From: "Luis Henriques (SUSE)" <luis.henriques@linux.dev>
To: Theodore Ts'o <tytso@mit.edu>, Andreas Dilger <adilger@dilger.ca>,
Zhang Yi <yi.zhang@huaweicloud.com>,
Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
"Luis Henriques (SUSE)" <luis.henriques@linux.dev>
Subject: [PATCH] ext4: fix infinite loop when replaying fast_commit
Date: Fri, 10 May 2024 12:52:52 +0100 [thread overview]
Message-ID: <20240510115252.11850-1-luis.henriques@linux.dev> (raw)
When doing fast_commit replay an infinite loop may occur due to an
uninitialized extent_status struct. ext4_ext_determine_insert_hole() does
not detect the replay and calls ext4_es_find_extent_range(), which will
return immediately without initializing the 'es' variable.
Because 'es' contains garbage, an integer overflow may happen causing an
infinite loop in this function, easily reproducible using fstest generic/039.
This commit fixes this issue by detecting the replay in function
ext4_ext_determine_insert_hole(). It also adds initialization code to the
error path in function ext4_es_find_extent_range().
Thanks to Zhang Yi, for figuring out the real problem!
Fixes: 8016e29f4362 ("ext4: fast commit recovery path")
Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>
---
Hi!
Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero
macro instead. I decided not to do so simply because I wasn't sure if
that would be safe, but I'm fine changing that if you think it is.
2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in
ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid
the extra change to ext4_ext_map_blocks(). '0' sounds like the right
value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.
And again thanks to Zhang Yi for pointing me the *real* problem!
fs/ext4/extents.c | 6 +++++-
fs/ext4/extents_status.c | 5 ++++-
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index e57054bdc5fd..b5bfcb6c18a0 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4052,6 +4052,9 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
ext4_lblk_t hole_start, len;
struct extent_status es;
+ if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+ return 0;
+
hole_start = lblk;
len = ext4_ext_find_hole(inode, path, &hole_start);
again:
@@ -4226,7 +4229,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
len = ext4_ext_determine_insert_hole(inode, path, map->m_lblk);
map->m_pblk = 0;
- map->m_len = min_t(unsigned int, map->m_len, len);
+ if (len > 0)
+ map->m_len = min_t(unsigned int, map->m_len, len);
goto out;
}
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 4a00e2f019d9..acb9616ca119 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -310,8 +310,11 @@ void ext4_es_find_extent_range(struct inode *inode,
ext4_lblk_t lblk, ext4_lblk_t end,
struct extent_status *es)
{
- if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+ if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
+ /* Initialize extent to zero */
+ es->es_lblk = es->es_len = es->es_pblk = 0;
return;
+ }
trace_ext4_es_find_extent_range_enter(inode, lblk);
next reply other threads:[~2024-05-10 11:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-10 11:52 Luis Henriques (SUSE) [this message]
2024-05-11 6:24 ` [PATCH] ext4: fix infinite loop when replaying fast_commit Zhang Yi
2024-05-14 13:04 ` Luis Henriques
2024-05-15 4:59 ` Zhang Yi
2024-05-15 8:28 ` Luis Henriques
2024-05-15 8:52 ` Zhang Yi
2024-05-15 9:13 ` Luis Henriques
2024-05-15 12:24 ` Zhang Yi
2024-05-12 16:44 ` Markus Elfring
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