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 562F91F472F; Wed, 6 Nov 2024 13:03:53 +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=1730898233; cv=none; b=XBeGk53UEPFTpJ1TwgKSS/K51MIRgS/ReVomjaCGCgZE8Fr4tyZtKjyO6IT8VMGDw5ZE5oP/mmhRz180d/W8Ud99/9snLB7q7MkZ3lT87SdG41SW37JE9nZmB0FVgBGAe6/jwzL5WhC7qywpDl0YiW732bxQ3pPur9czMLo/kKE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730898233; c=relaxed/simple; bh=midi08vshezM5vbL3hDmsI77uDNYLv8VSAGbzivVjpU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=a5Bmc1TqOfGfv3dRf4o/R0ANCIicn2RXKR6AG+XV7TeolTm1NLDtJs5UWduSXl+alVby+Y8qOLkDdW1zTUXvwqY6dGWtHMzhAa3rYqWud2ImY+vBGJWgW32Al9ltUnehL5I6jZ29qduP8v5urGUJ6KqalP73aXHVfPPrIRhPSaw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TtP3yxLz; 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="TtP3yxLz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF0A5C4CECD; Wed, 6 Nov 2024 13:03:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730898233; bh=midi08vshezM5vbL3hDmsI77uDNYLv8VSAGbzivVjpU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TtP3yxLz+0tiWqtMIkPDKbVQh/+SHv7QERQZCVidfVrWEl1zs0vfPG/04lVwMq/ei +BEsV30ALaI0EAUayOS1IwR4fduVGCCXeqWkUseEB3GT6qiqb3RChq2hcJRYaoFfj2 +xtdewAPu97BD1LKCbm3nCC4c0+d8sa6IuHRv4G4= 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 5.4 169/462] mm: only enforce minimum stack gap size if its sensible Date: Wed, 6 Nov 2024 13:01:02 +0100 Message-ID: <20241106120335.693202176@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241106120331.497003148@linuxfoundation.org> References: <20241106120331.497003148@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-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 @@ -407,7 +407,7 @@ 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;