[PATCH] add check to /proc/devices read routines

Patch to add check to get_chrdev_list and get_blkdev_list to prevent reads
of /proc/devices from spilling over the provided page if more than 4096
bytes of string data are generated from all the registered character and
block devices in a system

Signed-off-by: Neil Horman <nhorman@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/drivers/block/genhd.c b/drivers/block/genhd.c
index 43805e4..47fd365 100644
--- a/drivers/block/genhd.c
+++ b/drivers/block/genhd.c
@@ -40,7 +40,7 @@ static inline int major_to_index(int major)
 
 #ifdef CONFIG_PROC_FS
 /* get block device names in somewhat random order */
-int get_blkdev_list(char *p)
+int get_blkdev_list(char *p, int used)
 {
 	struct blk_major_name *n;
 	int i, len;
@@ -49,10 +49,18 @@ int get_blkdev_list(char *p)
 
 	down(&block_subsys_sem);
 	for (i = 0; i < ARRAY_SIZE(major_names); i++) {
-		for (n = major_names[i]; n; n = n->next)
+		for (n = major_names[i]; n; n = n->next) {
+			/*
+			 * If the curent string plus the 5 extra characters
+			 * in the line would run us off the page, then we're done
+			 */
+			if ((len + used + strlen(n->name) + 5) >= PAGE_SIZE)
+				goto page_full;
 			len += sprintf(p+len, "%3d %s\n",
 				       n->major, n->name);
+		}
 	}
+page_full:
 	up(&block_subsys_sem);
 
 	return len;