[bug report] SUNRPC: simplify auth_unix.

[bug report] SUNRPC: simplify auth_unix.

[Dan Carpenter]

Hello NeilBrown,

This is a semi-automatic email about new static checker warnings.

The patch 394f319df78e: "SUNRPC: simplify auth_unix." from Dec 3, 
2018, leads to the following Smatch complaint:

    net/sunrpc/auth_unix.c:90 unx_match()
    warn: variable dereferenced before check 'acred->cred' (see line 87)

net/sunrpc/auth_unix.c
    86	
    87		if (!uid_eq(cred->cr_cred->fsuid, acred->cred->fsuid) || !gid_eq(cred->cr_cred->fsgid, acred->cred->fsgid))
                                                  ^^^^^^^^^^^
New dereference

    88			return 0;
    89	
    90		if (acred->cred && acred->cred->group_info != NULL)
                    ^^^^^^^^^^^
But the old code checked for NULL

    91			groups = acred->cred->group_info->ngroups;
    92		if (groups > UNX_NGROUPS)

regards,
dan carpenter

[PATCH] SUNRPC: remove pointless test in unx_match()

[NeilBrown]

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As reported by Dan Carpenter, this test for acred->cred being set is
inconsistent with the dereference of the pointer a few lines earlier.

An 'auth_cred' *always* has ->cred set - every place that creates one
initializes this field, often as the first thing done.

So remove this test.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NeilBrown <neilb@suse.com>
---
 net/sunrpc/auth_unix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index 387f6b3ffbea..770e338a9b11 100644
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -87,7 +87,7 @@ unx_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
 	if (!uid_eq(cred->cr_cred->fsuid, acred->cred->fsuid) || !gid_eq(cred->cr_cred->fsgid, acred->cred->fsgid))
 		return 0;
 
-	if (acred->cred && acred->cred->group_info != NULL)
+	if (acred->cred->group_info != NULL)
 		groups = acred->cred->group_info->ngroups;
 	if (groups > UNX_NGROUPS)
 		groups = UNX_NGROUPS;
-- 
2.14.0.rc0.dirty


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Re: [PATCH] SUNRPC: remove pointless test in unx_match()

[Trond Myklebust]

On Mon, 2019-01-07 at 17:53 +1100, NeilBrown wrote:
> As reported by Dan Carpenter, this test for acred->cred being set is
> inconsistent with the dereference of the pointer a few lines earlier.
> 
> An 'auth_cred' *always* has ->cred set - every place that creates one
> initializes this field, often as the first thing done.
> 
> So remove this test.
> 
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: NeilBrown <neilb@suse.com>
> 

Thanks Neil! Applied to the linux-next branch for inclusion in the 5.1
merge window.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com