ALSA: info - Check file position validity in common layer

Check the validity of the file position in the common info layer before
calling read or write callbacks in assumption that entry->size is set up
properly to indicate the max file size.

Removed the redundant checks from the callbacks as well.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 11 insertions, 3 deletions

diff --git a/sound/core/info.c b/sound/core/info.c
index ff968be81678..f90a6fd43fb4 100644
--- a/sound/core/info.c
+++ b/sound/core/info.c
@@ -232,10 +232,15 @@ static ssize_t snd_info_entry_read(struct file *file, char __user *buffer,
                         return -EFAULT;
                 break;
         case SNDRV_INFO_CONTENT_DATA:
-                if (entry->c.ops->read)
+                if (pos >= entry->size)
+                        return 0;
+                if (entry->c.ops->read) {
+                        size = entry->size - pos;
+                        size = min(count, size);
                         size = entry->c.ops->read(entry,
                                                   data->file_private_data,
-                                                  file, buffer, count, pos);
+                                                  file, buffer, size, pos);
+                }
                 break;
         }
         if ((ssize_t) size > 0)
@@ -282,10 +287,13 @@ static ssize_t snd_info_entry_write(struct file *file, const char __user *buffer
                 size = count;
                 break;
         case SNDRV_INFO_CONTENT_DATA:
-                if (entry->c.ops->write)
+                if (entry->c.ops->write && count > 0) {
+                        size_t maxsize = entry->size - pos;
+                        count = min(count, maxsize);
                         size = entry->c.ops->write(entry,
                                                    data->file_private_data,
                                                    file, buffer, count, pos);
+                }
                 break;
         }
         if ((ssize_t) size > 0)