ALSA: mixart: range checking proc file

commit b0cc58a25d04160d39a80e436847eaa2fbc5aa09 upstream.

The original code doesn't take into consideration that the value of
MIXART_BA0_SIZE - pos can be less than zero which would lead to a large
unsigned value for "count".

Also I moved the check that read size is a multiple of 4 bytes below
the code that adjusts "count".

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/sound/pci/mixart/mixart.c b/sound/pci/mixart/mixart.c
index 7e83131..62ebff5 100644 (file)
--- a/sound/pci/mixart/mixart.c
+++ b/sound/pci/mixart/mixart.c
@@ -1160,13 +1160,15 @@ static long snd_mixart_BA0_read(struct snd_info_entry *entry, void *file_private
                                unsigned long count, unsigned long pos)
 {
        struct mixart_mgr *mgr = entry->private_data;
+       unsigned long maxsize;
 
-       count = count & ~3; /* make sure the read size is a multiple of 4 bytes */
-       if(count <= 0)
+       if (pos >= MIXART_BA0_SIZE)
                return 0;
-       if(pos + count > MIXART_BA0_SIZE)
-               count = (long)(MIXART_BA0_SIZE - pos);
-       if(copy_to_user_fromio(buf, MIXART_MEM( mgr, pos ), count))
+       maxsize = MIXART_BA0_SIZE - pos;
+       if (count > maxsize)
+               count = maxsize;
+       count = count & ~3; /* make sure the read size is a multiple of 4 bytes */
+       if (copy_to_user_fromio(buf, MIXART_MEM(mgr, pos), count))
                return -EFAULT;
        return count;
 }
@@ -1179,13 +1181,15 @@ static long snd_mixart_BA1_read(struct snd_info_entry *entry, void *file_private
                                unsigned long count, unsigned long pos)
 {
        struct mixart_mgr *mgr = entry->private_data;
+       unsigned long maxsize;
 
-       count = count & ~3; /* make sure the read size is a multiple of 4 bytes */
-       if(count <= 0)
+       if (pos > MIXART_BA1_SIZE)
                return 0;
-       if(pos + count > MIXART_BA1_SIZE)
-               count = (long)(MIXART_BA1_SIZE - pos);
-       if(copy_to_user_fromio(buf, MIXART_REG( mgr, pos ), count))
+       maxsize = MIXART_BA1_SIZE - pos;
+       if (count > maxsize)
+               count = maxsize;
+       count = count & ~3; /* make sure the read size is a multiple of 4 bytes */
+       if (copy_to_user_fromio(buf, MIXART_REG(mgr, pos), count))
                return -EFAULT;
        return count;
 }