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Subject: [PATCH 4/5] smb3: missing inode locks in punch hole
From:   David Howells <dhowells@redhat.com>
To:     sfrench@samba.org, linux-cifs@vger.kernel.org
Cc:     lsahlber@redhat.com, jlayton@kernel.org, dchinner@redhat.com,
        willy@infradead.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, samba-technical@lists.samba.org
Date:   Tue, 23 Aug 2022 14:07:48 +0100
Message-ID: <166126006871.548536.9826412629988468617.stgit@warthog.procyon.org.uk>
In-Reply-To: <166126004083.548536.11195647088995116235.stgit@warthog.procyon.org.uk>
References: <166126004083.548536.11195647088995116235.stgit@warthog.procyon.org.uk>
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Precedence: bulk

smb3 fallocate punch hole was not grabbing the inode or filemap_invalidate
locks so could have race with pagemap reinstantiating the page.

Cc: stable@vger.kernel.org
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---

 fs/cifs/smb2ops.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 75fcf6a0df56..5b5ddc1b4638 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3375,7 +3375,7 @@ static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
 			    loff_t offset, loff_t len)
 {
-	struct inode *inode;
+	struct inode *inode = file_inode(file);
 	struct cifsFileInfo *cfile = file->private_data;
 	struct file_zero_data_information fsctl_buf;
 	long rc;
@@ -3384,14 +3384,12 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
 
 	xid = get_xid();
 
-	inode = d_inode(cfile->dentry);
-
+	inode_lock(inode);
 	/* Need to make file sparse, if not already, before freeing range. */
 	/* Consider adding equivalent for compressed since it could also work */
 	if (!smb2_set_sparse(xid, tcon, cfile, inode, set_sparse)) {
 		rc = -EOPNOTSUPP;
-		free_xid(xid);
-		return rc;
+		goto out;
 	}
 
 	filemap_invalidate_lock(inode->i_mapping);
@@ -3411,8 +3409,10 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
 			(char *)&fsctl_buf,
 			sizeof(struct file_zero_data_information),
 			CIFSMaxBufSize, NULL, NULL);
-	free_xid(xid);
 	filemap_invalidate_unlock(inode->i_mapping);
+out:
+	inode_unlock(inode);
+	free_xid(xid);
 	return rc;
 }