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: T Makphaibulchoke <tmac@hp.com>
Reviewed-by: Ram Pai <linuxram@us.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@gmail.com>
Cc: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/resource.c b/kernel/resource.c
index 34d45886ee8429acc7197c8ceaca18ef215fb2ae..73f35d4b30b9d22e727265f9ff06cd6250a88a36 100644 (file)
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -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;
 
-       conflict = __request_resource(parent, res);
-       if (!conflict)
-               return;
+       while (1) {
 
-       /* failed, split and try again */
-       kfree(res);
+               conflict = __request_resource(parent, res);
+               if (!conflict) {
+                       if (!next_res)
+                               break;
+                       res = next_res;
+                       next_res = NULL;
+                       continue;
+               }
 
-       /* conflict covered whole area */
-       if (conflict->start <= start && conflict->end >= end)
-               return;
+               /* conflict covered whole area */
+               if (conflict->start <= res->start &&
+                               conflict->end >= res->end) {
+                       kfree(res);
+                       WARN_ON(next_res);
+                       break;
+               }
+
+               /* 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,