @@ asmlinkage __visible void __init start_kernel(void) * lockdep hash: */ lockdep_init(); + task_stack_end_magic(&init_task); smp_setup_processor_id(); debug_objects_early_init(); diff --git a/kernel/fork.c b/kernel/fork.c index 0cf9cdb..67cb1e3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -294,11 +294,18 @@ int __weak arch_dup_task_struct(struct task_struct *dst, return 0; } +void task_stack_end_magic(struct task_struct *tsk) +{ + unsigned long *stackend; + + stackend = end_of_stack(tsk); + *stackend = STACK_END_MAGIC; /* for overflow detection */ +} + static struct task_struct *dup_task_struct(struct task_struct *orig) { struct task_struct *tsk; struct thread_info *ti; - unsigned long *stackend; int node = tsk_fork_get_node(orig); int err; @@ -328,8 +335,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig) setup_thread_stack(tsk, orig); clear_user_return_notifier(tsk); clear_tsk_need_resched(tsk); - stackend = end_of_stack(tsk); - *stackend = STACK_END_MAGIC; /* for overflow detection */ + task_stack_end_magic(tsk); #ifdef CONFIG_CC_STACKPROTECTOR tsk->stack_canary = get_random_int(); diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index 8a4e5cb..1636e41 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -13,7 +13,6 @@ #include <linux/sysctl.h> #include <linux/init.h> #include <linux/fs.h> -#include <linux/magic.h> #include <asm/setup.h> @@ -171,8 +170,7 @@ check_stack(unsigned long ip, unsigned long *stack) i++; } - if ((current != &init_task && - *(end_of_stack(current)) != STACK_END_MAGIC)) { + if (*end_of_stack(current) != STACK_END_MAGIC) { print_max_stack(); BUG(); } -- 1.9.3 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
