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 3BAC0194C62; Thu, 18 Apr 2024 19:45:48 +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=1713469549; cv=none; b=VqvR9C6I9hX5kFd3KznBHJpCoHWSkhjfX/p0NTjiqQxRxch5R/y7FGZMZDZRAEQIcGIaHUUDi+0L1QDLUqOL2BGSWH3O8Ak2R6gQeN0pzaC1HVhiNjFAz1qEL4obMskQnCcUbiIk7/6UFt7FWU05EUzhLs5chKh1VKa3lNOhL5M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713469549; c=relaxed/simple; bh=dHO0bamdxUUeACG8WtZho+GCcL4yBYsb4entMWbbmyQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NeuLydmOy43wm77BprVIRDo9C2R0ZLK1SeQ9zN3+wz0EaAEPlphAvRSyd7M3fb9/ySjonJ1hgZhbmmAO20tH97yReu37Wzf8qSkWXdQIWo/9BPVN481ZQNKdSlBdpj+h7YQ8DVBTKArq/x62lwd6T0IHYsCNuhRNzCIdtEFEEf8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CmVx6dRz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CmVx6dRz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E87BEC113CC; Thu, 18 Apr 2024 19:45:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713469548; bh=dHO0bamdxUUeACG8WtZho+GCcL4yBYsb4entMWbbmyQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CmVx6dRzicEYeby+eqehWh43quHdNoBbYY/i36pebwlC3hu3ZmeS4VjBXURj7aNy3 iceEu2pMqBEVdzfyoNs6zYPwdeFEVjMU4daLSOF+34RPv/VgtKgm1TQzPbhCvKJCzp PwHKW3yddAFwEE2clGQPe9VCz0EWlv35PYz4PkEEkLTMMrd+GAZOMmGABmKaUl5Y8d 4udjlt3Z97dUrMWxxJyIATuY3MTqmnZM5WdZYeq2ykeLqUHwwS1ZlLE9RAdOJI4t5m dZHSPXrDPE8q2nmOH9o+Xw5o1ED5ivvKuuyvGRHdoAhgoYmdvYsWWSvRA9smcyAVNW 9J1gVzjdVbV+Q== Date: Thu, 18 Apr 2024 22:44:31 +0300 From: Mike Rapoport To: Nadav Amit Cc: Linux Kernel Mailing List , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Catalin Marinas , Christoph Hellwig , Helge Deller , Lorenzo Stoakes , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , Mathieu Desnoyers , Michael Ellerman , Palmer Dabbelt , Peter Zijlstra , Russell King , Song Liu , Steven Rostedt , Thomas Gleixner , Uladzislau Rezki , Will Deacon , bpf , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "open list:MEMORY MANAGEMENT" , linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev , the arch/x86 maintainers Subject: Re: [RFC PATCH 3/7] module: [ Message-ID: References: <20240411160526.2093408-1-rppt@kernel.org> <20240411160526.2093408-4-rppt@kernel.org> <0C4B9C1A-97DE-4798-8256-158369AF42A4@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Apr 18, 2024 at 10:31:16PM +0300, Nadav Amit wrote: > > > On 18 Apr 2024, at 13:20, Mike Rapoport wrote: > > > > On Tue, Apr 16, 2024 at 12:36:08PM +0300, Nadav Amit wrote: > >> > >> > >> > >> I might be missing something, but it seems a bit racy. > >> > >> IIUC, module_finalize() calls alternatives_smp_module_add(). At this > >> point, since you don’t hold the text_mutex, some might do text_poke(), > >> e.g., by enabling/disabling static-key, and the update would be > >> overwritten. No? > > > > Right :( > > Even worse, for UP case alternatives_smp_unlock() will "patch" still empty > > area. > > > > So I'm thinking about calling alternatives_smp_module_add() from an > > additional callback after the execmem_update_copy(). > > > > Does it make sense to you? > > Going over the code again - I might have just been wrong: I confused the > alternatives and the jump-label mechanisms (as they do share a lot of > code and characteristics). > > The jump-labels are updated when prepare_coming_module() is called, which > happens after post_relocation() [which means they would be updated using > text_poke() “inefficiently” but should be safe]. > > The “alternatives” appear only to use text_poke() (in contrast for > text_poke_early()) from very specific few flows, e.g., > common_cpu_up() -> alternatives_enable_smp(). > > Are those flows pose a problem after boot? Yes, common_cpu_up is called on CPU hotplug, so it's possible to have a race between alternatives_smp_module_add() and common_cpu_up() -> alternatives_enable_smp(). And in UP case alternatives_smp_module_add() will call alternatives_smp_unlock() that will patch module text before it is updated. > Anyhow, sorry for the noise. On the contrary, I would have missed it. -- Sincerely yours, Mike. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9B558C4345F for ; Thu, 18 Apr 2024 19:45:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=BjwbZ+jWZtBiL8rV8MHMw9Jk6b0uyZaCOie+b4GUb0k=; b=ZBHQVARuC2S4ye WYKsu/YBnE8+qIcQxAWHzVZEXh7VstzQxX80Eo5Vj2vnJ8VWhBdQ37Pls+INFsl3nKxdEmoZK6uK1 Bs6xq5DKM5wjOw4W4K4ZFEQY0jJs9Y2Fdgb618Ar7n2tLgGLgRZ2ae0uyDz/lpp5uTZ06BFjX+1lK imwdkMxsj418uhG66yRwzCYKlZuBRvmqrO/lVWbqDiUfPrSVoFGmRpp3RgC9I74o0MZyFkctvHS0Z oAndEpsDz110KLV5/yIPcC1gh62Kl0PGn802yOKKO37wmrYzBJOrWqSZf82fTgUGeQsukTPoU/ij5 ehMqvG+n2/PGyk2xYfAg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rxXhh-00000003VVU-3IBQ; Thu, 18 Apr 2024 19:45:53 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rxXhe-00000003VS4-0RfC; Thu, 18 Apr 2024 19:45:52 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id EB01D618E2; Thu, 18 Apr 2024 19:45:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E87BEC113CC; Thu, 18 Apr 2024 19:45:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713469548; bh=dHO0bamdxUUeACG8WtZho+GCcL4yBYsb4entMWbbmyQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CmVx6dRzicEYeby+eqehWh43quHdNoBbYY/i36pebwlC3hu3ZmeS4VjBXURj7aNy3 iceEu2pMqBEVdzfyoNs6zYPwdeFEVjMU4daLSOF+34RPv/VgtKgm1TQzPbhCvKJCzp PwHKW3yddAFwEE2clGQPe9VCz0EWlv35PYz4PkEEkLTMMrd+GAZOMmGABmKaUl5Y8d 4udjlt3Z97dUrMWxxJyIATuY3MTqmnZM5WdZYeq2ykeLqUHwwS1ZlLE9RAdOJI4t5m dZHSPXrDPE8q2nmOH9o+Xw5o1ED5ivvKuuyvGRHdoAhgoYmdvYsWWSvRA9smcyAVNW 9J1gVzjdVbV+Q== Date: Thu, 18 Apr 2024 22:44:31 +0300 From: Mike Rapoport To: Nadav Amit Cc: Linux Kernel Mailing List , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Catalin Marinas , Christoph Hellwig , Helge Deller , Lorenzo Stoakes , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , Mathieu Desnoyers , Michael Ellerman , Palmer Dabbelt , Peter Zijlstra , Russell King , Song Liu , Steven Rostedt , Thomas Gleixner , Uladzislau Rezki , Will Deacon , bpf , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "open list:MEMORY MANAGEMENT" , linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev , the arch/x86 maintainers Subject: Re: [RFC PATCH 3/7] module: [ Message-ID: References: <20240411160526.2093408-1-rppt@kernel.org> <20240411160526.2093408-4-rppt@kernel.org> <0C4B9C1A-97DE-4798-8256-158369AF42A4@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240418_124550_303089_C5F455AF X-CRM114-Status: GOOD ( 23.67 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; 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Fri, 19 Apr 2024 05:45:51 +1000 (AEST) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id EB01D618E2; Thu, 18 Apr 2024 19:45:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E87BEC113CC; Thu, 18 Apr 2024 19:45:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713469548; bh=dHO0bamdxUUeACG8WtZho+GCcL4yBYsb4entMWbbmyQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CmVx6dRzicEYeby+eqehWh43quHdNoBbYY/i36pebwlC3hu3ZmeS4VjBXURj7aNy3 iceEu2pMqBEVdzfyoNs6zYPwdeFEVjMU4daLSOF+34RPv/VgtKgm1TQzPbhCvKJCzp PwHKW3yddAFwEE2clGQPe9VCz0EWlv35PYz4PkEEkLTMMrd+GAZOMmGABmKaUl5Y8d 4udjlt3Z97dUrMWxxJyIATuY3MTqmnZM5WdZYeq2ykeLqUHwwS1ZlLE9RAdOJI4t5m dZHSPXrDPE8q2nmOH9o+Xw5o1ED5ivvKuuyvGRHdoAhgoYmdvYsWWSvRA9smcyAVNW 9J1gVzjdVbV+Q== Date: Thu, 18 Apr 2024 22:44:31 +0300 From: Mike Rapoport To: Nadav Amit Subject: Re: [RFC PATCH 3/7] module: [ Message-ID: References: <20240411160526.2093408-1-rppt@kernel.org> <20240411160526.2093408-4-rppt@kernel.org> <0C4B9C1A-97DE-4798-8256-158369AF42A4@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Peter Zijlstra , Catalin Marinas , Song Liu , linux-riscv@lists.infradead.org, Will Deacon , linux-arch@vger.kernel.org, Helge Deller , the arch/x86 maintainers , Russell King , Christoph Hellwig , linux-trace-kernel@vger.kernel.org, Arnd Bergmann , Steven Rostedt , Mathieu Desnoyers , Andy Lutomirski , Thomas Gleixner , Andrew Morton , linux-arm-kernel@lists.infradead.org, Lorenzo Stoakes , linux-parisc@vger.kernel.org, "open list:MEMORY MANAGEMENT" , Linux Kernel Mailing List , Luis Chamberlain , Uladzislau Rezki , Palmer Dabbelt , Masa mi Hiramatsu , bpf , linuxppc-dev , linux-modules@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Apr 18, 2024 at 10:31:16PM +0300, Nadav Amit wrote: > > > On 18 Apr 2024, at 13:20, Mike Rapoport wrote: > > > > On Tue, Apr 16, 2024 at 12:36:08PM +0300, Nadav Amit wrote: > >> > >> > >> > >> I might be missing something, but it seems a bit racy. > >> > >> IIUC, module_finalize() calls alternatives_smp_module_add(). At this > >> point, since you don’t hold the text_mutex, some might do text_poke(), > >> e.g., by enabling/disabling static-key, and the update would be > >> overwritten. No? > > > > Right :( > > Even worse, for UP case alternatives_smp_unlock() will "patch" still empty > > area. > > > > So I'm thinking about calling alternatives_smp_module_add() from an > > additional callback after the execmem_update_copy(). > > > > Does it make sense to you? > > Going over the code again - I might have just been wrong: I confused the > alternatives and the jump-label mechanisms (as they do share a lot of > code and characteristics). > > The jump-labels are updated when prepare_coming_module() is called, which > happens after post_relocation() [which means they would be updated using > text_poke() “inefficiently” but should be safe]. > > The “alternatives” appear only to use text_poke() (in contrast for > text_poke_early()) from very specific few flows, e.g., > common_cpu_up() -> alternatives_enable_smp(). > > Are those flows pose a problem after boot? Yes, common_cpu_up is called on CPU hotplug, so it's possible to have a race between alternatives_smp_module_add() and common_cpu_up() -> alternatives_enable_smp(). And in UP case alternatives_smp_module_add() will call alternatives_smp_unlock() that will patch module text before it is updated. > Anyhow, sorry for the noise. On the contrary, I would have missed it. -- Sincerely yours, Mike. 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charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gVGh1LCBBcHIgMTgsIDIwMjQgYXQgMTA6MzE6MTZQTSArMDMwMCwgTmFkYXYgQW1pdCB3cm90 ZToKPiAKPiA+IE9uIDE4IEFwciAyMDI0LCBhdCAxMzoyMCwgTWlrZSBSYXBvcG9ydCA8cnBwdEBr ZXJuZWwub3JnPiB3cm90ZToKPiA+IAo+ID4gT24gVHVlLCBBcHIgMTYsIDIwMjQgYXQgMTI6MzY6 MDhQTSArMDMwMCwgTmFkYXYgQW1pdCB3cm90ZToKPiA+PiAKPiA+PiAKPiA+PiAKPiA+PiBJIG1p Z2h0IGJlIG1pc3Npbmcgc29tZXRoaW5nLCBidXQgaXQgc2VlbXMgYSBiaXQgcmFjeS4KPiA+PiAK PiA+PiBJSVVDLCBtb2R1bGVfZmluYWxpemUoKSBjYWxscyBhbHRlcm5hdGl2ZXNfc21wX21vZHVs ZV9hZGQoKS4gQXQgdGhpcwo+ID4+IHBvaW50LCBzaW5jZSB5b3UgZG9u4oCZdCBob2xkIHRoZSB0 ZXh0X211dGV4LCBzb21lIG1pZ2h0IGRvIHRleHRfcG9rZSgpLAo+ID4+IGUuZy4sIGJ5IGVuYWJs aW5nL2Rpc2FibGluZyBzdGF0aWMta2V5LCBhbmQgdGhlIHVwZGF0ZSB3b3VsZCBiZQo+ID4+IG92 ZXJ3cml0dGVuLiBObz8KPiA+IAo+ID4gUmlnaHQgOigKPiA+IEV2ZW4gd29yc2UsIGZvciBVUCBj YXNlIGFsdGVybmF0aXZlc19zbXBfdW5sb2NrKCkgd2lsbCAicGF0Y2giIHN0aWxsIGVtcHR5Cj4g PiBhcmVhLgo+ID4gCj4gPiBTbyBJJ20gdGhpbmtpbmcgYWJvdXQgY2FsbGluZyBhbHRlcm5hdGl2 ZXNfc21wX21vZHVsZV9hZGQoKSBmcm9tIGFuCj4gPiBhZGRpdGlvbmFsIGNhbGxiYWNrIGFmdGVy IHRoZSBleGVjbWVtX3VwZGF0ZV9jb3B5KCkuCj4gPiAKPiA+IERvZXMgaXQgbWFrZSBzZW5zZSB0 byB5b3U/Cj4gCj4gR29pbmcgb3ZlciB0aGUgY29kZSBhZ2FpbiAtIEkgbWlnaHQgaGF2ZSBqdXN0 IGJlZW4gd3Jvbmc6IEkgY29uZnVzZWQgdGhlCj4gYWx0ZXJuYXRpdmVzIGFuZCB0aGUganVtcC1s YWJlbCBtZWNoYW5pc21zIChhcyB0aGV5IGRvIHNoYXJlIGEgbG90IG9mCj4gY29kZSBhbmQgY2hh cmFjdGVyaXN0aWNzKS4KPiAKPiBUaGUganVtcC1sYWJlbHMgYXJlIHVwZGF0ZWQgd2hlbiBwcmVw YXJlX2NvbWluZ19tb2R1bGUoKSBpcyBjYWxsZWQsIHdoaWNoCj4gaGFwcGVucyBhZnRlciBwb3N0 X3JlbG9jYXRpb24oKSBbd2hpY2ggbWVhbnMgdGhleSB3b3VsZCBiZSB1cGRhdGVkIHVzaW5nCj4g dGV4dF9wb2tlKCkg4oCcaW5lZmZpY2llbnRseeKAnSBidXQgc2hvdWxkIGJlIHNhZmVdLgo+IAo+ IFRoZSDigJxhbHRlcm5hdGl2ZXPigJ0gYXBwZWFyIG9ubHkgdG8gdXNlIHRleHRfcG9rZSgpIChp biBjb250cmFzdCBmb3IKPiB0ZXh0X3Bva2VfZWFybHkoKSkgZnJvbSB2ZXJ5IHNwZWNpZmljIGZl dyBmbG93cywgZS5nLiwgCj4gY29tbW9uX2NwdV91cCgpIC0+IGFsdGVybmF0aXZlc19lbmFibGVf c21wKCkuCj4gCj4gQXJlIHRob3NlIGZsb3dzIHBvc2UgYSBwcm9ibGVtIGFmdGVyIGJvb3Q/CgpZ ZXMsIGNvbW1vbl9jcHVfdXAgaXMgY2FsbGVkICBvbiBDUFUgaG90cGx1Zywgc28gaXQncyBwb3Nz aWJsZSB0byBoYXZlIGEKcmFjZSBiZXR3ZWVuIGFsdGVybmF0aXZlc19zbXBfbW9kdWxlX2FkZCgp IGFuZCBjb21tb25fY3B1X3VwKCkgLT4KYWx0ZXJuYXRpdmVzX2VuYWJsZV9zbXAoKS4KCkFuZCBp biBVUCBjYXNlIGFsdGVybmF0aXZlc19zbXBfbW9kdWxlX2FkZCgpIHdpbGwgY2FsbAphbHRlcm5h dGl2ZXNfc21wX3VubG9jaygpIHRoYXQgd2lsbCBwYXRjaCBtb2R1bGUgdGV4dCBiZWZvcmUgaXQg aXMgdXBkYXRlZC4KCj4gQW55aG93LCBzb3JyeSBmb3IgdGhlIG5vaXNlLgoKT24gdGhlIGNvbnRy YXJ5LCBJIHdvdWxkIGhhdmUgbWlzc2VkIGl0LgoKLS0gClNpbmNlcmVseSB5b3VycywKTWlrZS4K Cl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCmxpbnV4LWFy bS1rZXJuZWwgbWFpbGluZyBsaXN0CmxpbnV4LWFybS1rZXJuZWxAbGlzdHMuaW5mcmFkZWFkLm9y ZwpodHRwOi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2xpbnV4LWFybS1r ZXJuZWwK