NFS: nfs_igrab_and_active must first reference the superblock

Trond Myklebust · Trond Myklebust · commit 896567ee7f17 · 2021-01-10T16:29:28.000-05:00
Before referencing the inode, we must ensure that the superblock can be referenced. Otherwise, we can end up with iput() calling superblock operations that are no longer valid or accessible. Fixes: ea7c38f ("NFSv4: Ensure we reference the inode for return-on-close in delegreturn") Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
@@ -599,12 +599,14 @@ extern void nfs4_test_session_trunk(struct rpc_clnt *clnt,
 
 static inline struct inode *nfs_igrab_and_active(struct inode *inode)
 {
-	inode = igrab(inode);
-	if (inode != NULL && !nfs_sb_active(inode->i_sb)) {
-		iput(inode);
-		inode = NULL;
+	struct super_block *sb = inode->i_sb;
+
+	if (sb && nfs_sb_active(sb)) {
+		if (igrab(inode))
+			return inode;
+		nfs_sb_deactive(sb);
 	}
-	return inode;
+	return NULL;
 }
 
 static inline void nfs_iput_and_deactive(struct inode *inode)

Original file line number	Diff line number	Diff line change
`@@ -599,12 +599,14 @@ extern void nfs4_test_session_trunk(struct rpc_clnt *clnt,`
`599`	`599`
`600`	`600`	`static inline struct inode nfs_igrab_and_active(struct inode inode)`
`601`	`601`	`{`
`602`		`- inode = igrab(inode);`
`603`		`- if (inode != NULL && !nfs_sb_active(inode->i_sb)) {`
`604`		`- iput(inode);`
`605`		`- inode = NULL;`
	`602`	`+ struct super_block *sb = inode->i_sb;`
	`603`	`+`
	`604`	`+ if (sb && nfs_sb_active(sb)) {`
	`605`	`+ if (igrab(inode))`
	`606`	`+ return inode;`
	`607`	`+ nfs_sb_deactive(sb);`
`606`	`608`	`}`
`607`		`- return inode;`
	`609`	`+ return NULL;`
`608`	`610`	`}`
`609`	`611`
`610`	`612`	`static inline void nfs_iput_and_deactive(struct inode *inode)`