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Commit 01d553d0 authored by Amos Waterland's avatar Amos Waterland Committed by Linus Torvalds
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[PATCH] Chardev checking of overlapping ranges 



The code in __register_chrdev_region checks that if the driver wishing to
register has the same major as an existing driver the new minor range is
strictly less than the existing minor range.  However, it does not also
check that the new minor range is strictly greater than the existing minor
range.  That is, if driver X has registered with major=x and minor=0-3,
__register_chrdev_region will allow driver Y to register with major=x and
minor=1-4.

Signed-off-by: default avatarAmos Waterland <apw@us.ibm.com>
Cc: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f400e198

fs/char_dev.c

+23 −5
Original line number Diff line number Diff line
@@ -128,13 +128,31 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor, 


	for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)

		if ((*cp)->major > major ||

		    ((*cp)->major == major && (*cp)->baseminor >= baseminor))

		    ((*cp)->major == major &&

		     (((*cp)->baseminor >= baseminor) ||

		      ((*cp)->baseminor + (*cp)->minorct > baseminor))))

			break;

	if (*cp && (*cp)->major == major &&

	    (*cp)->baseminor < baseminor + minorct) {



	/* Check for overlapping minor ranges.  */

	if (*cp && (*cp)->major == major) {

		int old_min = (*cp)->baseminor;

		int old_max = (*cp)->baseminor + (*cp)->minorct - 1;

		int new_min = baseminor;

		int new_max = baseminor + minorct - 1;



		/* New driver overlaps from the left.  */

		if (new_max >= old_min && new_max <= old_max) {

			ret = -EBUSY;

			goto out;

		}



		/* New driver overlaps from the right.  */

		if (new_min <= old_max && new_min >= old_min) {

			ret = -EBUSY;

			goto out;

		}

	}



	cd->next = *cp;

	*cp = cd;

	mutex_unlock(&chrdevs_lock);