linux-kernel - [PATCH 1/2] v9fs_dir_readdir: fix double-free on p9stat

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Message-Id: <1535410108-20650-1-git-send-email-asmadeus@codewreck.org>
Date:   Tue, 28 Aug 2018 00:48:27 +0200
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     v9fs-developer@...ts.sourceforge.net
Cc:     Dominique Martinet <dominique.martinet@....fr>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com,
        Eric Van Hensbergen <ericvh@...il.com>,
        Latchesar Ionkov <lucho@...kov.net>
Subject: [PATCH 1/2] v9fs_dir_readdir: fix double-free on p9stat_read error

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

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.

Signed-off-by: Dominique Martinet <dominique.martinet@....fr>
Reported-by: syzbot+d4252148d198410b864f@...kaller.appspotmail.com
Cc: Eric Van Hensbergen <ericvh@...il.com>
Cc: Latchesar Ionkov <lucho@...kov.net>
---
 fs/9p/vfs_dir.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c
index b0405d6aac85..48db9a9f13f9 100644
--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -76,15 +76,6 @@ static inline int dt_type(struct p9_wstat *mistat)
 	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 *file, struct dir_context *ctx)
 			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;
-- 
2.17.1