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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Anna Schumaker <Anna.Schumaker@Netapp.com>,
        Trond Myklebust <trond.myklebust@hammerspace.com>
Subject: [PATCH 5.12 021/296] NFSv4: Fix a NULL pointer dereference in pnfs_mark_matching_lsegs_return()
Date:   Mon, 31 May 2021 15:11:16 +0200
Message-Id: <20210531130704.481153525@linuxfoundation.org>
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From: Anna Schumaker <Anna.Schumaker@Netapp.com>

commit a421d218603ffa822a0b8045055c03eae394a7eb upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/nfs/pnfs.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1317,6 +1317,11 @@ _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);
 	const struct cred *cred;
 	nfs4_stateid stateid;
@@ -1344,16 +1349,10 @@ _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) ||