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bh=y5iTm0qa00qIrnZejVeX3Ab8YTjp2BAj50nhyhXZ9E4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GlYj4bdUgtKWdopH5Pm0KQqKQLoi5ebsh9SGDJPFtGS/tq0yzDFb/xQRJ6XDphmK2 AbTtexUtTLD0iK1DTbQ9RISyVa2NU9xYPZI8c28vBG/aAYjxOWJML3zIHT8TxriRGf 1zqyN/7ef1sPBXRes3tezLn0+rvGzaWWm2zaIeavxcitwcufirPgsCLMKPAJQVh85U tXMspr70v5LARinfIxDEK4GPz9uLenK3ElOcAaYSGaibfeTBJ2dlLRKKuCBGp1hZVC eAbYZUt/JqjLCxexwFPYdZztazWyfYVUz1qDbv8PZKFbirA0NYfx/Y09rpz+cTo6q6 t17EaUkC9zyVQ== From: Kees Cook To: Andrew Morton Cc: Kees Cook , Pawan Gupta , Uladzislau Rezki , linux-mm@kvack.org, Shung-Hsi Yu , Eduard Zingerman , Erhard Furtner , Danilo Krummrich , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH 2/2] mm: vmalloc: Only zero-init on vrealloc shrink Date: Thu, 15 May 2025 14:42:16 -0700 Message-Id: <20250515214217.619685-2-kees@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250515214020.work.519-kees@kernel.org> References: <20250515214020.work.519-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; 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Fixes: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing") Tested-by: Pawan Gupta Signed-off-by: Kees Cook --- Cc: Andrew Morton Cc: Uladzislau Rezki Cc: --- mm/vmalloc.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 74bd00fd734d..00cf1b575c89 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4093,8 +4093,8 @@ 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 "freed" memory. */ - if (want_init_on_free()) + /* Zero out "freed" memory, potentially for future realloc. */ + if (want_init_on_free() || want_init_on_alloc(flags)) memset((void *)p + size, 0, old_size - size); vm->requested_size = size; kasan_poison_vmalloc(p + size, old_size - size); @@ -4107,9 +4107,11 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) if (size <= alloced_size) { kasan_unpoison_vmalloc(p + old_size, size - old_size, KASAN_VMALLOC_PROT_NORMAL); - /* Zero out "alloced" memory. */ - if (want_init_on_alloc(flags)) - memset((void *)p + old_size, 0, size - old_size); + /* + * No need to zero memory here, as unused memory will have + * already been zeroed at initial allocation time or during + * realloc shrink time. + */ vm->requested_size = size; return (void *)p; } -- 2.34.1