From: Jan Kara <[email protected]>
commit fcf5ea10992fbac3c7473a1db33d56a139333cd1 upstream.
ext4_find_unwritten_pgoff() does not properly handle a situation when
starting index is in the middle of a page and blocksize < pagesize. The
following command shows the bug on filesystem with 1k blocksize:
xfs_io -f -c "falloc 0 4k" \
-c "pwrite 1k 1k" \
-c "pwrite 3k 1k" \
-c "seek -a -r 0" foo
In this example, neither lseek(fd, 1024, SEEK_HOLE) nor lseek(fd, 2048,
SEEK_DATA) will return the correct result.
Fix the problem by neglecting buffers in a page before starting offset.
Reported-by: Andreas Gruenbacher <[email protected]>
Signed-off-by: Theodore Ts'o <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
CC: [email protected] # 3.8+
Signed-off-by: Willy Tarreau <[email protected]>
---
fs/ext4/file.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index ec9770f..d490d6e 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -382,6 +382,8 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
lastoff = page_offset(page);
bh = head = page_buffers(page);
do {
+ if (lastoff + bh->b_size <= startoff)
+ goto next;
if (buffer_uptodate(bh) ||
buffer_unwritten(bh)) {
if (whence == SEEK_DATA)
@@ -396,6 +398,7 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
unlock_page(page);
goto out;
}
+next:
lastoff += bh->b_size;
bh = bh->b_this_page;
} while (bh != head);
--
2.8.0.rc2.1.gbe9624a
