From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 54E91237180; Tue, 11 Aug 2026 03:52:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786420373; cv=none; b=V5jSJxE14RC19DCjvqE409pMvldjzTCA4aPB2l5xN1DV3AOtJJ7WIi4AQPBVzyisuJVgxjPW8b3sPcWSo6FHqlr34YCY1lQTZWJpzo0/x5ku6ZL0COQNSD6pT7oZ5A9vHbyxc2prjHj2hXRUP1ly2tul5qIBkky3RjgiVQBuKNk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786420373; c=relaxed/simple; bh=SIcrw8jz2TL5YSgaZdCMeOaKYAkUvmKaAujnQyj/r0Q=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=nLqXgMnmCpLm+rGkTlbIP5iVmdsONrRNKjoELwU1yHLVADIpREioIuA530ibZqfl/zXcUfRjCAQYM1IKt4CDADXlY6MyknKo7SZNwCXFFtN4MaLgnHk7+SWR2Ag9cHaELPi9/TZ7URgA2WLxJlm/XfFZaq0V+72shn06csOu5OA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=DaEru8YP; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="DaEru8YP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 900151F000E9; Tue, 11 Aug 2026 03:52:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1786420371; bh=tQ8MTXU7PXH/k046gdgNu+2KYPZDiwOczpAepdH9QcY=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=DaEru8YPOYGZZ6RTXqtSimMxPDe90BY2dH0YrIJI1Y6AP6qOdJn23xuERg9ByK+n0 jj/KDEDzHxxC69nBa8lwtpHndN0ygmu1lIdEuA2mtnKgm1pRfGsnHE5UpLPdlEgILn bN+aN/0bFsp8KhGmm08kgcSaiq+B8P2IqQcE0eZQ= Date: Mon, 10 Aug 2026 20:52:51 -0700 From: Andrew Morton To: Hao Ge Cc: Suren Baghdasaryan , Luis Chamberlain , Petr Pavlu , Daniel Gomez , Sami Tolvanen , Aaron Tomlin , linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v4 0/2] alloc_tag: fix undetected compressed tag overflow when profiling is disabled Message-Id: <20260810205251.3fce0ec86ee20925fd577c26@linux-foundation.org> In-Reply-To: <20260810093955.153015-1-hao.ge@linux.dev> References: <20260810093955.153015-1-hao.ge@linux.dev> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 10 Aug 2026 17:39:53 +0800 Hao Ge wrote: > v3 was a single patch. After discussion with Suren and Andrew we went > for a more graceful approach: rather than failing the module load on > overflow, let it load without profiling. Once profiling is disabled, > codetag_needs_module_section() returns false, so on retry the codetag > section is placed as regular module data. > > A new patch (1/2) is added to move release_module_tags() above > reserve_module_tags(), since the overflow path now has to call it and > the helper sits below it. Thing is, [2/2] has cc:stable but it requires [1/2] to be able to be compiled. [1/2] doesn't have cc:stable so we're asking -stable folks to backport a patch which doesn't compile. Resolve this by using the same Fixes: and cc:stable in both patches. > release_module_tags() is what module unload calls to drop a module's > reservation from the maple tree. By the time reserve_module_tags() > detects the overflow it has already stored that reservation, and the > -EAGAIN return skips vm_module_tags_populate(), so the backing pages > never get mapped. If reserve_module_tags() returns without calling > release_module_tags(), the stale entry keeps pointing at that unmapped > range; when the module is later unloaded, release_module_tags() walks > it and panics. AI review had a lot to say about this patchset. Some pre-existing, some not: https://sashiko.dev/#/patchset/20260810093955.153015-1-hao.ge@linux.dev offtopic: alloc_tag isn't getting allmodconfig build coverage at this time because: 1: MEM_ALLOC_PROFILING depends on !DEBUG_FORCE_WEAK_PER_CPU (why? I can't figure that out) 2: x86_64 allmodconfig enables DEBUG_FORCE_WEAK_PER_CPU, despite it being for s390 and alpha. In fact it might be alpha-only. Adding depends on ALPHA || S390 in there fixes this.