[PATCH 3.16 38/47] udf: Fix incorrect final NOT_ALLOCATED (hole) extent length

Ben Hutchings
2019-10-25T18:07:27Z

From: "Steven J. Magnani" <steve.magnani@digidescorp.com>

commit fa33cdbf3eceb0206a4f844fe91aeebcf6ff2b7a upstream.

In some cases, using the 'truncate' command to extend a UDF file results
in a mismatch between the length of the file's extents (specifically, due
to incorrect length of the final NOT_ALLOCATED extent) and the information
(file) length. The discrepancy can prevent other operating systems
(i.e., Windows 10) from opening the file.

Two particular errors have been observed when extending a file:

1. The final extent is larger than it should be, having been rounded up
to a multiple of the block size.

B. The final extent is not shorter than it should be, due to not having
been updated when the file's information length was increased.

[JK: simplified udf_do_extend_final_block(), fixed up some types]

Fixes: 2c948b3f86e5 ("udf: Avoid IO in udf_clear_inode")
Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
Link: https://lore.kernel.org/r/1561948775-5878-1-git-send-email-steve@digidescorp.com
Signed-off-by: Jan Kara <jack@suse.cz>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/udf/inode.c | 93 ++++++++++++++++++++++++++++++++------------------
1 file changed, 60 insertions(+), 33 deletions(-)

--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -482,13 +482,15 @@ static struct buffer_head *udf_getblk(st
return NULL;
}

-/* Extend the file by 'blocks' blocks, return the number of extents added */
+/* Extend the file with new blocks totaling 'new_block_bytes',
+ * return the number of extents added
+ */
static int udf_do_extend_file(struct inode *inode,
struct extent_position *last_pos,
struct kernel_long_ad *last_ext,
- sector_t blocks)
+ loff_t new_block_bytes)
{
- sector_t add;
+ uint32_t add;
int count = 0, fake = !(last_ext->extLength & UDF_EXTENT_LENGTH_MASK);
struct super_block *sb = inode->i_sb;
struct kernel_lb_addr prealloc_loc = {};
@@ -498,7 +500,7 @@ static int udf_do_extend_file(struct ino

/* The previous extent is fake and we should not extend by anything
* - there's nothing to do... */
- if (!blocks && fake)
+ if (!new_block_bytes && fake)
return 0;

iinfo = UDF_I(inode);
@@ -529,13 +531,12 @@ static int udf_do_extend_file(struct ino
/* Can we merge with the previous extent? */
if ((last_ext->extLength & UDF_EXTENT_FLAG_MASK) ==
EXT_NOT_RECORDED_NOT_ALLOCATED) {
- add = ((1 << 30) - sb->s_blocksize -
- (last_ext->extLength & UDF_EXTENT_LENGTH_MASK)) >>
- sb->s_blocksize_bits;
- if (add > blocks)
- add = blocks;
- blocks -= add;
- last_ext->extLength += add << sb->s_blocksize_bits;
+ add = (1 << 30) - sb->s_blocksize -
+ (last_ext->extLength & UDF_EXTENT_LENGTH_MASK);
+ if (add > new_block_bytes)
+ add = new_block_bytes;
+ new_block_bytes -= add;
+ last_ext->extLength += add;
}

if (fake) {
@@ -547,28 +548,27 @@ static int udf_do_extend_file(struct ino
last_ext->extLength, 1);

/* Managed to do everything necessary? */
- if (!blocks)
+ if (!new_block_bytes)
goto out;

/* All further extents will be NOT_RECORDED_NOT_ALLOCATED */
last_ext->extLocation.logicalBlockNum = 0;
last_ext->extLocation.partitionReferenceNum = 0;
- add = (1 << (30-sb->s_blocksize_bits)) - 1;
- last_ext->extLength = EXT_NOT_RECORDED_NOT_ALLOCATED |
- (add << sb->s_blocksize_bits);
+ add = (1 << 30) - sb->s_blocksize;
+ last_ext->extLength = EXT_NOT_RECORDED_NOT_ALLOCATED | add;

/* Create enough extents to cover the whole hole */
- while (blocks > add) {
- blocks -= add;
+ while (new_block_bytes > add) {
+ new_block_bytes -= add;
err = udf_add_aext(inode, last_pos, &last_ext->extLocation,
last_ext->extLength, 1);
if (err)
return err;
count++;
}
- if (blocks) {
+ if (new_block_bytes) {
last_ext->extLength = EXT_NOT_RECORDED_NOT_ALLOCATED |
- (blocks << sb->s_blocksize_bits);
+ new_block_bytes;
err = udf_add_aext(inode, last_pos, &last_ext->extLocation,
last_ext->extLength, 1);
if (err)
@@ -599,6 +599,24 @@ out:
return count;
}

+/* Extend the final block of the file to final_block_len bytes */
+static void udf_do_extend_final_block(struct inode *inode,
+ struct extent_position *last_pos,
+ struct kernel_long_ad *last_ext,
+ uint32_t final_block_len)
+{
+ struct super_block *sb = inode->i_sb;
+ uint32_t added_bytes;
+
+ added_bytes = final_block_len -
+ (last_ext->extLength & (sb->s_blocksize - 1));
+ last_ext->extLength += added_bytes;
+ UDF_I(inode)->i_lenExtents += added_bytes;
+
+ udf_write_aext(inode, last_pos, &last_ext->extLocation,
+ last_ext->extLength, 1);
+}
+
static int udf_extend_file(struct inode *inode, loff_t newsize)
{

@@ -608,10 +626,12 @@ static int udf_extend_file(struct inode
int8_t etype;
struct super_block *sb = inode->i_sb;
sector_t first_block = newsize >> sb->s_blocksize_bits, offset;
+ unsigned long partial_final_block;
int adsize;
struct udf_inode_info *iinfo = UDF_I(inode);
struct kernel_long_ad extent;
- int err;
+ int err = 0;
+ int within_final_block;

if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_SHORT)
adsize = sizeof(struct short_ad);
@@ -621,18 +641,8 @@ static int udf_extend_file(struct inode
BUG();

etype = inode_bmap(inode, first_block, &epos, &eloc, &elen, &offset);
+ within_final_block = (etype != -1);

- /* File has extent covering the new size (could happen when extending
- * inside a block)? */
- if (etype != -1)
- return 0;
- if (newsize & (sb->s_blocksize - 1))
- offset++;
- /* Extended file just to the boundary of the last file block? */
- if (offset == 0)
- return 0;
-
- /* Truncate is extending the file by 'offset' blocks */
if ((!epos.bh && epos.offset == udf_file_entry_alloc_offset(inode)) ||
(epos.bh && epos.offset == sizeof(struct allocExtDesc))) {
/* File has no extents at all or has empty last
@@ -646,7 +656,22 @@ static int udf_extend_file(struct inode
&extent.extLength, 0);
extent.extLength |= etype << 30;
}
- err = udf_do_extend_file(inode, &epos, &extent, offset);
+
+ partial_final_block = newsize & (sb->s_blocksize - 1);
+
+ /* File has extent covering the new size (could happen when extending
+ * inside a block)?
+ */
+ if (within_final_block) {
+ /* Extending file within the last file block */
+ udf_do_extend_final_block(inode, &epos, &extent,
+ partial_final_block);
+ } else {
+ loff_t add = ((loff_t)offset << sb->s_blocksize_bits) |
+ partial_final_block;
+ err = udf_do_extend_file(inode, &epos, &extent, add);
+ }
+
if (err < 0)
goto out;
err = 0;
@@ -751,6 +776,7 @@ static sector_t inode_getblk(struct inod
/* Are we beyond EOF? */
if (etype == -1) {
int ret;
+ loff_t hole_len;
isBeyondEOF = 1;
if (count) {
if (c)
@@ -766,7 +792,8 @@ static sector_t inode_getblk(struct inod
startnum = (offset > 0);
}
/* Create extents for the hole between EOF and offset */
- ret = udf_do_extend_file(inode, &prev_epos, laarr, offset);
+ hole_len = (loff_t)offset << inode->i_blkbits;
+ ret = udf_do_extend_file(inode, &prev_epos, laarr, hole_len);
if (ret < 0) {
brelse(prev_epos.bh);
brelse(cur_epos.bh);