[PATCH 3.16 073/328] fuse: Fix oops at process_init_reply()

Ben Hutchings
2018-12-09T22:06:03Z

From: Miklos Szeredi <mszeredi@redhat.com>

commit e8f3bd773d22f488724dffb886a1618da85c2966 upstream.

syzbot is hitting NULL pointer dereference at process_init_reply().
This is because deactivate_locked_super() is called before response for
initial request is processed.

Fix this by aborting and waiting for all requests (including FUSE_INIT)
before resetting fc->sb.

Original patch by Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>.

Reported-by: syzbot <syzbot+b62f08f4d5857755e3bc@syzkaller.appspotmail.com>
Fixes: e27c9d3877a0 ("fuse: fuse: add time_gran to INIT_OUT")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
[bwh: Backported to 3.16:
- Drop second argument to fuse_abort_conn()
- fuse_wait_aborted() is not needed]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -380,9 +380,6 @@ static void fuse_put_super(struct super_
{
struct fuse_conn *fc = get_fuse_conn_super(sb);

- fuse_send_destroy(fc);
-
- fuse_abort_conn(fc);
mutex_lock(&fuse_mutex);
list_del(&fc->entry);
fuse_ctl_remove_conn(fc);
@@ -1124,16 +1121,24 @@ static struct dentry *fuse_mount(struct
return mount_nodev(fs_type, flags, raw_data, fuse_fill_super);
}

-static void fuse_kill_sb_anon(struct super_block *sb)
+static void fuse_sb_destroy(struct super_block *sb)
{
struct fuse_conn *fc = get_fuse_conn_super(sb);

if (fc) {
+ fuse_send_destroy(fc);
+
+ fuse_abort_conn(fc);
+
down_write(&fc->killsb);
fc->sb = NULL;
up_write(&fc->killsb);
}
+}

+static void fuse_kill_sb_anon(struct super_block *sb)
+{
+ fuse_sb_destroy(sb);
kill_anon_super(sb);
}

@@ -1156,14 +1161,7 @@ static struct dentry *fuse_mount_blk(str

static void fuse_kill_sb_blk(struct super_block *sb)
{
- struct fuse_conn *fc = get_fuse_conn_super(sb);
-
- if (fc) {
- down_write(&fc->killsb);
- fc->sb = NULL;
- up_write(&fc->killsb);
- }
-
+ fuse_sb_destroy(sb);
kill_block_super(sb);
}