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Mon, 16 Oct 2023 08:53:11 -0700 (PDT) MIME-Version: 1.0 References: <20231016153446.132763-1-pedro.falcato@gmail.com> In-Reply-To: <20231016153446.132763-1-pedro.falcato@gmail.com> From: Alexander Potapenko Date: Mon, 16 Oct 2023 17:52:29 +0200 Message-ID: Subject: Re: [PATCH v2] mm: kmsan: Panic on failure to allocate early boot metadata To: Pedro Falcato Cc: kasan-dev@googlegroups.com, Marco Elver , Dmitry Vyukov , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: EEBCBA0008 X-Stat-Signature: e38ej4g93xjz8wp5ckbmwmoc95pu15wu X-Rspam-User: X-HE-Tag: 1697471592-738287 X-HE-Meta: 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 93lJ01mY eIic8kF4fNq5HtgawE+aW+QUcnsQJJnurogQvz2OaWbMDmtaT2KwAYacoDM56K2SKthrKevNuAifKkWV6vkxpNliB9Z4whGGwv08ezSqKhZDXIHACid1OqI8wHY+Oq6XRh1CH8DtLnBwabBRJTGXWvRWOoMTEIkV+BCP48ffntPi9jEDS3Or5Ea9hhIlH4W/w6uXEbnhJLbHU/OOQXiBHILYCyamyEPwhICyT1rf8DTK12GBEgU+6zXfAM8RGS2dMybtI8B6yQBrMDAatEB2hmqwc54+rcbNCsguKnK9FeU4mGDkd8vMoATdLneqriMkbwzE4DUKDboKyOzm0nI8wot8bnw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.089643, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 16, 2023 at 5:34=E2=80=AFPM Pedro Falcato wrote: > > Given large enough allocations and a machine with low enough memory (i.e > a default QEMU VM), it's entirely possible that > kmsan_init_alloc_meta_for_range's shadow+origin allocation fails. > > Instead of eating a NULL deref kernel oops, check explicitly for > memblock_alloc() failure and panic with a nice error message. For posterity, it is generally quite important for the allocated shadow and origin to be contiguous, otherwise an unaligned memory write may result in memory corruption (the corresponding unaligned shadow write will be assuming that shadow pages are adjacent). So instead of panicking we could have split the range into smaller ones until the allocation succeeds, but that would've led to hard-to-debug problems in the future. > > Signed-off-by: Pedro Falcato Reviewed-by: Alexander Potapenko