linux-hardening - Re: [PATCH] pstore: ram_core: fix possible overflow in persistent_ram_init

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Message-Id: <170155004188.180877.9632245955503394490.b4-ty@chromium.org>
Date: Sat,  2 Dec 2023 12:47:23 -0800
From: Kees Cook <keescook@...omium.org>
To: Tony Luck <tony.luck@...el.com>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	linux-hardening@...r.kernel.org,
	Sergey Shtylyov <s.shtylyov@....ru>
Cc: Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] pstore: ram_core: fix possible overflow in persistent_ram_init_ecc()

On Sun, 05 Nov 2023 23:29:36 +0300, Sergey Shtylyov wrote:
> In persistent_ram_init_ecc(), on 64-bit arches DIV_ROUND_UP() will return
> 64-bit value since persistent_ram_zone::buffer_size has type size_t which
> is derived from the 64-bit *unsigned long*, while the ecc_blocks variable
> this value gets assigned to has (always 32-bit) *int* type.  Even if that
> value fits into *int* type, an overflow is still possible when calculating
> the size_t typed ecc_total variable further below since there's no cast to
> any 64-bit type before multiplication.  Declaring the ecc_blocks variable
> as *unsigned long* should fix this mess...
> 
> [...]

I changed this from unsigned long to size_t, which will do the same thing.

Applied to for-linus/pstore, thanks!

[1/1] pstore: ram_core: fix possible overflow in persistent_ram_init_ecc()
      https://git.kernel.org/kees/c/c92116e01d32

Take care,

-- 
Kees Cook