NFSD: Don't hold unrefcounted creds over call to nfsd_setuser()

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To: <git-commits-head@...>
Date: Saturday, July 4, 2009 - 1:59 pm

Gitweb:     http://git.kernel.org/linus/033a666ccb842ab4134fcd0c861d5ba9f5d6bf3a
Commit:     033a666ccb842ab4134fcd0c861d5ba9f5d6bf3a
Parent:     28d0325ce6e0a52f53d8af687e6427fee59004d3
Author:     David Howells <dhowells@redhat.com>
AuthorDate: Thu Jul 2 14:35:32 2009 +0100
Committer:  J. Bruce Fields <bfields@citi.umich.edu>
CommitDate: Fri Jul 3 10:21:10 2009 -0400

    NFSD: Don't hold unrefcounted creds over call to nfsd_setuser()
    
    nfsd_open() gets an unrefcounted pointer to the current process's effective
    credentials at the top of the function, then calls nfsd_setuser() via
    fh_verify() - which may replace and destroy the current process's effective
    credentials - and then passes the unrefcounted pointer to dentry_open() - but
    the credentials may have been destroyed by this point.
    
    Instead, the value from current_cred() should be passed directly to
    dentry_open() as one of its arguments, rather than being cached in a variable.
    
    Possibly fh_verify() should return the creds to use.
    
    This is a regression introduced by
    745ca2475a6ac596e3d8d37c2759c0fbe2586227 "CRED: Pass credentials through
    dentry_open()".
    
    Signed-off-by: David Howells <dhowells@redhat.com>
    Tested-and-Verified-By: Steve Dickson <steved@redhat.com>
    Cc: stable@kernel.org
    Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
---
 fs/nfsd/vfs.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 4145083..23341c1 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -678,7 +678,6 @@ __be32
 nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 			int access, struct file **filp)
 {
-	const struct cred *cred = current_cred();
 	struct dentry	*dentry;
 	struct inode	*inode;
 	int		flags = O_RDONLY|O_LARGEFILE;
@@ -733,7 +732,7 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 		vfs_dq_init(inode);
 	}
 	*filp = dentry_open(dget(dentry), mntget(fhp->fh_export->ex_path.mnt),
-			    flags, cred);
+			    flags, current_cred());
 	if (IS_ERR(*filp))
 		host_err = PTR_ERR(*filp);
 	else
--
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NFSD: Don't hold unrefcounted creds over call to nfsd_setuse..., Linux Kernel Mailing List..., (Sat Jul 4, 1:59 pm)