Commit 2c1cf00e authored Jan 31, 2019 by Greg Kroah-Hartman

relay: check return of create_buf_file() properly



If create_buf_file() returns an error, don't try to reference it later
as a valid dentry pointer.

This problem was exposed when debugfs started to return errors instead
of just NULL for some calls when they do not succeed properly.

Also, the check for WARN_ON(dentry) was just wrong :)

Reported-by: Kees Cook <keescook@chromium.org>
Reported-and-tested-by:  <syzbot+16c3a70e1e9b29346c43@syzkaller.appspotmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Fixes: ff9fb72b ("debugfs: return error values, not NULL")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 37ea7b63

kernel/relay.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -428,6 +428,8 @@ static struct dentry relay_create_buf_file(struct rchan chan,
		dentry = chan->cb->create_buf_file(tmpname, chan->parent,
		S_IRUSR, buf,
		&chan->is_global);
		if (IS_ERR(dentry))
		dentry = NULL;

		kfree(tmpname);

		@@ -461,7 +463,7 @@ static struct rchan_buf relay_open_buf(struct rchan chan, unsigned int cpu)
		dentry = chan->cb->create_buf_file(NULL, NULL,
		S_IRUSR, buf,
		&chan->is_global);
		if (WARN_ON(dentry))
		if (IS_ERR_OR_NULL(dentry))
		goto free_buf;
		}

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