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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,
        Dominique Martinet <dominique.martinet@cea.fr>,
        syzbot+d4252148d198410b864f@syzkaller.appspotmail.com
Subject: [PATCH 4.19 030/110] v9fs_dir_readdir: fix double-free on p9stat_read error
Date:   Thu, 29 Nov 2018 15:12:01 +0100
Message-Id: <20181129135922.483812365@linuxfoundation.org>
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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dominique Martinet <dominique.martinet@cea.fr>

commit 81c99089bce693b94b775b6eb888115d2d540086 upstream.

p9stat_read will call p9stat_free on error, we should only free the
struct content on success.

There also is no need to "p9stat_init" st as the read function will
zero the whole struct for us anyway, so clean up the code a bit while
we are here.

Link: http://lkml.kernel.org/r/1535410108-20650-1-git-send-email-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Reported-by: syzbot+d4252148d198410b864f@syzkaller.appspotmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/9p/vfs_dir.c |   11 -----------
 1 file changed, 11 deletions(-)

--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -76,15 +76,6 @@ static inline int dt_type(struct p9_wsta
 	return rettype;
 }
 
-static void p9stat_init(struct p9_wstat *stbuf)
-{
-	stbuf->name  = NULL;
-	stbuf->uid   = NULL;
-	stbuf->gid   = NULL;
-	stbuf->muid  = NULL;
-	stbuf->extension = NULL;
-}
-
 /**
  * v9fs_alloc_rdir_buf - Allocate buffer used for read and readdir
  * @filp: opened file structure
@@ -145,12 +136,10 @@ static int v9fs_dir_readdir(struct file
 			rdir->tail = n;
 		}
 		while (rdir->head < rdir->tail) {
-			p9stat_init(&st);
 			err = p9stat_read(fid->clnt, rdir->buf + rdir->head,
 					  rdir->tail - rdir->head, &st);
 			if (err) {
 				p9_debug(P9_DEBUG_VFS, "returned %d\n", err);
-				p9stat_free(&st);
 				return -EIO;
 			}
 			reclen = st.size+2;