fs: fix FAT name extraction

The long name apparently can be accumulated using multiple
13-byte slots.  Unfortunately we never checked how many we
can actually fit in the buffer we are reading to.

Signed-off-by: Patrick Wildt <patrick@blueri.se>

diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index e0c076763f57add116f93ef173317c27cda44fca..ac8913e71929b1a847d09fdc1d69552f72afc962 100644 (file)
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -821,6 +821,9 @@ static dir_entry *extract_vfat_name(fat_itr *itr)
 
                slot2str((dir_slot *)dent, buf, &idx);
 
+               if (n + idx >= sizeof(itr->l_name))
+                       return NULL;
+
                /* shift accumulated long-name up and copy new part in: */
                memmove(itr->l_name + idx, itr->l_name, n);
                memcpy(itr->l_name, buf, idx);