linux-kernel - Re: [PATCH] Revert "riscv: misaligned: fix sleeping function called during misaligned access handling"

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Message-ID: <e435366d-f561-41d6-ad25-9f8c96e61f24@rivosinc.com>
Date: Fri, 20 Jun 2025 13:52:12 +0200
From: Clément Léger <cleger@...osinc.com>
To: Nam Cao <namcao@...utronix.de>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, Nylon Chen <nylon.chen@...ive.com>,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org
Subject: Re: [PATCH] Revert "riscv: misaligned: fix sleeping function called
 during misaligned access handling"



On 20/06/2025 13:09, Nam Cao wrote:
> This reverts commit 61a74ad25462 ("riscv: misaligned: fix sleeping function
> called during misaligned access handling"). The commit addresses a sleeping
> in atomic context problem, but it is not the correct fix as explained by
> Clément:
> 
> "Using nofault would lead to failure to read from user memory that is paged
> out for instance. This is not really acceptable, we should handle user
> misaligned access even at an address that would generate a page fault."
> 
> This bug has been properly fixed by commit 453805f0a28f ("riscv:
> misaligned: enable IRQs while handling misaligned accesses").
> 
> Revert this improper fix.
> 
> Link: https://lore.kernel.org/linux-riscv/b779beed-e44e-4a5e-9551-4647682b0d21@rivosinc.com/
> Signed-off-by: Nam Cao <namcao@...utronix.de>
> Cc: stable@...r.kernel.org
> ---
>  arch/riscv/kernel/traps_misaligned.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> index dd8e4af6583f4..93043924fe6c6 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -454,7 +454,7 @@ static int handle_scalar_misaligned_load(struct pt_regs *regs)
>  
>  	val.data_u64 = 0;
>  	if (user_mode(regs)) {
> -		if (copy_from_user_nofault(&val, (u8 __user *)addr, len))
> +		if (copy_from_user(&val, (u8 __user *)addr, len))
>  			return -1;
>  	} else {
>  		memcpy(&val, (u8 *)addr, len);
> @@ -555,7 +555,7 @@ static int handle_scalar_misaligned_store(struct pt_regs *regs)
>  		return -EOPNOTSUPP;
>  
>  	if (user_mode(regs)) {
> -		if (copy_to_user_nofault((u8 __user *)addr, &val, len))
> +		if (copy_to_user((u8 __user *)addr, &val, len))
>  			return -1;
>  	} else {
>  		memcpy((u8 *)addr, &val, len);

Hi Nam,

Reviewed-by: Clément Léger <cleger@...osinc.com>

Thanks for noticing that.