From: no-reply@sashiko.virtuozzo.com
To: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>,
Vasileios Almpanis <vasileios.almpanis@virtuozzo.com>,
Konstantin Khorenko <khorenko@virtuozzo.com>,
Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Cc: devel@openvz.org
Subject: Re: [Devel] [PATCH hci-8.1 1/2] mm/huge_memory: recheck a special PMD under the lock in copy_huge_pmd()
Date: Wed, 14 Oct 2026 17:07:06 +0000 [thread overview]
Message-ID: <010701a13b61c6e1-2f194f36-e7a4-45ec-b785-482d33790428-000000@eu-central-1.amazonses.com> (raw)
In-Reply-To: <20261014-b4-prep-khorenko-vstor-149847-1-upstream-fixes-v1-1-7fde9ffbebe9@virtuozzo.com>
> copy_huge_pmd() reads a special PMD without the page table lock and
> copies that value to the child. The mmap write lock held by fork does
> not stop unmap_mapping_range(): it zaps under i_mmap_rwsem and the PMD
> lock.
>
> The zap visits the parent VMA before the child's, as dup_mmap() links
> the child right after the parent in i_mmap. If it clears the parent PMD
> after fork has read it, and passes the child before fork copies it, the
> child keeps a mapping the driver has revoked:
>
> - vfio-pci: the child reaches the BAR after the device memory was
> disabled or the device was reset, instead of getting SIGBUS;
> - panthor: the child maps the pages of an evicted buffer object after
> they are freed.
>
> [ ... ]
> https://virtuozzo.atlassian.net/browse/VSTOR-150144
>
> Feature: fix ms/mm
> Assisted-by: LLM
> Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261014-b4-prep-khorenko-vstor-149847-1-upstream-fixes-v1-0-7fde9ffbebe9@virtuozzo.com?part=1
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next prev parent reply other threads:[~2026-10-14 17:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-14 17:03 [Devel] [PATCH hci-8.1 0/2] mm, binfmt_elf: two fixes also posted to mainline Konstantin Khorenko
2026-10-14 17:03 ` [Devel] [PATCH hci-8.1 1/2] mm/huge_memory: recheck a special PMD under the lock in copy_huge_pmd() Konstantin Khorenko
2026-10-14 17:07 ` no-reply [this message]
2026-10-14 17:03 ` [Devel] [PATCH hci-8.1 2/2] binfmt_elf: return the real error when program headers cannot be loaded Konstantin Khorenko
2026-10-14 17:07 ` no-reply
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