From: Christoph Hellwig hch@lst.de
[ 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 hch@lst.de [Dominique: amend goto as per Doug Nazar's review] Signed-off-by: Dominique Martinet asmadeus@codewreck.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 d28c2cc9618f..b6dcb40fa8a7 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -831,20 +831,28 @@ 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)