Commit 4965f566 authored by T Makphaibulchoke's avatar T Makphaibulchoke Committed by Linus Torvalds
Browse files

kernel/resource.c: fix stack overflow in __reserve_region_with_split() 



Using a recursive call add a non-conflicting region in
__reserve_region_with_split() could result in a stack overflow in the case
that the recursive calls are too deep.  Convert the recursive calls to an
iterative loop to avoid the problem.

Tested on a machine containing 135 regions.  The kernel no longer panicked
with stack overflow.

Also tested with code arbitrarily adding regions with no conflict,
embedding two consecutive conflicts and embedding two non-consecutive
conflicts.

Signed-off-by: default avatarT Makphaibulchoke <tmac@hp.com>
Reviewed-by: default avatarRam Pai <linuxram@us.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@gmail.com>
Cc: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c99b6841

kernel/resource.c

+38 −12
Original line number Diff line number Diff line
@@ -763,6 +763,7 @@ static void __init __reserve_region_with_split(struct resource *root, 
	struct resource *parent = root;

	struct resource *conflict;

	struct resource *res = kzalloc(sizeof(*res), GFP_ATOMIC);

	struct resource *next_res = NULL;



	if (!res)

		return;
@@ -772,21 +773,46 @@ static void __init __reserve_region_with_split(struct resource *root, 
	res->end = end;

	res->flags = IORESOURCE_BUSY;



	while (1) {



		conflict = __request_resource(parent, res);

	if (!conflict)

		return;

		if (!conflict) {

			if (!next_res)

				break;

			res = next_res;

			next_res = NULL;

			continue;

		}



	/* failed, split and try again */

		/* conflict covered whole area */

		if (conflict->start <= res->start &&

				conflict->end >= res->end) {

			kfree(res);

			WARN_ON(next_res);

			break;

		}



	/* conflict covered whole area */

	if (conflict->start <= start && conflict->end >= end)

		return;

		/* failed, split and try again */

		if (conflict->start > res->start) {

			end = res->end;

			res->end = conflict->start - 1;

			if (conflict->end < end) {

				next_res = kzalloc(sizeof(*next_res),

						GFP_ATOMIC);

				if (!next_res) {

					kfree(res);

					break;

				}

				next_res->name = name;

				next_res->start = conflict->end + 1;

				next_res->end = end;

				next_res->flags = IORESOURCE_BUSY;

			}

		} else {

			res->start = conflict->end + 1;

		}

	}



	if (conflict->start > start)

		__reserve_region_with_split(root, start, conflict->start-1, name);

	if (conflict->end < end)

		__reserve_region_with_split(root, conflict->end+1, end, name);

}



void __init reserve_region_with_split(struct resource *root,

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