linux-kernel - Re: [PATCH] riscv: fix __user annotation in traps

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Date:   Thu, 23 Nov 2023 22:05:19 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu
Subject: Re: [PATCH] riscv: fix __user annotation in traps_misaligned.c

On Thu, Nov 23, 2023 at 02:16:17PM +0000, Ben Dooks wrote:
> @@ -319,7 +319,7 @@ static inline int get_insn(struct pt_regs *regs, ulong mepc, ulong *r_insn)
>  static inline int load_u8(struct pt_regs *regs, const u8 *addr, u8 *r_val)
>  {
>  	if (user_mode(regs)) {
> -		return __get_user(*r_val, addr);
> +		return __get_user(*r_val, (u8 __user *)addr);
>  	} else {
>  		*r_val = *addr;
>  		return 0;

This is the wrong way to approach it.  Pass the untype unsigned long
from the caller instead and do a single round of casts from that
depending on the address_space.

And please also remove this horrible else after return entipattern
while you're at it.