Re: [PATCH] unicode: add s_encoding null ptr check in utf8ncursor

[Eric Biggers]

On Wed, Sep 20, 2023 at 07:20:16PM +0800, Edward AD wrote:
> When init struct utf8cursor *u8c in utf8ncursor(), we need check um is
> valid.
> 
> Reported-and-tested-by: syzbot+9cf75dc581fb4307d6dd@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: b81427939590 ("ext4: remove redundant checks of s_encoding")
> Signed-off-by: Edward AD <twuufnxlz@xxxxxxxxx>
> ---
>  fs/unicode/utf8-norm.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/unicode/utf8-norm.c b/fs/unicode/utf8-norm.c
> index 768f8ab448b8..906b639b2f38 100644
> --- a/fs/unicode/utf8-norm.c
> +++ b/fs/unicode/utf8-norm.c
> @@ -422,6 +422,10 @@ int utf8ncursor(struct utf8cursor *u8c, const struct unicode_map *um,
>  {
>  	if (!s)
>  		return -1;
> +
> +	if (IS_ERR_OR_NULL(um))
> +		return -1;
> +
>  	u8c->um = um;
>  	u8c->n = n;
>  	u8c->s = s;
> -- 

See https://lore.kernel.org/linux-fsdevel/20230920073659.GC2739@sol.localdomain/

- Eric