[PATCH] swsusp: avoid problems if there are too many pages to save

The following patch makes swsusp avoid problems during resume if there are
too many pages to save on suspend.  It adds a constant that allows us to
verify if we are going to save too many pages and implements the check
(this is done as early as we can tell that the check will trigger, which is
in swsusp_alloc()).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/power/power.h

@@ -9,6 +9,9 @@
 #define SUSPEND_CONSOLE	(MAX_NR_CONSOLES-1)
 #endif
 
+#define MAX_PBES	((PAGE_SIZE - sizeof(struct new_utsname) \
+			- 4 - 3*sizeof(unsigned long) - sizeof(int) \
+			- sizeof(void *)) / sizeof(swp_entry_t))
 
 struct swsusp_info {
 	struct new_utsname	uts;
@@ -18,7 +21,7 @@ struct swsusp_info {
 	unsigned long		image_pages;
 	unsigned long		pagedir_pages;
 	suspend_pagedir_t	* suspend_pagedir;
-	swp_entry_t		pagedir[768];
+	swp_entry_t		pagedir[MAX_PBES];
 } __attribute__((aligned(PAGE_SIZE)));
 
 

kernel/power/swsusp.c

@@ -931,6 +931,10 @@ static int swsusp_alloc(void)
 	if (!enough_swap())
 		return -ENOSPC;
 
+	if (MAX_PBES < nr_copy_pages / PBES_PER_PAGE +
+	    !!(nr_copy_pages % PBES_PER_PAGE))
+		return -ENOSPC;
+
 	if (!(pagedir_save = alloc_pagedir(nr_copy_pages))) {
 		printk(KERN_ERR "suspend: Allocating pagedir failed.\n");
 		return -ENOMEM;