diff options
Diffstat (limited to 'kernel/stackleak.c')
| -rw-r--r-- | kernel/stackleak.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/kernel/stackleak.c b/kernel/stackleak.c index d5f684dc0a2d..ba346d46218f 100644 --- a/kernel/stackleak.c +++ b/kernel/stackleak.c @@ -73,6 +73,7 @@ late_initcall(stackleak_sysctls_init); static __always_inline void __stackleak_erase(void) { const unsigned long task_stack_low = stackleak_task_low_bound(current); + const unsigned long task_stack_high = stackleak_task_high_bound(current); unsigned long erase_low = current->lowest_stack; unsigned long erase_high; unsigned int poison_count = 0; @@ -93,14 +94,22 @@ static __always_inline void __stackleak_erase(void) #endif /* - * Now write the poison value to the kernel stack between 'erase_low' - * and 'erase_high'. We assume that the stack pointer doesn't change - * when we write poison. + * Write poison to the task's stack between 'erase_low' and + * 'erase_high'. + * + * If we're running on a different stack (e.g. an entry trampoline + * stack) we can erase everything below the pt_regs at the top of the + * task stack. + * + * If we're running on the task stack itself, we must not clobber any + * stack used by this function and its caller. We assume that this + * function has a fixed-size stack frame, and the current stack pointer + * doesn't change while we write poison. */ if (on_thread_stack()) erase_high = current_stack_pointer; else - erase_high = current_top_of_stack(); + erase_high = task_stack_high; while (erase_low < erase_high) { *(unsigned long *)erase_low = STACKLEAK_POISON; @@ -108,7 +117,7 @@ static __always_inline void __stackleak_erase(void) } /* Reset the 'lowest_stack' value for the next syscall */ - current->lowest_stack = current_top_of_stack() - THREAD_SIZE/64; + current->lowest_stack = task_stack_high; } asmlinkage void noinstr stackleak_erase(void) |