linux-kernel - [PATCH v2 2/7] fsnotify: pin both inode and vfsmount mark

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Message-Id: <1508920899-8115-3-git-send-email-mszeredi@redhat.com>
Date:   Wed, 25 Oct 2017 10:41:34 +0200
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
        Xiong Zhou <xzhou@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/7] fsnotify: pin both inode and vfsmount mark

We may fail to pin one of the marks in fsnotify_prepare_user_wait() when
dropping the srcu read lock, resulting in use after free at the next
iteration.

Solution is to store both marks in iter_info instead of just the one we'll
be sending the event for.

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Fixes: 9385a84d7e1f ("fsnotify: Pass fsnotify_iter_info into handle_event handler")
Cc: <stable@...r.kernel.org> # v4.12
---
 fs/notify/fsnotify.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 0c4583b61717..48ec61f4c4d5 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -336,6 +336,9 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 			vfsmount_group = vfsmount_mark->group;
 		}
 
+		iter_info.inode_mark = inode_mark;
+		iter_info.vfsmount_mark = vfsmount_mark;
+
 		if (inode_group && vfsmount_group) {
 			int cmp = fsnotify_compare_groups(inode_group,
 							  vfsmount_group);
@@ -348,9 +351,6 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 			}
 		}
 
-		iter_info.inode_mark = inode_mark;
-		iter_info.vfsmount_mark = vfsmount_mark;
-
 		ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask,
 				    data, data_is, cookie, file_name,
 				    &iter_info);
-- 
2.5.5