From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Rosen Penev <rosenp@gmail.com>
Cc: Alex Williamson <alex@shazbot.org>,
kvm@vger.kernel.org, Kees Cook <kees@kernel.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
open list <linux-kernel@vger.kernel.org>,
open "list:KERNEL" HARDENING "(not" covered by other
"areas):Keyword:b__counted_by(_le|_be)?b"
<linux-hardening@vger.kernel.org>,
Leon Romanovsky <leon@kernel.org>
Subject: Re: [PATCH] vfio: pci: use kzalloc_flex
Date: Mon, 30 Mar 2026 18:51:01 -0600 [thread overview]
Message-ID: <e5207fad-2235-4849-b238-c85ee62508bf@embeddedor.com> (raw)
In-Reply-To: <CAKxU2N_o=x=wSjiQqyB68VvhxP_ZoGoSyQagKm=0BdKkgrmPnw@mail.gmail.com>
>>>>> Use __counted_by for extra runtime analysis. Move assignment to after
>>>>> allocation as required by __counted_by.
>>>>
>>>> I don't understand this statement, nr_ranges was previously set after
>>>> the allocation of phys_vec. The only reordering was relative to
>>>> setting vdev, but that appears arbitrary.
>>> Yes that one. My understanding is __counted_by mandates immediate
>>> assignment after allocation. Otherwise UBSAN complains.
>>
>> Not true. However, it's best practice.
>>
>> The requirement is that the _counter_ must be initialized before
>> the first reference to the flexible-array member.
> OTOH kzalloc_flex automatically sets it for GCC15 and above. Useful to
That's what the "it's best practice." comment above alludes to.
-Gustavo
next prev parent reply other threads:[~2026-03-31 0:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-26 2:37 [PATCH] vfio: pci: use kzalloc_flex Rosen Penev
2026-03-30 22:19 ` Alex Williamson
2026-03-30 23:24 ` Rosen Penev
2026-03-30 23:46 ` Gustavo A. R. Silva
2026-03-31 0:18 ` Rosen Penev
2026-03-31 0:51 ` Gustavo A. R. Silva [this message]
2026-03-31 0:23 ` Alex Williamson
2026-03-31 5:11 ` Leon Romanovsky
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