linux-kernel - [PATCH] nfsd: fix NULL dereference in nfsd

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Date:	Fri, 13 Aug 2010 15:53:49 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Neil Brown <neilb@...e.de>, Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@....de>, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] nfsd: fix NULL dereference in nfsd_statfs()

The commit ebabe9a9001af0af56c0c2780ca1576246e7a74b
    pass a struct path to vfs_statfs
introduced the struct path initialization, and this seems to trigger
an Oops on my machine.

fh_dentry field may be NULL and set later in fh_verify(), thus the
initialization of path must be after fh_verify().

Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 fs/nfsd/vfs.c |   14 ++++++++------
 1 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 96360a8..661a6cf 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -2033,15 +2033,17 @@ out:
 __be32
 nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
 {
-	struct path path = {
-		.mnt	= fhp->fh_export->ex_path.mnt,
-		.dentry	= fhp->fh_dentry,
-	};
 	__be32 err;
 
 	err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
-	if (!err && vfs_statfs(&path, stat))
-		err = nfserr_io;
+	if (!err) {
+		struct path path = {
+			.mnt	= fhp->fh_export->ex_path.mnt,
+			.dentry	= fhp->fh_dentry,
+		};
+		if (vfs_statfs(&path, stat))
+			err = nfserr_io;
+	}
 	return err;
 }
 
-- 
1.7.2.1

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