Commit 8c40397f authored Nov 11, 2019 by Thomas Gleixner

x86/ptrace: Prevent truncation of bitmap size



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>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>

parent 31f4f5b4

arch/x86/kernel/ptrace.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -697,7 +697,7 @@ static int ptrace_set_debugreg(struct task_struct *tsk, int n,
		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,

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