From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 4BE2741A547 for ; Tue, 4 Aug 2026 06:44:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785825874; cv=none; b=BRnpCASvCV8VN6Boci8y+IqOMr4AvyP8eh2YonhARCXx6kQ3qhMsPpm6oukoxBgYGGRoav7FY3E60ZE7n5zM7RrtQjqMEoxO3TOpREKm69jxBrvwCAp7QwPfaqyUPKlKQHUKqc1qmjxmdC8KHfkZu7I6c+Qr64PyZMxCXrF1+TY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785825874; c=relaxed/simple; bh=auyo8K/F0LOd5Qt/4SOXsPr0pHJn1K42mGK0XoMRGS4=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=sR7WTZS/fQ0dBYin+soogLFU8LbPcNwQL3kJbs4CLqCptDyMNYkXrnyCZtLoDENT/xV9uljSLZz2CpTGIw298TG6+F3wiz8VjEF6NBHy9a5Cy5O5LR85jeMmC8oohiCGdSMpOOn4PQvZfQjrvsUnZnofz20o8E6LgJG+62/tTqU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Ta9rkB+P; arc=none smtp.client-ip=91.218.175.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Ta9rkB+P" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1785825870; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=zKx75AMauM0RaOxCF4agyTe8wC94OE6OVaWCflojIjw=; b=Ta9rkB+PXIYAYLAnSW3VYj9gennu9yzIK27t64FtepCEz+k78xTO29O9dhgq+0Ezcyw1qk TEPtyLHvsPGcg+yWOfldKG1o7yf23+dGfP96HgFAOrMhHuxekJqF/hJyjm38xpOl7f+1Sx O6pgGIgtEiRTc7DdzWXX7bq+BN/rk5Y= From: Hao Ge To: Suren Baghdasaryan , Andrew Morton , Hao Ge Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Abhishek Bapat , stable@vger.kernel.org Subject: [PATCH] alloc_tag: fix undetected compressed tag overflow when profiling is disabled Date: Tue, 4 Aug 2026 14:44:08 +0800 Message-Id: <20260804064408.105033-1-hao.ge@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT In reserve_module_tags(), the tag overflow check is gated on mem_alloc_profiling_enabled(): if (mem_alloc_profiling_enabled() && !tags_addressable()) If profiling is toggled off at runtime and a module is loaded whose tags exceed the compressed-mode limit, shutdown_mem_profiling() is skipped. vm_module_tags_populate() still maps memory for the tags and the module loads successfully, but the total tag count now exceeds what NR_UNUSED_PAGEFLAG_BITS can address. Once profiling is re-enabled, ref_to_idx() computes each tag's index as its position in the alloc_tag array. update_page_tag_ref() masks it to alloc_tag_ref_mask before storing in page->flags. Indices beyond the mask are truncated and idx_to_ref() resolves them to wrong tags. mem_alloc_profiling_enabled() and mem_profiling_compressed are independent. Once compressed mode is established at boot, it stays active regardless of runtime toggles of mem_profiling. We therefore remove the mem_alloc_profiling_enabled() guard. Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression") Cc: stable@vger.kernel.org Signed-off-by: Hao Ge --- mm/alloc_tag.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c index 52aece27b00e..a387a17211de 100644 --- a/mm/alloc_tag.c +++ b/mm/alloc_tag.c @@ -904,7 +904,7 @@ static void *reserve_module_tags(struct module *mod, unsigned long size, int grow_res; module_tags.size = offset + size; - if (mem_alloc_profiling_enabled() && !tags_addressable()) { + if (!tags_addressable()) { shutdown_mem_profiling(true); pr_warn("With module %s there are too many tags to fit in %d page flag bits. Memory allocation profiling is disabled!\n", mod->name, NR_UNUSED_PAGEFLAG_BITS); -- 2.25.1