From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3DCDE1AB505; Mon, 14 Oct 2024 15:11:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728918697; cv=none; b=mHANOub6DpFXrBd9NmhGuYtHTqJVH68eFrmBb260IM2B7vVwvOSVDRV4F62QJIvxvljxwDivUK8EzrT/tqlRq5tUL6dg7DzwcNPXwniicerQipVRGnFvSLzfogrMnnK4DDaMJr23rGPGYIBsj9WelYXn4hla5sCrRQia9vg8znM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728918697; c=relaxed/simple; bh=byVFIa3benGbb/Y2NQP016wKMkTGZyAKAwlxU94Z6p4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BPsMIqrk8HHpNPCCpao9NJ1Hc5cYplFz0ZcfQtKEBHQ66iR4CLmP5hLNXFaGwnClmvsIjpaRbcnxgbW+GuaWEen+AloOva00LfY9JuSWzHSV+0/QUDeEwQrEoPIehtMwMyoCpdvgRVwC31Eu7CADLwxADRzDN012LvEdrXIUR8A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hSOengrW; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="hSOengrW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E22CC4CEC3; Mon, 14 Oct 2024 15:11:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1728918697; bh=byVFIa3benGbb/Y2NQP016wKMkTGZyAKAwlxU94Z6p4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hSOengrWnIG1GGRPmGnzWVYnnyJV6JvndKE3x0J3PU806IELjeC7m5ZiXkLAwK9es cKD4/Ghg6AoBwQnGHbY/sHRY6V09MOMdOL+mqGHuXUnmsbz7jNQSSDOkQ1ArzkwOE8 PkAN2ypIUM93gtu//IZxeEI+XaalxYBopF3VfJVU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Gow , Kees Cook , Alexandre Ghiti , Linus Walleij , Luis Chamberlain , Mark Rutland , Russell King , Andrew Morton Subject: [PATCH 6.1 365/798] mm: only enforce minimum stack gap size if its sensible Date: Mon, 14 Oct 2024 16:15:19 +0200 Message-ID: <20241014141232.289077513@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241014141217.941104064@linuxfoundation.org> References: <20241014141217.941104064@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Gow commit 69b50d4351ed924f29e3d46b159e28f70dfc707f upstream. The generic mmap_base code tries to leave a gap between the top of the stack and the mmap base address, but enforces a minimum gap size (MIN_GAP) of 128MB, which is too large on some setups. In particular, on arm tasks without ADDR_LIMIT_32BIT, the STACK_TOP value is less than 128MB, so it's impossible to fit such a gap in. Only enforce this minimum if MIN_GAP < MAX_GAP, as we'd prefer to honour MAX_GAP, which is defined proportionally, so scales better and always leaves us with both _some_ stack space and some room for mmap. This fixes the usercopy KUnit test suite on 32-bit arm, as it doesn't set any personality flags so gets the default (in this case 26-bit) task size. This test can be run with: ./tools/testing/kunit/kunit.py run --arch arm usercopy --make_options LLVM=1 Link: https://lkml.kernel.org/r/20240803074642.1849623-2-davidgow@google.com Fixes: dba79c3df4a2 ("arm: use generic mmap top-down layout and brk randomization") Signed-off-by: David Gow Reviewed-by: Kees Cook Cc: Alexandre Ghiti Cc: Linus Walleij Cc: Luis Chamberlain Cc: Mark Rutland Cc: Russell King Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/util.c +++ b/mm/util.c @@ -399,7 +399,7 @@ static unsigned long mmap_base(unsigned if (gap + pad > gap) gap += pad; - if (gap < MIN_GAP) + if (gap < MIN_GAP && MIN_GAP < MAX_GAP) gap = MIN_GAP; else if (gap > MAX_GAP) gap = MAX_GAP;