From: Anastasia Belova <abelova@astralinux.ru>
To: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
lvc-project@linuxtesting.org
Subject: Re: [PATCH] mm/zsmalloc: prevent integer overflow in obj_free
Date: Thu, 20 Mar 2025 12:12:27 +0300 [thread overview]
Message-ID: <ad70d906-8889-40d3-9af6-6a2be68faf77@astralinux.ru> (raw)
In-Reply-To: <w7ralg6gzp6kuqwulpczs7uv4htllt2rasuto5unoy7xasr5cv@2z6pd7syyj6q>
On 3/13/25 5:42 PM, Sergey Senozhatsky wrote:
> On (25/03/13 14:51), Anastasia Belova wrote:
>> The result of multiplication of class_size and f_objidx
>> may not fit unsigned integer. Add explicit casting to
>> unsigned long to prevent integer overflow.
> I can't see how this can be possible. Neither size_class nor
> object idx can take values to cause mul overflow.
object index may be up to OBJ_INDEX_MASK = ((_AC(1, UL) <<
OBJ_INDEX_BITS) - 1)
= ((_AC(1, UL) << PAGE_SHIFT) - 1)
class_size may be up to ZS_MAX_ALLOC_SIZE = PAGE_SIZE.
If address (and unsigned long) is 64-bit, the result of multiplication
won't fit 32-bit integer. Please correct me if I'm wrong.
Best regards,
Anastasia Belova
next prev parent reply other threads:[~2025-03-20 9:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-13 11:51 Anastasia Belova
2025-03-13 14:42 ` Sergey Senozhatsky
2025-03-20 9:12 ` Anastasia Belova [this message]
2025-03-25 3:24 ` Sergey Senozhatsky
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