From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-162.mta1.migadu.com (out-162.mta1.migadu.com [95.215.58.162]) (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 5BBBA364038 for ; Tue, 4 Aug 2026 12:21:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.162 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785846067; cv=none; b=LpB/y+QYDEjFz4hNIw+iadGrK7GiuIR+Rd339Io6iWvJ5I+d6Mwg8MzHnKBOUXM0FEFp/gE6fr4R90iNothCkJzRnAQvwop7q4K9fiDjU+SQdK8jRhF6gNpeg3hzmN5UwbydZaV4QddKzSlIjgdenASA/OBgkunAkxGbxZzZG9g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785846067; c=relaxed/simple; bh=F7FMyRvxWAF2Z7610HOVSsKGPQbXiYODSlxaQVk9MMg=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=AlIeIqGq4Vs+jW8eYfzbfsqvbYGpXOrWaukgRDQdaoNaJlrkJYhNHK4pHA5kW3p5hUeZXn2T5kmyh+fhXUNPFIMiNlWVBrj/6BccrsIGG8VP00WB99d5YlQxIUFmOAUP0xh8mGlKdIqmDqoH+toNMBtOdavuygS1URDHZmhplYE= 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=TGkVHhF8; arc=none smtp.client-ip=95.215.58.162 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="TGkVHhF8" 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=1785846062; 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=2sUfUtBlTrxznqbjUXb2OOf/gmZXR4ctuPKgvPoVXf0=; b=TGkVHhF8YYdSRTNBqyi/ZBaxf+Ijgcmu0ex0JOCEKNtRbQn+dIAwivlGIyX6KFGkvqeAnR AjHauDvs3Kzm/TUa6pi/7E79wDikBv1tyzMwlLRjkOrWQelV0rajHHggD2M7ky2Xr6UJHL M4lVUITZibvR6Zmv5tlYC8B7oCq/rXM= 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 v2] alloc_tag: fix undetected compressed tag overflow when profiling is disabled Date: Tue, 4 Aug 2026 20:20:38 +0800 Message-Id: <20260804122038.190270-1-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. Remove the mem_alloc_profiling_enabled() guard. Also return an error after shutdown_mem_profiling() to skip vm_module_tags_populate(), as the mapped pages would never be reused - shutdown_mem_profiling() sets mem_profiling_support to false, so no future module load enters the codetag path. Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression") Cc: stable@vger.kernel.org Signed-off-by: Hao Ge --- Changes in v2: - Return error after shutdown_mem_profiling() to skip unnecessary vm_module_tags_populate() v1 link: https://lore.kernel.org/all/20260804064408.105033-1-hao.ge@linux.dev/ --- mm/alloc_tag.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c index 52aece27b00e..d8c36430f1c0 100644 --- a/mm/alloc_tag.c +++ b/mm/alloc_tag.c @@ -904,10 +904,11 @@ 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); + return ERR_PTR(-ENOSPC); } grow_res = vm_module_tags_populate(); -- 2.25.1