From edd90971717e4ec35506ba134c9bcfacf0dcd31c Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 10 Jul 2020 10:57:22 +0200 Subject: [PATCH] net/9p: validate fds in p9_fd_open [ Upstream commit a39c46067c845a8a2d7144836e9468b7f072343e ] p9_fd_open just fgets file descriptors passed in from userspace, but doesn't verify that they are valid for read or writing. This gets cought down in the VFS when actually attempting a read or write, but a new warning added in linux-next upsets syzcaller. Fix this by just verifying the fds early on. Link: http://lkml.kernel.org/r/20200710085722.435850-1-hch@lst.de Reported-by: syzbot+e6f77e16ff68b2434a2c@syzkaller.appspotmail.com Signed-off-by: Christoph Hellwig [Dominique: amend goto as per Doug Nazar's review] Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin --- net/9p/trans_fd.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index b0f4756..bad27b0 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -815,20 +815,28 @@ static int p9_fd_open(struct p9_client *client, int rfd, int wfd) return -ENOMEM; ts->rd = fget(rfd); + if (!ts->rd) + goto out_free_ts; + if (!(ts->rd->f_mode & FMODE_READ)) + goto out_put_rd; ts->wr = fget(wfd); - if (!ts->rd || !ts->wr) { - if (ts->rd) - fput(ts->rd); - if (ts->wr) - fput(ts->wr); - kfree(ts); - return -EIO; - } + if (!ts->wr) + goto out_put_rd; + if (!(ts->wr->f_mode & FMODE_WRITE)) + goto out_put_wr; client->trans = ts; client->status = Connected; return 0; + +out_put_wr: + fput(ts->wr); +out_put_rd: + fput(ts->rd); +out_free_ts: + kfree(ts); + return -EIO; } static int p9_socket_open(struct p9_client *client, struct socket *csocket) -- 2.7.4