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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Rasmus Villemoes <ravi@prevas.dk>,
	Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jiri Slaby <jirislaby@kernel.org>,
	Bartosz Golaszewski <brgl@bgdev.pl>,  Kees Cook <kees@kernel.org>,
	Andy Shevchenko <andy@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	 linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@linaro.org>,
	stable@vger.kernel.org
Subject: Re: [PATCH] lib: string_helpers: fix potential snprintf() output truncation
Date: Tue, 22 Oct 2024 10:30:18 -0400	[thread overview]
Message-ID: <fae2751f6881bfc402a074e909be6a67ef9467df.camel@HansenPartnership.com> (raw)
In-Reply-To: <87y12gp7xb.fsf@prevas.dk>

On Tue, 2024-10-22 at 15:46 +0200, Rasmus Villemoes wrote:
[...]
> -       snprintf(buf, len, "%u%s %s", (u32)size,
> -                tmp, unit);
> +       if (j)
> +               snprintf(buf, len, "%u.%03u %s", (u32)size,
> remainder, unit);
> +       else
> +               snprintf(buf, len, "%u %s", (u32)size, unit);
>  }
>  EXPORT_SYMBOL(string_get_size);

Where are you getting this from?  The current statement you'd be
replacing is

	return snprintf(buf, len, "%u%s%s%s%s", (u32)size, tmp,
			(units & STRING_UNITS_NO_SPACE) ? "" : " ",
			unit,
			(units & STRING_UNITS_NO_BYTES) ? "" : "B");

The use of a tmp buffer prevents that having to be repeated.

If we had a way of specifying "ignore argument" I suppose we could
switch the format string on J and then only have a single statement.

Regards,

James


  reply	other threads:[~2024-10-22 14:30 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-21 10:04 Bartosz Golaszewski
2024-10-21 10:05 ` Bartosz Golaszewski
2024-10-22  7:15 ` Jiri Slaby
2024-10-22  7:30   ` Bartosz Golaszewski
2024-10-22  9:18     ` Andy Shevchenko
2024-10-22 11:07     ` David Laight
2024-10-22  9:15   ` Andy Shevchenko
2024-10-22 13:46     ` Rasmus Villemoes
2024-10-22 14:30       ` James Bottomley [this message]
  -- strict thread matches above, loose matches on Subject: below --
2024-10-21  9:14 Bartosz Golaszewski
2024-10-21  9:25 ` Andy Shevchenko
2024-10-21  9:34 ` Greg KH
2024-10-21  9:36   ` Bartosz Golaszewski
2024-10-21  9:50     ` Greg KH

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