linux-kernel - [PATCH] Infiniband: Fix potential NULL d

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Date:	Tue, 27 Jan 2015 15:01:18 +0000
From:	David Howells <dhowells@...hat.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	infinipath@...el.com, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org, dhowells@...hat.com,
	"Bryan O'Sullivan" <bos@...hscale.com>, viro@...iv.linux.org.uk,
	Roland Dreier <rolandd@...co.com>
Subject: [PATCH] Infiniband: Fix potential NULL d_inode dereference

Code that does this:

	if (!(d_unhashed(tmp) && tmp->d_inode)) {
		...
		simple_unlink(parent->d_inode, tmp);
	}

is broken because:

	!(d_unhashed(tmp) && tmp->d_inode)

is equivalent to:

	!d_unhashed(tmp) || !tmp->d_inode

so it is possible to get into simple_unlink() with tmp->d_inode == NULL.

simple_unlink(), however, assumes tmp->d_inode cannot be NULL.

I think that what was meant is this:

	!d_unhashed(tmp) && tmp->d_inode

and that the logical-not operator or the final close-bracket was misplaced.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Bryan O'Sullivan <bos@...hscale.com>
cc: Roland Dreier <rolandd@...co.com>
---

 drivers/infiniband/hw/ipath/ipath_fs.c |    2 +-
 drivers/infiniband/hw/qib/qib_fs.c     |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/ipath/ipath_fs.c b/drivers/infiniband/hw/ipath/ipath_fs.c
index 4977082e081f..33c45dfcbd88 100644
--- a/drivers/infiniband/hw/ipath/ipath_fs.c
+++ b/drivers/infiniband/hw/ipath/ipath_fs.c
@@ -277,7 +277,7 @@ static int remove_file(struct dentry *parent, char *name)
 	}
 
 	spin_lock(&tmp->d_lock);
-	if (!(d_unhashed(tmp) && tmp->d_inode)) {
+	if (!d_unhashed(tmp) && tmp->d_inode) {
 		dget_dlock(tmp);
 		__d_drop(tmp);
 		spin_unlock(&tmp->d_lock);
diff --git a/drivers/infiniband/hw/qib/qib_fs.c b/drivers/infiniband/hw/qib/qib_fs.c
index 81854586c081..d2427640d7e9 100644
--- a/drivers/infiniband/hw/qib/qib_fs.c
+++ b/drivers/infiniband/hw/qib/qib_fs.c
@@ -455,7 +455,7 @@ static int remove_file(struct dentry *parent, char *name)
 	}
 
 	spin_lock(&tmp->d_lock);
-	if (!(d_unhashed(tmp) && tmp->d_inode)) {
+	if (!d_unhashed(tmp) && tmp->d_inode) {
 		__d_drop(tmp);
 		spin_unlock(&tmp->d_lock);
 		simple_unlink(parent->d_inode, tmp);

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