From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BEA33212B2F for ; Thu, 5 Feb 2026 14:51:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770303061; cv=none; b=qIsBAKkwpbMttmUkSU7TmR2nPPJWZ7u8mxnZ3nEMXq0+XNxM1rO5WQAhOpzMbUQJrcCRv9Tq9Nu9C8MJYsksFamc/qP/AcjXm/p/+ZW6UolupI0nKHcBvqtlTk3hi56VfNLFWlQ84RdZ6qQ3ZPCt6VK9YMKGeLq3mNUel8Nek8A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770303061; c=relaxed/simple; bh=YVgxEMUekUiwSH1AJnQti1nrs2UQrYUrvGEBctUtEHI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=l1Wl++nbdmmwLbm6WzJYWpYGim9q4OMVI3egQWsek1lUEEAYkdi5DS9ZLgtHgZIqDs/Ope6PTB31iLTXJxBCY2Bep6u1glGcTs0qf7KoYt2a18A3JJBJTUktBCzZ5ozIWuOqhqY96S6JP3hOvrUc09gVDl2PGpXE3MaYmcicS2s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--pimyn.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=qPPgp+Db; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--pimyn.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="qPPgp+Db" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-47edf8ba319so18286345e9.2 for ; Thu, 05 Feb 2026 06:51:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1770303059; x=1770907859; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Uvp9ADJW+h5hQnGxgLtc+vFKCRET1FtUQ5XB5iZCpDw=; b=qPPgp+DbURDEFVm6I8QQrWAIR4WHmD5oh1KOtLJIV88YsOBb/nf68eu6p9hJx/KbTd WGtxU87SRWz3DXd7KYEGDTB6R2l4xODH+x7VT0S175xb3UX/Q2fc4s0mun/bk67FAn+6 hmI3CU1+sQTo6jZ8M/CMVitoCMzBiSGbdP+Ntc74PbEnL8vU7z3i7oPuAywRYrHg1ihl kTGL1f24zRfVB7KQ37gmAzGfxktt5sgf2Qdj92ZsRJPeEQh0egl4226yl9wk00CAonM4 zZk+EajYW1qmQHG0UC4zfh2oooTomqcfIKYEGw7P2gjBFFT9wMrNzlF3O+XbFyrESQqN QHRg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770303059; x=1770907859; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Uvp9ADJW+h5hQnGxgLtc+vFKCRET1FtUQ5XB5iZCpDw=; b=ZePSd+BY84HGHRhKd8wjeqVGXheNNbLmTtgEsqG6M4hhZwL06fDEpSdJ7/EQwKfXHX +F3T+5Gnx/9PwcLyVBsAzWnUbWdMKPcgo3iRee4dln4+oBIdrENECoQDUmMzMUzrmIkX bh5ewqMWoKJOpSVIGYG5xC0gzgKkUkMVvd8JjF3XUgKZtE3bd5JyyUzWZYSyNCJqA+lR bdj/c7ON/gwWdhUc87RY5QgE1A03pYRkPPzsHP0MFL0oEy+W4mgQcRTapeD1Wj05xwZl XjV9EzNbkdBv5tRlS/sHac/l3grq0mLGQtTAPsNzQ8gCriMlsCz60EwtC3Dle9mvMAnr 2q3w== X-Gm-Message-State: AOJu0Yz0/qL1BxrjNsqADntlkbTUym5bcSfNj/yw7F6iMMiu49s/+Kl8 WwS7CN1EQA2wkL92S5MK23CDJJ4QbG0oHRbBNdpuNiE/atuOJs8J6v26ac/P0Hw/+2Fw7S+Whbf CHafAeIbjkeshva8BEFJSzIJsVPLrONbzwqzAM12Cq9NqLx8vI7f7zxdMFmfNCnEBe1w0X1tF2D 0NXJUbIPLIneIC+F6V0OdlrNh7bYAwcPw= X-Received: from wmbg27.prod.google.com ([2002:a05:600c:a41b:b0:480:692a:4431]) (user=pimyn job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:6212:b0:479:1348:c614 with SMTP id 5b1f17b1804b1-4830e9707bbmr86569595e9.26.1770303059112; Thu, 05 Feb 2026 06:50:59 -0800 (PST) Date: Thu, 5 Feb 2026 15:50:55 +0100 In-Reply-To: <2026020339-trickery-vegan-e9c3@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <2026020339-trickery-vegan-e9c3@gregkh> X-Mailer: git-send-email 2.53.0.rc2.204.g2597b5adb4-goog Message-ID: <20260205145055.3333340-1-pimyn@google.com> Subject: [PATCH 5.15.y v3] mm/kfence: randomize the freelist on initialization From: Pimyn Girgis To: stable@vger.kernel.org Cc: Pimyn Girgis , Alexander Potapenko , Dmitry Vyukov , Marco Elver , Ernesto Martnez Garca , Greg KH , Kees Cook , Andrew Morton Content-Type: text/plain; charset="UTF-8" Randomize the KFENCE freelist during pool initialization to make allocation patterns less predictable. This is achieved by shuffling the order in which metadata objects are added to the freelist using get_random_u32_below(). Additionally, ensure the error path correctly calculates the address range to be reset if initialization fails, as the address increment logic has been moved to a separate loop. Link: https://lkml.kernel.org/r/20260120161510.3289089-1-pimyn@google.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Pimyn Girgis Reviewed-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: Marco Elver Cc: Ernesto Martnez Garca Cc: Greg KH Cc: Kees Cook Cc: Signed-off-by: Andrew Morton (cherry picked from commit 870ff19251bf3910dda7a7245da826924045fedd) Signed-off-by: Pimyn Girgis --- v2: handle addr calculation for error path within appropriate loop --- mm/kfence/core.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index c49bc76b3a38..e1a555eeec45 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -520,7 +520,7 @@ static bool __init kfence_init_pool(void) { unsigned long addr = (unsigned long)__kfence_pool; struct page *pages; - int i; + int i, rand; char *p; if (!__kfence_pool) @@ -576,13 +576,30 @@ static bool __init kfence_init_pool(void) INIT_LIST_HEAD(&meta->list); raw_spin_lock_init(&meta->lock); meta->state = KFENCE_OBJECT_UNUSED; - meta->addr = addr; /* Initialize for validation in metadata_to_pageaddr(). */ - list_add_tail(&meta->list, &kfence_freelist); + /* Use addr to randomize the freelist. */ + meta->addr = i; /* Protect the right redzone. */ - if (unlikely(!kfence_protect(addr + PAGE_SIZE))) + if (unlikely(!kfence_protect(addr + 2 * i * PAGE_SIZE + PAGE_SIZE))) { + addr += 2 * i * PAGE_SIZE; goto err; + } + } + + for (i = CONFIG_KFENCE_NUM_OBJECTS; i > 0; i--) { + rand = get_random_u32() % i; + swap(kfence_metadata[i - 1].addr, kfence_metadata[rand].addr); + } + for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) { + struct kfence_metadata *meta_1 = &kfence_metadata[i]; + struct kfence_metadata *meta_2 = &kfence_metadata[meta_1->addr]; + + list_add_tail(&meta_2->list, &kfence_freelist); + } + + for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) { + kfence_metadata[i].addr = addr; addr += 2 * PAGE_SIZE; } -- 2.53.0.rc2.204.g2597b5adb4-goog