udf: Fix memory corruption when fs mounted with noadinicb option

When UDF filesystem is mounted with noadinicb mount option, it
happens that we extend an empty directory with a block. A code in
udf_add_entry() didn't count with this possibility and used
uninitialized data leading to memory and filesystem corruption.
Add a check whether file already has some extents before operating
on them.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 47a6589e10b5..3d94bc1cfbaf 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -315,7 +315,7 @@ static struct fileIdentDesc *udf_add_entry(struct inode *dir,
         uint16_t liu;
         int block;
         kernel_lb_addr eloc;
-        uint32_t elen;
+        uint32_t elen = 0;
         sector_t offset;
         struct extent_position epos = {};
         struct udf_inode_info *dinfo;
@@ -406,7 +406,8 @@ static struct fileIdentDesc *udf_add_entry(struct inode *dir,
         }
 
 add:
-        if (dinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
+        /* Is there any extent whose size we need to round up? */
+        if (dinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB && elen) {
                 elen = (elen + sb->s_blocksize - 1) & ~(sb->s_blocksize - 1);
                 if (dinfo->i_alloc_type == ICBTAG_FLAG_AD_SHORT)
                         epos.offset -= sizeof(short_ad);