linux-kernel - Re: [PATCH] fuse: verify all ioctl retry iov elements

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Date:	Mon, 06 Aug 2012 18:21:42 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Zach Brown <zab@...hat.com>
Cc:	fuse-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fuse: verify all ioctl retry iov elements

Zach Brown <zab@...hat.com> writes:

> Commit 7572777eef78ebdee1ecb7c258c0ef94d35bad16 attempted to verify that
> the total iovec from the client doesn't overflow iov_length() but it
> only checked the first element.  The iovec could still overflow by
> starting with a small element.  The obvious fix is to check all the
> elements.
>
> The overflow case doesn't look dangerous to the kernel as the copy is
> limited by the length after the overflow.  This fix restores the
> intention of returning an error instead of successfully copying less
> than the iovec represented.
>
> I found this by code inspection.  I built it but don't have a test case.
> I'm cc:ing stable because the initial commit did as well.

Thanks!  Applied.

Miklos


>
> Signed-off-by: Zach Brown <zab@...hat.com>
> CC: <stable@...nel.org>         [2.6.37+]
> ---
>  fs/fuse/file.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index b321a68..514f12a 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1700,7 +1700,7 @@ static int fuse_verify_ioctl_iov(struct iovec *iov, size_t count)
>  	size_t n;
>  	u32 max = FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT;
>  
> -	for (n = 0; n < count; n++) {
> +	for (n = 0; n < count; n++, iov++) {
>  		if (iov->iov_len > (size_t) max)
>  			return -ENOMEM;
>  		max -= iov->iov_len;
--
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