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Revision 9c603e53d380459fb62fec7cd085acb0b74ac18f authored by Linus Torvalds on 08 September 2012, 19:57:30 UTC, committed by Linus Torvalds on 28 September 2012, 19:13:46 UTC 
mtdchar: fix offset overflow detection
 
Sasha Levin has been running trinity in a KVM tools guest, and was able
to trigger the BUG_ON() at arch/x86/mm/pat.c:279 (verifying the range of
the memory type).  The call trace showed that it was mtdchar_mmap() that
created an invalid remap_pfn_range().

The problem is that mtdchar_mmap() does various really odd and subtle
things with the vma page offset etc, and uses the wrong types (and the
wrong overflow) detection for it.

For example, the page offset may well be 32-bit on a 32-bit
architecture, but after shifting it up by PAGE_SHIFT, we need to use a
potentially 64-bit resource_size_t to correctly hold the full value.

Also, we need to check that the vma length plus offset doesn't overflow
before we check that it is smaller than the length of the mtdmap region.

This fixes things up and tries to make the code a bit easier to read.

Reported-and-tested-by: Sasha Levin <levinsasha928@gmail.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Artem Bityutskiy <dedekind1@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: linux-mtd@lists.infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 6672d90
Raw File
task_work.c 
#include <linux/spinlock.h>
#include <linux/task_work.h>
#include <linux/tracehook.h>

int
task_work_add(struct task_struct *task, struct callback_head *twork, bool notify)
{
	struct callback_head *last, *first;
	unsigned long flags;

	/*
	 * Not inserting the new work if the task has already passed
	 * exit_task_work() is the responisbility of callers.
	 */
	raw_spin_lock_irqsave(&task->pi_lock, flags);
	last = task->task_works;
	first = last ? last->next : twork;
	twork->next = first;
	if (last)
		last->next = twork;
	task->task_works = twork;
	raw_spin_unlock_irqrestore(&task->pi_lock, flags);

	/* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
	if (notify)
		set_notify_resume(task);
	return 0;
}

struct callback_head *
task_work_cancel(struct task_struct *task, task_work_func_t func)
{
	unsigned long flags;
	struct callback_head *last, *res = NULL;

	raw_spin_lock_irqsave(&task->pi_lock, flags);
	last = task->task_works;
	if (last) {
		struct callback_head *q = last, *p = q->next;
		while (1) {
			if (p->func == func) {
				q->next = p->next;
				if (p == last)
					task->task_works = q == p ? NULL : q;
				res = p;
				break;
			}
			if (p == last)
				break;
			q = p;
			p = q->next;
		}
	}
	raw_spin_unlock_irqrestore(&task->pi_lock, flags);
	return res;
}

void task_work_run(void)
{
	struct task_struct *task = current;
	struct callback_head *p, *q;

	while (1) {
		raw_spin_lock_irq(&task->pi_lock);
		p = task->task_works;
		task->task_works = NULL;
		raw_spin_unlock_irq(&task->pi_lock);

		if (unlikely(!p))
			return;

		q = p->next; /* head */
		p->next = NULL; /* cut it */
		while (q) {
			p = q->next;
			q->func(q);
			q = p;
			cond_resched();
		}
	}
}
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