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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745485912; bh=15vRsUE0bDXeqQTgh2kUDIT+VRozCY31BdgeStUR/M8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dIOomLFTA32COw9i8Mv1mpV5Y4V63i1JGQc6qx8dJ9njwQwWpAnkL6ThhOAtCg8dH 2fQmcOS9B80t5Q8s9cFqB/tTu/9iOKjsfDL8VUzoLss+2r2Zb5bDLwNo5DwcW9nipx RoY4qWXhiK8btBDAeFRWR0T28PeS8qITapO12PN6HIPz8m+hqGienY+sr9k9X/etyb oU0tmOKsdEG/X7IimcgLEsJiWKxM7ULVhBZkvHVsG3kKnLW3obx2Wq6QMn5y5PheDn pdr0glpa1vkwoxidfVrxXaMYlGlBS5kpimxy1ISQNcihWrQmTeqSyvjO7Lh8JVNFvm hakoQIDL9XSuw== Date: Thu, 24 Apr 2025 11:11:47 +0200 From: Danilo Krummrich To: Kees Cook Cc: Andrew Morton , Erhard Furtner , Michal Hocko , Vlastimil Babka , Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] mm: vmalloc: Support more granular vrealloc() sizing Message-ID: References: <20250424023119.work.333-kees@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250424023119.work.333-kees@kernel.org> X-Rspamd-Queue-Id: 1C7C818000B X-Stat-Signature: fz6zspy6rdzh1ghm9ario5iiygho4c9p X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1745485913-422915 X-HE-Meta: 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 4tk/XsBC m1JqgWq7DmZTmMOHLlffYDMf1kH1ecxQJnSMuP9tYmByizKzQSPzkgdiAF2dfhHRZqQhGrZuv3rVh307qAoSsPfaOnjE1Ftk1Xkl2/Fpv6XosZWIEcIWmFA4SvWwHV+mVZR6xLisf+B7yhA8rOdCq/ER/7TJU2lqXuSLdExXQETq+QWBSiBE2ROZo/4fFzrUEoVeaHo2hb5HXoNyaga6ylZUYVN9sqUv31Ei+zbp3GYW2Z7nAgmioSkh9ZNTpq57NCW8L0eKp7pAwNutuXQbIQmFF7tRZdUeYs/eBOzWQELfDJF/9kRHC4M8DFjsawyq6Sr8cOhQ6nxdX8/s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 23, 2025 at 07:31:23PM -0700, Kees Cook wrote: > Introduce struct vm_struct::requested_size so that the requested > (re)allocation size is retained separately from the allocated area > size. This means that KASAN will correctly poison the correct spans > of requested bytes. This also means we can support growing the usable > portion of an allocation that can already be supported by the existing > area's existing allocation. > > Reported-by: Erhard Furtner > Closes: https://lore.kernel.org/all/20250408192503.6149a816@outsider.home/ > Fixes: 3ddc2fefe6f3 ("mm: vmalloc: implement vrealloc()") > Signed-off-by: Kees Cook Good catch! One question below, otherwise Reviewed-by: Danilo Krummrich > @@ -4088,14 +4093,27 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) > * would be a good heuristic for when to shrink the vm_area? > */ > if (size <= old_size) { > - /* Zero out spare memory. */ > - if (want_init_on_alloc(flags)) > + /* Zero out "freed" memory. */ > + if (want_init_on_free()) > memset((void *)p + size, 0, old_size - size); > + vm->requested_size = size; > kasan_poison_vmalloc(p + size, old_size - size); > kasan_unpoison_vmalloc(p, size, KASAN_VMALLOC_PROT_NORMAL); > return (void *)p; > } > > + /* > + * We already have the bytes available in the allocation; use them. > + */ > + if (size <= alloced_size) { > + kasan_unpoison_vmalloc(p, size, KASAN_VMALLOC_PROT_NORMAL); > + /* Zero out "alloced" memory. */ > + if (want_init_on_alloc(flags)) > + memset((void *)p + old_size, 0, size - old_size); > + vm->requested_size = size; > + kasan_poison_vmalloc(p + size, alloced_size - size); Do we need this? We know that old_size < size <= alloced_size. And since previously [p + old_size, p + alloced_size) must have been poisoned, [p + size, p + alloced_size) must be poisoned already? Maybe there was a reason, since in the above (size <= old_size) case kasan_unpoison_vmalloc() seems unnecessary too.