From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Lorenzo Stoakes <ljs@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Suren Baghdasaryan <surenb@google.com>,
"Liam R. Howlett" <liam@infradead.org>,
Vlastimil Babka <vbabka@kernel.org>,
Shakeel Butt <shakeel.butt@linux.dev>,
Mike Rapoport <rppt@kernel.org>, Michal Hocko <mhocko@suse.com>,
Uladzislau Rezki <urezki@gmail.com>,
Toshi Kani <toshi.kani@hpe.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Kiryl Shutsemau <kas@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Dev Jain <dev.jain@arm.com>,
Ryan Roberts <ryan.roberts@arm.com>
Cc: David Carlier <devnexen@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
stable@vger.kernel.org,
syzbot+fd95a72470f5a44e464c@syzkaller.appspotmail.com
Subject: Re: [PATCH mm-hotfixes v3 1/4] mm/vmalloc: acquire init_mm lock on huge vmap to avoid ptdump UAF
Date: Thu, 16 Jul 2026 12:00:54 +0200 [thread overview]
Message-ID: <45c4a73b-d0a1-4f66-8bfc-da1e78cdc50a@kernel.org> (raw)
In-Reply-To: <d3b07e20-fa35-41c7-ac40-11614f7a3b2e@kernel.org>
On 7/16/26 11:53, David Hildenbrand (Arm) wrote:
>
>>
>> #define CREATE_TRACE_POINTS
>> #include <trace/events/vmalloc.h>
>> @@ -158,10 +159,25 @@ static int vmap_try_huge_pmd(pmd_t *pmd, unsigned long addr, unsigned long end,
>> if (!IS_ALIGNED(phys_addr, PMD_SIZE))
>> return 0;
>>
>> - if (pmd_present(*pmd) && !pmd_free_pte_page(pmd, addr))
>> - return 0;
>> + if (!pmd_present(*pmd))
>> + return pmd_set_huge(pmd, phys_addr, prot);
>>
>> - return pmd_set_huge(pmd, phys_addr, prot);
>> + /*
>> + * Kernel page table walkers either walk ranges they own exclusively or
>> + * hold the mmap write lock on init_mm (ptdump being the motivating
>> + * case).
>> + *
>> + * Therefore, acquire the mmap read lock to prevent use-after-free when
>> + * freeing page tables.
>> + */
>
> Can you spell out here why arm64 is special?
>
Nevermind, I spotted #4.
Thanks!
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
next prev parent reply other threads:[~2026-07-16 10:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-14 17:24 [PATCH mm-hotfixes v3 0/4] mm: fix UAF caused by race between ptdump and vmap pgtable freeing Lorenzo Stoakes
2026-07-14 17:24 ` [PATCH mm-hotfixes v3 1/4] mm/vmalloc: acquire init_mm lock on huge vmap to avoid ptdump UAF Lorenzo Stoakes
2026-07-15 10:34 ` Kiryl Shutsemau
2026-07-15 14:16 ` Lorenzo Stoakes (ARM)
2026-07-15 19:14 ` Andrew Morton
2026-07-16 9:54 ` Lorenzo Stoakes (ARM)
2026-07-16 9:53 ` David Hildenbrand (Arm)
2026-07-16 10:00 ` David Hildenbrand (Arm) [this message]
2026-07-14 17:24 ` [PATCH mm-hotfixes v3 2/4] x86/mm/pat: acquire mmap lock on page table free " Lorenzo Stoakes
2026-07-14 17:29 ` Dave Hansen
2026-07-15 8:49 ` Lorenzo Stoakes (ARM)
2026-07-15 15:24 ` Will Deacon
2026-07-15 15:49 ` Mike Rapoport
2026-07-16 10:06 ` Lorenzo Stoakes (ARM)
2026-07-16 11:31 ` Will Deacon
2026-07-16 13:29 ` Lorenzo Stoakes (ARM)
2026-07-16 9:55 ` David Hildenbrand (Arm)
2026-07-14 17:24 ` [PATCH mm-hotfixes v3 3/4] mm/ptdump: always stabilise against page table freeing using init_mm Lorenzo Stoakes
2026-07-15 10:36 ` Kiryl Shutsemau
2026-07-16 9:59 ` David Hildenbrand (Arm)
2026-07-14 17:24 ` [PATCH mm-hotfixes v3 4/4] arm64: remove redundant concurrent ptdump UAF mitigation Lorenzo Stoakes
2026-07-16 10:00 ` David Hildenbrand (Arm)
2026-07-14 17:31 ` [PATCH mm-hotfixes v3 0/4] mm: fix UAF caused by race between ptdump and vmap pgtable freeing Dave Hansen
2026-07-15 7:28 ` Lorenzo Stoakes (ARM)
2026-07-14 19:11 ` Andrew Morton
2026-07-15 8:31 ` Lorenzo Stoakes (ARM)
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