This is a note to let you know that I've just added the patch titled
ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-fix-seek_hole-seek_data-for-blocksize-pagesize.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From fcf5ea10992fbac3c7473a1db33d56a139333cd1 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Sat, 5 Aug 2017 17:43:24 -0400
Subject: ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize
From: Jan Kara <jack@xxxxxxx>
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 <agruenba@xxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/file.c | 3 +++
1 file changed, 3 insertions(+)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -469,6 +469,8 @@ static int ext4_find_unwritten_pgoff(str
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)
@@ -483,6 +485,7 @@ static int ext4_find_unwritten_pgoff(str
unlock_page(page);
goto out;
}
+next:
lastoff += bh->b_size;
bh = bh->b_this_page;
} while (bh != head);
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-4.9/ext4-fix-seek_hole-seek_data-for-blocksize-pagesize.patch