linux-kernel - [PATCH] fs/9p: Compare qid.path in v9fs_test

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Message-ID: <20170222000629.7995-1-tuomas@tuxera.com>
Date:   Wed, 22 Feb 2017 02:06:29 +0200
From:   Tuomas Tynkkynen <tuomas@...era.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>
CC:     <linux-fsdevel@...r.kernel.org>,
        Eric Van Hensbergen <ericvh@...il.com>,
        <v9fs-developer@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Tuomas Tynkkynen <tuomas@...era.com>, <stable@...r.kernel.org>
Subject: [PATCH] fs/9p: Compare qid.path in v9fs_test_inode

Commit fd2421f54423 ("fs/9p: When doing inode lookup compare qid details
and inode mode bits.") transformed v9fs_qid_iget() to use iget5_locked()
instead of iget_locked(). However, the test() callback is not checking
fid.path at all, which means that a lookup in the inode cache can now
accidentally locate a completely wrong inode from the same inode hash
bucket if the other fields (qid.type and qid.version) match.

Fixes: fd2421f54423 ("fs/9p: When doing inode lookup compare qid details and inode mode bits.")
Cc: stable@...r.kernel.org
Signed-off-by: Tuomas Tynkkynen <tuomas@...era.com>
---
Does this sound sensible? I have never reproduced the problem myself but
reportedly this patch solves some really weird problems where the
symptoms match (wrong files being opened unpredictably).
---
 fs/9p/vfs_inode.c      | 3 +++
 fs/9p/vfs_inode_dotl.c | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 30ca770c5e0b..f8ab4a66acaf 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -483,6 +483,9 @@ static int v9fs_test_inode(struct inode *inode, void *data)
 
 	if (v9inode->qid.type != st->qid.type)
 		return 0;
+
+	if (v9inode->qid.path != st->qid.path)
+		return 0;
 	return 1;
 }
 
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index afaa4b6de801..c3dd0d42bb3a 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -87,6 +87,9 @@ static int v9fs_test_inode_dotl(struct inode *inode, void *data)
 
 	if (v9inode->qid.type != st->qid.type)
 		return 0;
+
+	if (v9inode->qid.path != st->qid.path)
+		return 0;
 	return 1;
 }
 
-- 
2.11.1