[patch 1/9] x86/ptrace: Prevent truncation of bitmap size

Thomas Gleixner
2019-11-06T20:56:48Z

The active() callback of the IO bitmap regset divides the IO bitmap size by
the word size (32/64 bit). As the I/O bitmap size is in bytes the active
check fails for bitmap sizes of 1-3 bytes on 32bit and 1-7 bytes on 64bit.

Use DIV_ROUND_UP() instead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/ptrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -697,7 +697,7 @@ static int ptrace_set_debugreg(struct ta
static int ioperm_active(struct task_struct *target,
const struct user_regset *regset)
{
- return target->thread.io_bitmap_max / regset->size;
+ return DIV_ROUND_UP(target->thread.io_bitmap_max, regset->size);
}

static int ioperm_get(struct task_struct *target,