linux-kernel - Re: [PATCH] Fix wrong max check in bch2_opt

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Message-ID: <pkxqQnSTQLReyYEHegx90LNp5dbR6LlpcqUIkBFa2CiL-0P48QWpGJ1YYKtWwu0IFM7H-2T4fYQz0MldP6OqZppPzmqafQDKouhETLnM5o4=@proton.me>
Date: Wed, 06 Nov 2024 08:11:13 +0000
From: Piotr Zalewski <pZ010001011111@...ton.me>
To: Piotr Zalewski <pZ010001011111@...ton.me>
Cc: kent.overstreet@...ux.dev, linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, skhan@...uxfoundation.org, syzbot+bee87a0c3291c06aa8c6@...kaller.appspotmail.com
Subject: Re: [PATCH] Fix wrong max check in bch2_opt_validate

Hi Kent,

Did you see this?

Best regards

On Friday, November 1st, 2024 at 12:22 AM, Piotr Zalewski <pZ010001011111@...ton.me> wrote:

> Use opt->max-1 in bch2_opt_validate when option type is BCH_OPT_STR. When
>
> option type is BCH_OPT_STR, real option's max is one less than the max
> value stored in option structure.
>
> Reported-by: syzbot+bee87a0c3291c06aa8c6@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=bee87a0c3291c06aa8c6
> Fixes: 63c4b2545382 ("bcachefs: Better superblock opt validation")
> Signed-off-by: Piotr Zalewski pZ010001011111@...ton.me
>
> ---
> fs/bcachefs/opts.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/bcachefs/opts.c b/fs/bcachefs/opts.c
> index 83f55cf99d46..bffcbe6a6fd0 100644
> --- a/fs/bcachefs/opts.c
> +++ b/fs/bcachefs/opts.c
> @@ -290,6 +290,8 @@ static int bch2_mount_opt_lookup(const char *name)
>
> int bch2_opt_validate(const struct bch_option *opt, u64 v, struct printbuf *err)
> {
> + const u64 opt_max = opt->type == BCH_OPT_STR ? opt->max - 1 : opt->max;
>
> +
> if (v < opt->min) {
>
> if (err)
> prt_printf(err, "%s: too small (min %llu)",
> @@ -297,10 +299,10 @@ int bch2_opt_validate(const struct bch_option *opt, u64 v, struct printbuf *err)
> return -BCH_ERR_ERANGE_option_too_small;
> }
>
> - if (opt->max && v >= opt->max) {
>
> + if (opt->max && v >= opt_max) {
>
> if (err)
> prt_printf(err, "%s: too big (max %llu)",
> - opt->attr.name, opt->max);
>
> + opt->attr.name, opt_max);
>
> return -BCH_ERR_ERANGE_option_too_big;
> }
>
> --
> 2.47.0
>