Re: [PATCH] x86/compat: Pull huge_encode_dev() outside of UACCESS

[Randy Dunlap <rdunlap@infradead.org>]

On 1/4/21 7:53 AM, Peter Zijlstra wrote:
> On Mon, Jan 04, 2021 at 09:31:27AM -0600, Josh Poimboeuf wrote:
>> Peter, care to submit a proper patch?
> 
> Here goes..
> 
> ---
> Subject: x86/compat: Pull huge_encode_dev() outside of UACCESS
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Mon, 4 Jan 2021 13:28:25 +0100
> 
> Fixes the following warning:
> 
>   arch/x86/kernel/sys_ia32.o: warning: objtool: cp_stat64()+0xd8: call to new_encode_dev() with UACCESS enabled
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

Thanks.

> ---
>  arch/x86/kernel/sys_ia32.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> --- a/arch/x86/kernel/sys_ia32.c
> +++ b/arch/x86/kernel/sys_ia32.c
> @@ -133,18 +133,23 @@ static int cp_stat64(struct stat64 __use
>  {
>  	typeof(ubuf->st_uid) uid = 0;
>  	typeof(ubuf->st_gid) gid = 0;
> +	u64 dev, rdev;
> +
>  	SET_UID(uid, from_kuid_munged(current_user_ns(), stat->uid));
>  	SET_GID(gid, from_kgid_munged(current_user_ns(), stat->gid));
> +	dev = huge_encode_dev(stat->dev);
> +	rdev = huge_encode_dev(stat->rdev);
> +
>  	if (!user_write_access_begin(ubuf, sizeof(struct stat64)))
>  		return -EFAULT;
> -	unsafe_put_user(huge_encode_dev(stat->dev), &ubuf->st_dev, Efault);
> +	unsafe_put_user(dev, &ubuf->st_dev, Efault);
>  	unsafe_put_user(stat->ino, &ubuf->__st_ino, Efault);
>  	unsafe_put_user(stat->ino, &ubuf->st_ino, Efault);
>  	unsafe_put_user(stat->mode, &ubuf->st_mode, Efault);
>  	unsafe_put_user(stat->nlink, &ubuf->st_nlink, Efault);
>  	unsafe_put_user(uid, &ubuf->st_uid, Efault);
>  	unsafe_put_user(gid, &ubuf->st_gid, Efault);
> -	unsafe_put_user(huge_encode_dev(stat->rdev), &ubuf->st_rdev, Efault);
> +	unsafe_put_user(rdev, &ubuf->st_rdev, Efault);
>  	unsafe_put_user(stat->size, &ubuf->st_size, Efault);
>  	unsafe_put_user(stat->atime.tv_sec, &ubuf->st_atime, Efault);
>  	unsafe_put_user(stat->atime.tv_nsec, &ubuf->st_atime_nsec, Efault);
> 


-- 
~Randy