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From:   Gabriel Krisman Bertazi <krisman@collabora.com>
To:     amir73il@gmail.com, jack@suse.com
Cc:     linux-api@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, khazhy@google.com,
        dhowells@redhat.com, david@fromorbit.com, tytso@mit.edu,
        djwong@kernel.org, repnop@google.com,
        Gabriel Krisman Bertazi <krisman@collabora.com>,
        kernel@collabora.com, Jan Kara <jack@suse.cz>
Subject: [PATCH v6 01/21] fsnotify: Don't insert unmergeable events in hashtable
Date:   Thu, 12 Aug 2021 17:39:50 -0400
Message-Id: <20210812214010.3197279-2-krisman@collabora.com>
In-Reply-To: <20210812214010.3197279-1-krisman@collabora.com>
References: <20210812214010.3197279-1-krisman@collabora.com>
MIME-Version: 1.0
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Some events, like the overflow event, are not mergeable, so they are not
hashed.  But, when failing inside fsnotify_add_event for lack of space,
fsnotify_add_event() still calls the insert hook, which adds the
overflow event to the merge list.  Add a check to prevent any kind of
unmergeable event to be inserted in the hashtable.

Fixes: 94e00d28a680 ("fsnotify: use hash table for faster events merge")
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

---
Changes since v2:
  - Do check for hashed events inside the insert hook (Amir)
---
 fs/notify/fanotify/fanotify.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 057abd2cf887..310246f8d3f1 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -702,6 +702,9 @@ static void fanotify_insert_event(struct fsnotify_group *group,
 
 	assert_spin_locked(&group->notification_lock);
 
+	if (!fanotify_is_hashed_event(event->mask))
+		return;
+
 	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
 		 group, event, bucket);
 
@@ -779,8 +782,7 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
 
 	fsn_event = &event->fse;
 	ret = fsnotify_add_event(group, fsn_event, fanotify_merge,
-				 fanotify_is_hashed_event(mask) ?
-				 fanotify_insert_event : NULL);
+				 fanotify_insert_event);
 	if (ret) {
 		/* Permission events shouldn't be merged */
 		BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
-- 
2.32.0