From: Anna Schumaker <Anna.Schumaker@Netapp.com>
Date: Wed, 19 May 2021 12:54:51 -0400
Subject: [PATCH] NFSv4: Fix a NULL pointer dereference in
 pnfs_mark_matching_lsegs_return()
Git-commit: a421d218603ffa822a0b8045055c03eae394a7eb
Patch-mainline: v5.13
References: git-fixes

Commit de144ff4234f changes _pnfs_return_layout() to call
pnfs_mark_matching_lsegs_return() passing NULL as the struct
pnfs_layout_range argument. Unfortunately,
pnfs_mark_matching_lsegs_return() doesn't check if we have a value here
before dereferencing it, causing an oops.

I'm able to hit this crash consistently when running connectathon basic
tests on NFS v4.1/v4.2 against Ontap.

Fixes: de144ff4234f ("NFSv4: Don't discard segments marked for return in _pnfs_return_layout()")
Cc: stable@vger.kernel.org
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/pnfs.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1177,6 +1177,11 @@ _pnfs_return_layout(struct inode *ino)
 {
 	struct pnfs_layout_hdr *lo = NULL;
 	struct nfs_inode *nfsi = NFS_I(ino);
+	struct pnfs_layout_range range = {
+		.iomode		= IOMODE_ANY,
+		.offset		= 0,
+		.length		= NFS4_MAX_UINT64,
+	};
 	LIST_HEAD(tmp_list);
 	nfs4_stateid stateid;
 	int status = 0;
@@ -1203,16 +1208,10 @@ _pnfs_return_layout(struct inode *ino)
 	}
 	valid_layout = pnfs_layout_is_valid(lo);
 	pnfs_clear_layoutcommit(ino, &tmp_list);
-	pnfs_mark_matching_lsegs_return(lo, &tmp_list, NULL, 0);
+	pnfs_mark_matching_lsegs_return(lo, &tmp_list, &range, 0);
 
-	if (NFS_SERVER(ino)->pnfs_curr_ld->return_range) {
-		struct pnfs_layout_range range = {
-			.iomode		= IOMODE_ANY,
-			.offset		= 0,
-			.length		= NFS4_MAX_UINT64,
-		};
+	if (NFS_SERVER(ino)->pnfs_curr_ld->return_range)
 		NFS_SERVER(ino)->pnfs_curr_ld->return_range(lo, &range);
-	}
 
 	/* Don't send a LAYOUTRETURN if list was initially empty */
 	if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags) ||