sound: oss: off by one bug

The problem is that in the original code sound_nblocks could go up to 1024
which would be an array overflow.

This was found with a static checker and has been compile tested only.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

3 files changed, 13 insertions, 9 deletions

diff --git a/sound/oss/dev_table.c b/sound/oss/dev_table.c
index 08274c995d0..727bdb9ba2d 100644
--- a/sound/oss/dev_table.c
+++ b/sound/oss/dev_table.c
@@ -67,14 +67,15 @@ int sound_install_audiodrv(int vers, char *name, struct audio_driver *driver,
                 return -(EBUSY);
         }
         d = (struct audio_driver *) (sound_mem_blocks[sound_nblocks] = vmalloc(sizeof(struct audio_driver)));
-
-        if (sound_nblocks < 1024)
-                sound_nblocks++;
+        sound_nblocks++;
+        if (sound_nblocks >= MAX_MEM_BLOCKS)
+                sound_nblocks = MAX_MEM_BLOCKS - 1;
 
         op = (struct audio_operations *) (sound_mem_blocks[sound_nblocks] = vmalloc(sizeof(struct audio_operations)));
+        sound_nblocks++;
+        if (sound_nblocks >= MAX_MEM_BLOCKS)
+                sound_nblocks = MAX_MEM_BLOCKS - 1;
 
-        if (sound_nblocks < 1024)
-                sound_nblocks++;
         if (d == NULL || op == NULL) {
                 printk(KERN_ERR "Sound: Can't allocate driver for (%s)\n", name);
                 sound_unload_audiodev(num);
@@ -128,9 +129,10 @@ int sound_install_mixer(int vers, char *name, struct mixer_operations *driver,
            until you unload sound! */
            
         op = (struct mixer_operations *) (sound_mem_blocks[sound_nblocks] = vmalloc(sizeof(struct mixer_operations)));
+        sound_nblocks++;
+        if (sound_nblocks >= MAX_MEM_BLOCKS)
+                sound_nblocks = MAX_MEM_BLOCKS - 1;
 
-        if (sound_nblocks < 1024)
-                sound_nblocks++;
         if (op == NULL) {
                 printk(KERN_ERR "Sound: Can't allocate mixer driver for (%s)\n", name);
                 return -ENOMEM;
diff --git a/sound/oss/sound_config.h b/sound/oss/sound_config.h
index 55271fbe7f4..9d35c4c65b9 100644
--- a/sound/oss/sound_config.h
+++ b/sound/oss/sound_config.h
@@ -142,4 +142,6 @@ static inline int translate_mode(struct file *file)
 #define TIMER_ARMED     121234
 #define TIMER_NOT_ARMED 1
 
+#define MAX_MEM_BLOCKS 1024
+
 #endif
diff --git a/sound/oss/soundcard.c b/sound/oss/soundcard.c
index 61aaedae6b7..c6253094388 100644
--- a/sound/oss/soundcard.c
+++ b/sound/oss/soundcard.c
@@ -56,7 +56,7 @@
 /*
  * Table for permanently allocated memory (used when unloading the module)
  */
-void *          sound_mem_blocks[1024];
+void *          sound_mem_blocks[MAX_MEM_BLOCKS];
 int             sound_nblocks = 0;
 
 /* Persistent DMA buffers */
@@ -574,7 +574,7 @@ static int __init oss_init(void)
                                       NULL, "%s%d", dev_list[i].name, j);
         }
 
-        if (sound_nblocks >= 1024)
+        if (sound_nblocks >= MAX_MEM_BLOCKS - 1)
                 printk(KERN_ERR "Sound warning: Deallocation table was too small.\n");
         
         return 0;