[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>

4 files changed, 24 insertions, 5 deletions

diff --git a/drivers/block/genhd.c b/drivers/block/genhd.c
index 43805e4d31e..47fd3659a06 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;
diff --git a/fs/char_dev.c b/fs/char_dev.c
index c1e3537909f..e82aac9cc2f 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -56,10 +56,21 @@ int get_chrdev_list(char *page)
 
         down(&chrdevs_lock);
         for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
-                for (cd = chrdevs[i]; cd; cd = cd->next)
+                for (cd = chrdevs[i]; cd; cd = cd->next) {
+                        /*
+                         * if the current name, plus the 5 extra characters
+                         * in the device line for this entry
+                         * would run us off the page, we're done
+                         */
+                        if ((len+strlen(cd->name) + 5) >= PAGE_SIZE)
+                                goto page_full;
+
+
                         len += sprintf(page+len, "%3d %s\n",
                                        cd->major, cd->name);
+                }
         }
+page_full:
         up(&chrdevs_lock);
 
         return len;
diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 63a9fbf1ac5..94b570ad037 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -451,7 +451,7 @@ static int devices_read_proc(char *page, char **start, off_t off,
                                  int count, int *eof, void *data)
 {
         int len = get_chrdev_list(page);
-        len += get_blkdev_list(page+len);
+        len += get_blkdev_list(page+len, len);
         return proc_calc_metrics(page, start, off, count, eof, len);
 }
 
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index af26dc718ef..01796c41c95 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -224,7 +224,7 @@ static inline void free_disk_stats(struct gendisk *disk)
 extern void disk_round_stats(struct gendisk *disk);
 
 /* drivers/block/genhd.c */
-extern int get_blkdev_list(char *);
+extern int get_blkdev_list(char *, int);
 extern void add_disk(struct gendisk *disk);
 extern void del_gendisk(struct gendisk *gp);
 extern void unlink_gendisk(struct gendisk *gp);