This is a note to let you know that I've just added the patch titled
ext4: fix data races when using cached status extents
to the 6.2-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-data-races-when-using-cached-status-extents.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 492888df0c7b42fc0843631168b0021bc4caee84 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Thu, 4 May 2023 14:55:24 +0200
Subject: ext4: fix data races when using cached status extents
From: Jan Kara <jack@xxxxxxx>
commit 492888df0c7b42fc0843631168b0021bc4caee84 upstream.
When using cached extent stored in extent status tree in tree->cache_es
another process holding ei->i_es_lock for reading can be racing with us
setting new value of tree->cache_es. If the compiler would decide to
refetch tree->cache_es at an unfortunate moment, it could result in a
bogus in_range() check. Fix the possible race by using READ_ONCE() when
using tree->cache_es only under ei->i_es_lock for reading.
Cc: stable@xxxxxxxxxx
Reported-by: syzbot+4a03518df1e31b537066@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/000000000000d3b33905fa0fd4a6@xxxxxxxxxx
Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20230504125524.10802-1-jack@xxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/extents_status.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -267,14 +267,12 @@ static void __es_find_extent_range(struc
/* see if the extent has been cached */
es->es_lblk = es->es_len = es->es_pblk = 0;
- if (tree->cache_es) {
- es1 = tree->cache_es;
- if (in_range(lblk, es1->es_lblk, es1->es_len)) {
- es_debug("%u cached by [%u/%u) %llu %x\n",
- lblk, es1->es_lblk, es1->es_len,
- ext4_es_pblock(es1), ext4_es_status(es1));
- goto out;
- }
+ es1 = READ_ONCE(tree->cache_es);
+ if (es1 && in_range(lblk, es1->es_lblk, es1->es_len)) {
+ es_debug("%u cached by [%u/%u) %llu %x\n",
+ lblk, es1->es_lblk, es1->es_len,
+ ext4_es_pblock(es1), ext4_es_status(es1));
+ goto out;
}
es1 = __es_tree_search(&tree->root, lblk);
@@ -293,7 +291,7 @@ out:
}
if (es1 && matching_fn(es1)) {
- tree->cache_es = es1;
+ WRITE_ONCE(tree->cache_es, es1);
es->es_lblk = es1->es_lblk;
es->es_len = es1->es_len;
es->es_pblk = es1->es_pblk;
@@ -931,14 +929,12 @@ int ext4_es_lookup_extent(struct inode *
/* find extent in cache firstly */
es->es_lblk = es->es_len = es->es_pblk = 0;
- if (tree->cache_es) {
- es1 = tree->cache_es;
- if (in_range(lblk, es1->es_lblk, es1->es_len)) {
- es_debug("%u cached by [%u/%u)\n",
- lblk, es1->es_lblk, es1->es_len);
- found = 1;
- goto out;
- }
+ es1 = READ_ONCE(tree->cache_es);
+ if (es1 && in_range(lblk, es1->es_lblk, es1->es_len)) {
+ es_debug("%u cached by [%u/%u)\n",
+ lblk, es1->es_lblk, es1->es_len);
+ found = 1;
+ goto out;
}
node = tree->root.rb_node;
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-6.2/inotify-avoid-reporting-event-with-invalid-wd.patch
queue-6.2/ext4-fix-warning-in-mb_find_extent.patch
queue-6.2/ext4-avoid-deadlock-in-fs-reclaim-with-page-writeback.patch
queue-6.2/writeback-fix-call-of-incorrect-macro.patch
queue-6.2/ext4-check-iomap-type-only-if-ext4_iomap_begin-does-not-fail.patch
queue-6.2/ext4-fix-lockdep-warning-when-enabling-mmp.patch
queue-6.2/ext4-fix-data-races-when-using-cached-status-extents.patch
