RE: [PATCH] iov_iter: fix the uaccess area in copy_compat_iovec_from_user

[David Laight <David.Laight@ACULAB.COM>]

From: Christoph Hellwig
> Sent: 11 January 2021 17:19
> 
> sizeof needs to be called on the compat pointer, not the native one.
> 
> Fixes: 89cd35c58bc2 ("iov_iter: transparently handle compat iovecs in import_iovec")
> Reported-by: David Laight <David.Laight@ACULAB.COM>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  lib/iov_iter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 1635111c5bd2af..586215aa0f15ce 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1658,7 +1658,7 @@ static int copy_compat_iovec_from_user(struct iovec *iov,
>  		(const struct compat_iovec __user *)uvec;
>  	int ret = -EFAULT, i;
> 
> -	if (!user_access_begin(uvec, nr_segs * sizeof(*uvec)))
> +	if (!user_access_begin(uvec, nr_segs * sizeof(*uiov)))

The first 'uvec' probably ought to be changed as well.
Even though both variables have the same value.

	David

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