From: Dave Hansen <dave.hansen@intel.com>
To: Yuntao Wang <ytcoode@gmail.com>
Cc: bhe@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
hpa@zytor.com, kirill@shutemov.name,
linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com,
peterz@infradead.org, stable@vger.kernel.org, tglx@linutronix.de,
x86@kernel.org
Subject: Re: [PATCH] x86/mm: Fix possible index overflow when creating page table mapping
Date: Thu, 16 Jun 2022 07:20:40 -0700 [thread overview]
Message-ID: <8e2c9b2b-d8ad-5e9a-7aa6-23e0c599c2e9@intel.com> (raw)
In-Reply-To: <20220616141525.1790083-1-ytcoode@gmail.com>
On 6/16/22 07:15, Yuntao Wang wrote:
> On Thu, 16 Jun 2022 07:02:56 -0700, Dave Hansen wrote:
>> On 6/16/22 06:55, Yuntao Wang wrote:
>>> There are two issues in phys_p4d_init():
>>>
>>> - The __kernel_physical_mapping_init() does not do boundary-checking for
>>> paddr_end and passes it directly to phys_p4d_init(), phys_p4d_init() does
>>> not do bounds checking either, so if the physical memory to be mapped is
>>> large enough, 'p4d_page + p4d_index(vaddr)' will wrap around to the
>>> beginning entry of the P4D table and its data will be overwritten.
>>>
>>> - The for loop body will be executed only when 'vaddr < vaddr_end'
>>> evaluates to true, but if that condition is true, 'paddr >= paddr_end'
>>> will evaluate to false, thus the 'if (paddr >= paddr_end) {}' block will
>>> never be executed and become dead code.
>> Could you explain a bit how you found this? Was this encountered in
>> practice and debugged or was it found by inspection?
> I found it by inspection.
Dare I ask how this was tested?
next prev parent reply other threads:[~2022-06-16 14:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-16 13:55 [PATCH] x86/mm: Fix possible index overflow when creating page table mapping Yuntao Wang
2022-06-16 14:02 ` Dave Hansen
2022-06-16 14:15 ` Yuntao Wang
2022-06-16 14:20 ` Dave Hansen [this message]
2022-06-17 6:38 ` Yuntao Wang
2022-06-18 0:22 ` Kirill A. Shutemov
2022-06-18 2:08 ` Yuntao Wang
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