udf: Fix file corruption when appending just after end of preallocated extent

When we append new block just after the end of preallocated extent, the
code in inode_getblk() wrongly determined we're going to use the
preallocated extent which resulted in adding block into a wrong logical
offset in the file. Sequence like this manifests it:

xfs_io -f -c "pwrite 0x2cacf 0xd122" -c "truncate 0x2dd6f" \
  -c "pwrite 0x27fd9 0x69a9" -c "pwrite 0x32981 0x7244" <file>

The code that determined the use of preallocated extent is actually
stale because udf_do_extend_file() does not create preallocation anymore
so after calling that function we are sure there's no usable
preallocation. Just remove the faulty condition.

CC: stable@vger.kernel.org
Fixes: 16d055656814 ("udf: Discard preallocation before extending file with a hole")
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 356e15d..51deada 100644 (file)
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -742,19 +742,17 @@ static int inode_getblk(struct inode *inode, struct udf_map_rq *map)
                c = 0;
                offset = 0;
                count += ret;
-               /* We are not covered by a preallocated extent? */
-               if ((laarr[0].extLength & UDF_EXTENT_FLAG_MASK) !=
-                                               EXT_NOT_RECORDED_ALLOCATED) {
-                       /* Is there any real extent? - otherwise we overwrite
-                        * the fake one... */
-                       if (count)
-                               c = !c;
-                       laarr[c].extLength = EXT_NOT_RECORDED_NOT_ALLOCATED |
-                               inode->i_sb->s_blocksize;
-                       memset(&laarr[c].extLocation, 0x00,
-                               sizeof(struct kernel_lb_addr));
-                       count++;
-               }
+               /*
+                * Is there any real extent? - otherwise we overwrite the fake
+                * one...
+                */
+               if (count)
+                       c = !c;
+               laarr[c].extLength = EXT_NOT_RECORDED_NOT_ALLOCATED |
+                       inode->i_sb->s_blocksize;
+               memset(&laarr[c].extLocation, 0x00,
+                       sizeof(struct kernel_lb_addr));
+               count++;
                endnum = c + 1;
                lastblock = 1;
        } else {