[PATCH] NFSv4: Fixup smatch warning for ambiguous return

[PATCH] NFSv4: Fixup smatch warning for ambiguous return

[Benjamin Coddington]

Dan Carpenter reports smatch warning for nfs4_try_migration() when a memory
allocation failure results in a zero return value.  In this case, a
transient allocation failure error will likely be retried the next time the
server responds with NFS4ERR_MOVED.

We can fixup the smatch warning with a small refactor: attempt all three
allocations before testing and returning on a failure.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Fixes: c3ed222745d9 ("NFSv4: Fix free of uninitialized nfs4_label on referral lookup.")
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
---
Chuck, does this look sane?  I don't have a simple way to test this at the
moment.  Also, I think the only result of returning -ENOMEM here instead
would be that we skip continuing to try to migrate for other filesystems on
this client, and we'd get a log message and trace output of the failure.

 fs/nfs/nfs4state.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 662e86ea3a2d..5b452411e8fd 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -2116,6 +2116,7 @@ static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred
 {
 	struct nfs_client *clp = server->nfs_client;
 	struct nfs4_fs_locations *locations = NULL;
+	struct nfs_fattr *fattr;
 	struct inode *inode;
 	struct page *page;
 	int status, result;
@@ -2125,19 +2126,16 @@ static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred
 			(unsigned long long)server->fsid.minor,
 			clp->cl_hostname);
 
-	result = 0;
 	page = alloc_page(GFP_KERNEL);
 	locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
-	if (page == NULL || locations == NULL) {
-		dprintk("<-- %s: no memory\n", __func__);
-		goto out;
-	}
-	locations->fattr = nfs_alloc_fattr();
-	if (locations->fattr == NULL) {
+	fattr = nfs_alloc_fattr();
+	if (page == NULL || locations == NULL || fattr == NULL) {
 		dprintk("<-- %s: no memory\n", __func__);
+		result = 0;
 		goto out;
 	}
 
+	locations->fattr = fattr;
 	inode = d_inode(server->super->s_root);
 	result = nfs4_proc_get_locations(server, NFS_FH(inode), locations,
 					 page, cred);
-- 
2.44.0

Re: [PATCH] NFSv4: Fixup smatch warning for ambiguous return

[Dan Carpenter]

On Wed, Apr 17, 2024 at 02:49:29PM -0400, Benjamin Coddington wrote:
> Dan Carpenter reports smatch warning for nfs4_try_migration() when a memory
> allocation failure results in a zero return value.  In this case, a
> transient allocation failure error will likely be retried the next time the
> server responds with NFS4ERR_MOVED.
> 
> We can fixup the smatch warning with a small refactor: attempt all three
> allocations before testing and returning on a failure.
> 
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Fixes: c3ed222745d9 ("NFSv4: Fix free of uninitialized nfs4_label on referral lookup.")
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> ---

This preserves the existing behavior and makes the code more readable.

Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>

regards,
dan carpenter

Re: [PATCH] NFSv4: Fixup smatch warning for ambiguous return

[Chuck Lever]

On Wed, Apr 17, 2024 at 02:49:29PM -0400, Benjamin Coddington wrote:
> Dan Carpenter reports smatch warning for nfs4_try_migration() when a memory
> allocation failure results in a zero return value.  In this case, a
> transient allocation failure error will likely be retried the next time the
> server responds with NFS4ERR_MOVED.
> 
> We can fixup the smatch warning with a small refactor: attempt all three
> allocations before testing and returning on a failure.
> 
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Fixes: c3ed222745d9 ("NFSv4: Fix free of uninitialized nfs4_label on referral lookup.")
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> ---
> Chuck, does this look sane?  I don't have a simple way to test this at the
> moment.  Also, I think the only result of returning -ENOMEM here instead
> would be that we skip continuing to try to migrate for other filesystems on
> this client, and we'd get a log message and trace output of the failure.

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>


>  fs/nfs/nfs4state.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index 662e86ea3a2d..5b452411e8fd 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -2116,6 +2116,7 @@ static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred
>  {
>  	struct nfs_client *clp = server->nfs_client;
>  	struct nfs4_fs_locations *locations = NULL;
> +	struct nfs_fattr *fattr;
>  	struct inode *inode;
>  	struct page *page;
>  	int status, result;
> @@ -2125,19 +2126,16 @@ static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred
>  			(unsigned long long)server->fsid.minor,
>  			clp->cl_hostname);
>  
> -	result = 0;
>  	page = alloc_page(GFP_KERNEL);
>  	locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
> -	if (page == NULL || locations == NULL) {
> -		dprintk("<-- %s: no memory\n", __func__);
> -		goto out;
> -	}
> -	locations->fattr = nfs_alloc_fattr();
> -	if (locations->fattr == NULL) {
> +	fattr = nfs_alloc_fattr();
> +	if (page == NULL || locations == NULL || fattr == NULL) {
>  		dprintk("<-- %s: no memory\n", __func__);
> +		result = 0;
>  		goto out;
>  	}
>  
> +	locations->fattr = fattr;
>  	inode = d_inode(server->super->s_root);
>  	result = nfs4_proc_get_locations(server, NFS_FH(inode), locations,
>  					 page, cred);
> -- 
> 2.44.0
> 

-- 
Chuck Lever