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net/9p: validate fds in p9_fd_open

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[ Upstream commit a39c46067c ]

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>
This commit is contained in:
Christoph Hellwig 2020-07-10 10:57:22 +02:00 committed by Greg Kroah-Hartman
parent 6ed5651140
commit af224c2eed
1 changed files with 16 additions and 8 deletions
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24
net/9p/trans_fd.c
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@ -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)