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Date:   Wed, 20 Sep 2023 12:37:06 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Edward AD <twuufnxlz@gmail.com>
Cc:     syzbot+9cf75dc581fb4307d6dd@syzkaller.appspotmail.com,
        adilger.kernel@dilger.ca, krisman@collabora.com,
        linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        tytso@mit.edu
Subject: Re: [PATCH] unicode: add s_encoding null ptr check in utf8ncursor
Message-ID: <20230920193706.GB914@sol.localdomain>
References: <0000000000001f0b970605c39a7e@google.com>
 <20230920112015.829124-2-twuufnxlz@gmail.com>
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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@syzkaller.appspotmail.com
> Fixes: b81427939590 ("ext4: remove redundant checks of s_encoding")
> Signed-off-by: Edward AD <twuufnxlz@gmail.com>
> ---
>  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