Squashfs: Compute expected length from inode size rather than block length

Previously in squashfs_readpage() when copying data into the page
cache, it used the length of the datablock read from the filesystem
(after decompression).  However, if the filesystem has been corrupted
this data block may be short, which will leave pages unfilled.

The fix for this is to compute the expected number of bytes to copy
from the inode size, and use this to detect if the block is short.

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Tested-by: Willy Tarreau <w@1wt.eu>
Cc: Анатолий Тросиненко <anatoly.trosinenko@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 15 deletions

diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index cce3060650ae..f1c1430ae721 100644
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -431,10 +431,9 @@ skip_page:
 }
 
 /* Read datablock stored packed inside a fragment (tail-end packed block) */
-static int squashfs_readpage_fragment(struct page *page)
+static int squashfs_readpage_fragment(struct page *page, int expected)
 {
 	struct inode *inode = page->mapping->host;
-	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
 	struct squashfs_cache_entry *buffer = squashfs_get_fragment(inode->i_sb,
 		squashfs_i(inode)->fragment_block,
 		squashfs_i(inode)->fragment_size);
@@ -445,23 +444,16 @@ static int squashfs_readpage_fragment(struct page *page)
 			squashfs_i(inode)->fragment_block,
 			squashfs_i(inode)->fragment_size);
 	else
-		squashfs_copy_cache(page, buffer, i_size_read(inode) &
-			(msblk->block_size - 1),
+		squashfs_copy_cache(page, buffer, expected,
 			squashfs_i(inode)->fragment_offset);
 
 	squashfs_cache_put(buffer);
 	return res;
 }
 
-static int squashfs_readpage_sparse(struct page *page, int index, int file_end)
+static int squashfs_readpage_sparse(struct page *page, int expected)
 {
-	struct inode *inode = page->mapping->host;
-	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
-	int bytes = index == file_end ?
-			(i_size_read(inode) & (msblk->block_size - 1)) :
-			 msblk->block_size;
-
-	squashfs_copy_cache(page, NULL, bytes, 0);
+	squashfs_copy_cache(page, NULL, expected, 0);
 	return 0;
 }
 
@@ -471,6 +463,9 @@ static int squashfs_readpage(struct file *file, struct page *page)
 	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
 	int index = page->index >> (msblk->block_log - PAGE_SHIFT);
 	int file_end = i_size_read(inode) >> msblk->block_log;
+	int expected = index == file_end ?
+			(i_size_read(inode) & (msblk->block_size - 1)) :
+			 msblk->block_size;
 	int res;
 	void *pageaddr;
 
@@ -489,11 +484,11 @@ static int squashfs_readpage(struct file *file, struct page *page)
 			goto error_out;
 
 		if (bsize == 0)
-			res = squashfs_readpage_sparse(page, index, file_end);
+			res = squashfs_readpage_sparse(page, expected);
 		else
-			res = squashfs_readpage_block(page, block, bsize);
+			res = squashfs_readpage_block(page, block, bsize, expected);
 	} else
-		res = squashfs_readpage_fragment(page);
+		res = squashfs_readpage_fragment(page, expected);
 
 	if (!res)
 		return 0;