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[3.13.y.z,extended,stable] Patch "be careful with nd->inode in path_init() and follow_dotdot_rcu()" has been added to staging queue

Message ID 1412806455-31948-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Oct. 8, 2014, 10:14 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    be careful with nd->inode in path_init() and follow_dotdot_rcu()

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.9.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 6e3747f1c7b7b6d5627856d611cc697d1fe7296c Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 13 Sep 2014 21:59:43 -0400
Subject: be careful with nd->inode in path_init() and follow_dotdot_rcu()

commit 4023bfc9f351a7994fb6a7d515476c320f94a574 upstream.

in the former we simply check if dentry is still valid after picking
its ->d_inode; in the latter we fetch ->d_inode in the same places
where we fetch dentry and its ->d_seq, under the same checks.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 fs/namei.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--
1.9.1
diff mbox

Patch

diff --git a/fs/namei.c b/fs/namei.c
index aed3458..eaabb52 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1119,6 +1119,7 @@  static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,

 static int follow_dotdot_rcu(struct nameidata *nd)
 {
+	struct inode *inode = nd->inode;
 	if (!nd->root.mnt)
 		set_root_rcu(nd);

@@ -1132,6 +1133,7 @@  static int follow_dotdot_rcu(struct nameidata *nd)
 			struct dentry *parent = old->d_parent;
 			unsigned seq;

+			inode = parent->d_inode;
 			seq = read_seqcount_begin(&parent->d_seq);
 			if (read_seqcount_retry(&old->d_seq, nd->seq))
 				goto failed;
@@ -1141,6 +1143,7 @@  static int follow_dotdot_rcu(struct nameidata *nd)
 		}
 		if (!follow_up_rcu(&nd->path))
 			break;
+		inode = nd->path.dentry->d_inode;
 		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
 	}
 	while (d_mountpoint(nd->path.dentry)) {
@@ -1150,11 +1153,12 @@  static int follow_dotdot_rcu(struct nameidata *nd)
 			break;
 		nd->path.mnt = &mounted->mnt;
 		nd->path.dentry = mounted->mnt.mnt_root;
+		inode = nd->path.dentry->d_inode;
 		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
 		if (!read_seqretry(&mount_lock, nd->m_seq))
 			goto failed;
 	}
-	nd->inode = nd->path.dentry->d_inode;
+	nd->inode = inode;
 	return 0;

 failed:
@@ -1883,7 +1887,14 @@  static int path_init(int dfd, const char *name, unsigned int flags,
 	}

 	nd->inode = nd->path.dentry->d_inode;
-	return 0;
+	if (!(flags & LOOKUP_RCU))
+		return 0;
+	if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
+		return 0;
+	if (!(nd->flags & LOOKUP_ROOT))
+		nd->root.mnt = NULL;
+	rcu_read_unlock();
+	return -ECHILD;
 }

 static inline int lookup_last(struct nameidata *nd, struct path *path)