linux-kernel - Re: fs: out of bounds on stack in iov_iter

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Message-ID: <CA+55aFyg1h9feLQU0k2LviDtuiGx8WLCEvW0U+AxcvD-RZ+z7Q@mail.gmail.com>
Date:	Tue, 10 Nov 2015 18:31:49 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Sasha Levin <sasha.levin@...cle.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Chuck Ebbert <cebbert.lkml@...il.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dan Williams <dan.j.williams@...el.com>
Subject: Re: fs: out of bounds on stack in iov_iter_advance

On Tue, Nov 10, 2015 at 6:25 PM, Jens Axboe <axboe@...nel.dk> wrote:
> On Tue, Nov 10 2015, Linus Torvalds wrote:
>> Al, ping?
>>
>> On Thu, Nov 5, 2015 at 7:38 PM, Linus Torvalds
>> <torvalds@...ux-foundation.org> wrote:
>> > On Thu, Nov 5, 2015 at 6:19 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>> >>
>> >> How are we going to handle that one?  I can put it into mainline pull
>> >> request via vfs.git, with Cc: stable, but if e.g. Jens prefers to take it
>> >> via the block tree, I'll be glad to leave it for him to deal with.
>> >
>> > Put it in the vfs tree (I'm hoping for a pull request soon..)
>> >
>> > I pulled the block trees from Jens yesterday, so there is presumably
>> > nothing pending there right now.
>>
>> Apparently my "hoping for a pull request soon" was ridiculously optimistic.
>>
>> Al, looking at the most recent linux-next, most of the vfs commits
>> there seem to be committed in the last day or two. I'm getting the
>> feeling that that is all 4.5 material by now.
>>
>> Should I just take the iov patch as-is, since apparently no vfs pull
>> request is happening this merge cycle? And no, I'm not taking
>> "developed during the second week of the merge window, and sent in the
>> last few days of it". I'm done with that.
>
> I've got 8 other patches pending for a post core merge, just waiting for
> the last core pull request to go in. I haven't seen this iov iter fix,
> though.

It was in this thread, looked like this (without the whitespace damage):

    dax_io(): don't let non-error value escape via retval instead of EFAULT

    Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
    ---
    diff --git a/fs/dax.c b/fs/dax.c
    index a86d3cc..7b653e9 100644
    --- a/fs/dax.c
    +++ b/fs/dax.c
    @@ -169,8 +169,10 @@ static ssize_t dax_io(struct inode *inode,
struct iov_iter *iter,
                    else
                            len = iov_iter_zero(max - pos, iter);

    -               if (!len)
    +               if (!len) {
    +                       retval = -EFAULT;
                            break;
    +               }

                    pos += len;
                    addr += len;


although I don't think I saw a confirmation that that was what Sasha
actually hit (but Sasha had narrowed it down to DAX, so it looks
possible/likely)

                    Linus
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