linux-kernel - [RFC 1/1] fsnotify: next_i is freed during fsnotify_unmount

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Message-Id: <1412808434-36030-2-git-send-email-jerry.hoemann@hp.com>
Date:	Wed,  8 Oct 2014 16:47:14 -0600
From:	Jerry Hoemann <jerry.hoemann@...com>
To:	akpm@...ux-foundation.org, jeffrey.t.kirsher@...el.com,
	kenhelias@...email.de
Cc:	linux-kernel@...r.kernel.org, tmak@...com,
	Jerry Hoemann <jerry.hoemann@...com>
Subject: [RFC 1/1] fsnotify: next_i is freed during fsnotify_unmount_inodes.

During list_for_each_entry_safe, next_i is becoming free causing
the loop to never terminate.  Advance next_i in those cases where
__iget is not done.

Signed-off-by: Jerry Hoemann <jerry.hoemann@...com>
---
 fs/notify/inode_mark.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index 9ce0622..e849714 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -288,20 +288,25 @@ void fsnotify_unmount_inodes(struct list_head *list)
 		spin_unlock(&inode->i_lock);
 
 		/* In case the dropping of a reference would nuke next_i. */
-		if ((&next_i->i_sb_list != list) &&
-		    atomic_read(&next_i->i_count)) {
+		while (&next_i->i_sb_list != list) {
 			spin_lock(&next_i->i_lock);
-			if (!(next_i->i_state & (I_FREEING | I_WILL_FREE))) {
+			if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
+						atomic_read(&next_i->i_count)) {
 				__iget(next_i);
 				need_iput = next_i;
+				spin_unlock(&next_i->i_lock);
+				break;
 			}
 			spin_unlock(&next_i->i_lock);
+			next_i = list_entry(next_i->i_sb_list.next,
+						struct inode, i_sb_list);
 		}
 
 		/*
-		 * We can safely drop inode_sb_list_lock here because we hold
-		 * references on both inode and next_i.  Also no new inodes
-		 * will be added since the umount has begun.
+		 * We can safely drop inode_sb_list_lock here because either
+		 * we actually hold references on both inode and next_i or
+		 * end of list.  Also no new inodes will be added since the
+		 * umount has begun.
 		 */
 		spin_unlock(&inode_sb_list_lock);
 
-- 
1.7.11.3

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