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

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Date: Sun, 3 Dec 2023 11:59:52 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	<linux-hardening@...r.kernel.org>
Subject: Re: [PATCH] pstore: ram_core: fix possible overflow in
 persistent_ram_init_ecc()

On 12/2/23 11:47 PM, Kees Cook 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.

   Not quite the same. And ecc_blocks is a block count, not a byte count, so
size_t doesn't seem appropriate...

> 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,

   Thanks anyway. :-)

MBR, Sergey