Patch "erofs: ensure that the post-EOF tails are all zeroed" has been added to the 5.4-stable tree

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

    erofs: ensure that the post-EOF tails are all zeroed

to the 5.4-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:
     erofs-ensure-that-the-post-eof-tails-are-all-zeroed.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From hsiangkao at linux.alibaba.com  Sat Sep  2 09:30:52 2023
From: Gao Xiang <hsiangkao at linux.alibaba.com>
Date: Thu, 31 Aug 2023 19:29:58 +0800
Subject: erofs: ensure that the post-EOF tails are all zeroed
To: stable at vger.kernel.org, Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: linux-erofs at lists.ozlabs.org, Gao Xiang <hsiangkao at linux.alibaba.com>, keltargw <keltar.gw at gmail.com>
Message-ID: <20230831112959.99884-6-hsiangkao at linux.alibaba.com>

From: Gao Xiang <hsiangkao at linux.alibaba.com>

commit e4c1cf523d820730a86cae2c6d55924833b6f7ac upstream.

This was accidentally fixed up in commit e4c1cf523d82 but we can't
take the full change due to other dependancy issues, so here is just
the actual bugfix that is needed.

[Background]

keltargw reported an issue [1] that with mmaped I/Os, sometimes the
tail of the last page (after file ends) is not filled with zeroes.

The root cause is that such tail page could be wrongly selected for
inplace I/Os so the zeroed part will then be filled with compressed
data instead of zeroes.

A simple fix is to avoid doing inplace I/Os for such tail parts,
actually that was already fixed upstream in commit e4c1cf523d82
("erofs: tidy up z_erofs_do_read_page()") by accident.

[1] https://lore.kernel.org/r/3ad8b469-25db-a297-21f9-75db2d6ad224@linux.alibaba.com

Reported-by: keltargw <keltar.gw at gmail.com>
Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 fs/erofs/zdata.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -639,6 +639,8 @@ hitted:
 	cur = end - min_t(erofs_off_t, offset + end - map->m_la, end);
 	if (!(map->m_flags & EROFS_MAP_MAPPED)) {
 		zero_user_segment(page, cur, end);
+		++spiltted;
+		tight = false;
 		goto next_part;
 	}
 


Patches currently in stable-queue which might be from hsiangkao at linux.alibaba.com are

queue-5.4/erofs-ensure-that-the-post-eof-tails-are-all-zeroed.patch