[PATCH -fixes] riscv: Fix wrong usage of lm_alias() when splitting a huge linear mapping

[Conor Dooley]

On Mon, Dec 11, 2023 at 03:19:29PM +0100, Alexandre Ghiti wrote:
> lm_alias() can only be used on kernel mappings since it explicitly uses
> __pa_symbol(), so simply fix this by checking where the address belongs
> to before.
> 
> Fixes: 311cd2f6e253 ("riscv: Fix set_memory_XX() and set_direct_map_XX() by splitting huge linear mappings")
> Reported-by: syzbot+afb726d49f84c8d95ee1 at syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/linux-riscv/000000000000620dd0060c02c5e1@google.com/
> Signed-off-by: Alexandre Ghiti <alexghiti at rivosinc.com>

../arch/riscv/mm/pageattr.c:311:14: warning: variable 'ret' is used uninitialized whenever '&&' condition is false [-Wsometimes-uninitialized]

> ---
>  arch/riscv/mm/pageattr.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
> index fc5fc4f785c4..f5f8aa1d38d6 100644
> --- a/arch/riscv/mm/pageattr.c
> +++ b/arch/riscv/mm/pageattr.c
> @@ -304,9 +304,16 @@ static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
>  			if (ret)
>  				goto unlock;
>  		}
> -	} else if (is_kernel_mapping(start) || is_linear_mapping(start)) {
> -		lm_start = (unsigned long)lm_alias(start);
> -		lm_end = (unsigned long)lm_alias(end);
> +	} else {
> +		if (is_kernel_mapping(start)) {
> +			lm_start = (unsigned long)lm_alias(start);
> +			lm_end = (unsigned long)lm_alias(end);
> +		} else if (is_linear_mapping(start)) {
> +			lm_start = start;
> +			lm_end = end;
> +		} else {
> +			goto unlock;
> +		}
>  
>  		ret = split_linear_mapping(lm_start, lm_end);
>  		if (ret)
> -- 
> 2.39.2
> 
> 
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