From: Christoph Hellwig <hch@xxxxxx> [ 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@xxxxxx Reported-by: syzbot+e6f77e16ff68b2434a2c@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Christoph Hellwig <hch@xxxxxx> [Dominique: amend goto as per Doug Nazar's review] Signed-off-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 3f67803123be2..12ecacf0c55fb 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -816,20 +816,28 @@ 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) -- 2.25.1
