From 6b6751f7feba68d8f5c72b72cc69a1c5a625529c Mon Sep 17 00:00:00 2001 From: Ian Kent <raven@themaw.net> Date: Tue, 6 May 2014 12:50:06 -0700 Subject: [PATCH] autofs: fix lockref lookup autofs needs to be able to see private data dentry flags for its dentrys that are being created but not yet hashed and for its dentrys that have been rmdir()ed but not yet freed. It needs to do this so it can block processes in these states until a status has been returned to indicate the given operation is complete. It does this by keeping two lists, active and expring, of dentrys in this state and uses ->d_release() to keep them stable while it checks the reference count to determine if they should be used. But with the recent lockref changes dentrys being freed sometimes don't transition to a reference count of 0 before being freed so autofs can occassionally use a dentry that is invalid which can lead to a panic. Signed-off-by: Ian Kent <raven@themaw.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- fs/autofs4/root.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index 2caf36ac3e93..cc87c1abac97 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -179,7 +179,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry) spin_lock(&active->d_lock); /* Already gone? */ - if (!d_count(active)) + if ((int) d_count(active) <= 0) goto next; qstr = &active->d_name; @@ -230,7 +230,7 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry) spin_lock(&expiring->d_lock); - /* Bad luck, we've already been dentry_iput */ + /* We've already been dentry_iput or unlinked */ if (!expiring->d_inode) goto next; -- GitLab