From fb6e94be49cb8c1f1d73a38c3d55cd0726b1e06f Mon Sep 17 00:00:00 2001
From: Gao Xiang <hsiangkao@linux.alibaba.com>
Date: Thu, 31 Aug 2023 19:29:58 +0800
Subject: [PATCH] erofs: ensure that the post-EOF tails are all zeroed
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@gmail.com>
Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/erofs/zdata.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 361f3c29897e8..1b91ac5be9610 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -869,6 +869,8 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
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;
}
if (map->m_flags & EROFS_MAP_FRAGMENT) {
--
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