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 7021B328B47 for ; Tue, 3 Feb 2026 12:06:59 +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=1770120419; cv=none; b=j/1tRuA4RdYBF++sUBEomli/fLcjKSWfxl514tfiW/q/4k1Je4EfIqEuvbZt8XcEK7IUSe24OEpX9cTOpd1ojIvQiBNg6QpiIgJwiq9BZCfWjFK2BiJ7CabCVhYB5MuCxoJmgpcZXiGk1ob9msWeiCdMjBM7GNfM9l7DRm+eV6Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770120419; c=relaxed/simple; bh=0KcLqc+N8zEjVP0HspAs/kJO8xO1BQR2PuiOWro72KE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Cj1R2AQLwfW1g8ovfBYQNB9Z52c6UEBm9Q+BptGu5yxbwnCwVNbO8N48PeIjovmAKewnXXHYZrEFmwm14B7f1/d4xderTmqdNedqPyYHae4ChrTQ5PSUEs0VSZGubFyNHNJgW4gRDjhjrGkmQwU/Uyak5KuCO4fGbJ7UVFYTeks= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XrJd0z/7; 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="XrJd0z/7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1C53C116D0; Tue, 3 Feb 2026 12:06:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770120419; bh=0KcLqc+N8zEjVP0HspAs/kJO8xO1BQR2PuiOWro72KE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XrJd0z/7FpB56XCWMENM9mVUUvE/U6tYjmSw8Ot2g0vuHzm/A+jjcSF+ABqsMVKO4 Ug1ueMtfNEEZJcUGN6G5xSWJk5UmzjmeEygY3oiCTpoRFH8qK+EaiVKKCZe+yZpgHv 6XYimwbuf8WanI/BoupIey6jLtmcKlDQ3BL/S0s/nEeE8/bq0Eg7YIUc8VFwuaRftA 5LRKRfTdTSi+QpJvRTdmcpPvVo2coAjki7w0NwcxG5qqD9qHt7fqRo00Ssi2LLQjSi hxZK3I60lUcWubycIecFgkLWrlWJhPy/gJm7n3lK3/8CEwqVbqeANl0uRk0itBrHPx INnKv5ur6ZmPg== Date: Tue, 3 Feb 2026 17:36:52 +0530 From: Sumit Garg To: Sven =?iso-8859-1?Q?P=FCschel?= Cc: Marco Felsch , linux-kernel@vger.kernel.org, Matthew Wilcox , op-tee@lists.trustedfirmware.org, kernel@pengutronix.de, akpm@linux-foundation.org, Jens Wiklander , vbabka@suse.cz Subject: Re: [PATCH v2] tee: shm: fix slab page refcounting Message-ID: References: <20250325200740.3645331-1-m.felsch@pengutronix.de> <20250326110718.qzbwpmaf6xlcb4xf@pengutronix.de> <20250821174124.b6pco3izkns4qt2r@pengutronix.de> <20250822101522.wlwmdal5f4sqydjq@pengutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@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: Hi Sven, On Tue, Feb 03, 2026 at 12:55:08PM +0100, Sven Püschel wrote: > Hi, > > On 8/22/25 12:15 PM, Marco Felsch wrote: > > On 25-08-22, Sumit Garg wrote: > > > On Thu, Aug 21, 2025 at 07:41:24PM +0200, Marco Felsch wrote: > > > > Hi all, > > > > > > > > is this issue fixed with 6.17? I ran: > > > > > > > > git log v6.14...v6.17-rc1 drivers/tee/tee_shm.c > > > > > > > > and saw no changes. > > > Care to send a proper patch regarding what Matthew proposed in this > > > thread? > > I'm still not sure if the IOVs can be backed by other allocators too > > because the OP-TEE API allows arbitrary sizes. Therefore my hope was > > that one of the OP-TEE maintainers is taking care of this problem. > > > > I also wonder why no one spotted/reported this issue too. > > Any updates on how to proceed on this? I've ran into the issue today with > the latest kernel master when loading a sealed key blob using keyctl on a > Radxa Rock5T (rk3588): Can you check if fix suggested by Matthew here [1] fixes problem for you? If it does then can you create a proper fix patch for upstream around that? [1] https://lore.kernel.org/all/Z-Pc6C1YUqLyej3Z@casper.infradead.org/ -Sumit > > [   29.222792] ------------[ cut here ]------------ > [   29.223213] WARNING: include/linux/mm.h:1584 at > register_shm_helper+0x2b4/0x2d0, CPU#2: keyctl/262 > [   29.224005] Modules linked in: hantro_vpu v4l2_jpeg v4l2_vp9 > synopsys_hdmirx panthor v4l2_h264 drm_gpuvm drm_exec fuse > [   29.224965] CPU: 2 UID: 0 PID: 262 Comm: keyctl Not tainted > 6.19.0-rc8-00006-g6bd9ed02871f #2 PREEMPT > [   29.225777] Hardware name: Radxa ROCK 5T (DT) > [   29.226160] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS > BTYPE=--) > [   29.226769] pc : register_shm_helper+0x2b4/0x2d0 > [   29.227175] lr : register_shm_helper+0x178/0x2d0 > [   29.227581] sp : ffffffc0846aba70 > [   29.227872] x29: ffffffc0846aba90 x28: ffffff8107e7d600 x27: > 0000000000000000 > [   29.228502] x26: 0000000000000000 x25: ffffff810449e41a x24: > 0000000000000001 > [   29.229130] x23: ffffffc0846abaf0 x22: ffffffffffffffea x21: > ffffff8100cf2400 > [   29.229758] x20: ffffff81014ec960 x19: ffffff81023da100 x18: > 0000000085a8c61a > [   29.230387] x17: 000000000836c99b x16: 0000000018aab74d x15: > 6436303939393264 > [   29.231016] x14: 6631323431303432 x13: 6466313234313034 x12: > 3262373862366634 > [   29.231643] x11: 3166653364353337 x10: ffffffc086adc2f8 x9 : > ffffffc0805dde38 > [   29.232272] x8 : ffffff8100c10018 x7 : 0000000000000001 x6 : > 0000000000000000 > [   29.232900] x5 : ffffff8100c10010 x4 : ffffff810449e000 x3 : > fffffffec4112600 > [   29.233528] x2 : 00000000000000f5 x1 : fffffffec4112600 x0 : > 0000000000000281 > [   29.234157] Call trace: > [   29.234374]  register_shm_helper+0x2b4/0x2d0 (P) > [   29.234782]  tee_shm_register_kernel_buf+0x68/0xa0 > [   29.235205]  trusted_tee_unseal+0x5c/0x150 > [   29.235570]  trusted_instantiate+0x114/0x1f0 > [   29.235948]  __key_instantiate_and_link+0x60/0x1c0 > [   29.236369]  __key_create_or_update+0x2b8/0x458 > [   29.236769]  key_create_or_update+0x18/0x28 > [   29.237138]  __arm64_sys_add_key+0x138/0x230 > [   29.237515]  do_el0_svc+0x70/0x100 > [   29.237819]  el0_svc+0x30/0xf8 > [   29.238092]  el0t_64_sync_handler+0x98/0xe0 > [   29.238462]  el0t_64_sync+0x154/0x158 > [   29.238787] ---[ end trace 0000000000000000 ]--- > > > Sincerely >     Sven > > > > > > Regards, > > Marco > > > > > > > -Sumit > > > > > > > Regards, > > > > Marco > > > > > > > > On 25-04-28, Jens Wiklander wrote: > > > > > On Thu, Mar 27, 2025 at 5:42 AM Sumit Garg wrote: > > > > > > On Wed, Mar 26, 2025 at 02:47:46PM +0100, Jens Wiklander wrote: > > > > > > > On Wed, Mar 26, 2025 at 12:07 PM Marco Felsch wrote: > > > > > > > > On 25-03-26, Matthew Wilcox wrote: > > > > > > > > > On Tue, Mar 25, 2025 at 09:07:39PM +0100, Marco Felsch wrote: > > > > > > > > > > Skip manipulating the refcount in case of slab pages according commit > > > > > > > > > > b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page"). > > > > > > > > > This almost certainly isn't right. I know nothing about TEE, but that > > > > > > > > > you are doing this indicates a problem. The hack that we put into > > > > > > > > > networking should not be blindly replicated. > > > > > > > > > > > > > > > > > > Why are you taking a reference on the pages to begin with? Is it copy > > > > > > > > > and pasted from somewhere else, or was there actual thought put into it? > > > > > > > > Not sure, this belongs to the TEE maintainers. > > > > > > > I don't know. We were getting the user pages first, so I assume we > > > > > > > just did the same thing when we added support for kernel pages. > > > > > > > > > > > > > > > > If it's "prevent the caller from freeing the allocation", well, it never > > > > > > > > > accomplished that with slab allocations. So for callers that do kmalloc > > > > > > > > > (eg setup_mm_hdr() in drivers/firmware/efi/stmm/tee_stmm_efi.c), you > > > > > > > > > have to rely on them not freeing the allocation while the TEE driver > > > > > > > > > has it. > > > > > > It's not just about the TEE driver but rather if the TEE implementation > > > > > > (a trusted OS) to whom the page is registered with. We don't want the > > > > > > trusted OS to work on registered kernel pages if they gets free somehow > > > > > > in the TEE client driver. Having a reference in the TEE subsystem > > > > > > assured us that won't happen. But if you say slab allocations are still > > > > > > prone the kernel pages getting freed even after refcount then can you > > > > > > suggest how should we handle this better? > > > > > > > > > > > > As otherwise it can cause very hard to debug problems if trusted OS can > > > > > > manipulate kernel pages that are no longer available. > > > > > We must be able to rely on the kernel callers to have the needed > > > > > references before calling tee_shm_register_kernel_buf() and to keep > > > > > those until after calling tee_shm_free(). > > > > > > > > > > > > > > > > > > > And if that's your API contract, then there's no point in taking > > > > > > > > > refcounts on other kinds of pages either; it's just unnecessary atomic > > > > > > > > > instructions. So the right patch might be something like this: > > > > > > > > > > > > > > > > > > +++ b/drivers/tee/tee_shm.c > > > > > > > > > @@ -15,29 +15,11 @@ > > > > > > > > > #include > > > > > > > > > #include "tee_private.h" > > > > > > > > I had the same diff but didn't went this way since we can't be sure that > > > > > > > > iov's are always slab backed. As far as I understood IOVs. In > > > > > > > > 'worst-case' scenario an iov can be backed by different page types too. > > > > > > > We're only using kvec's. Briefly, before commit 7bdee4157591 ("tee: > > > > > > > Use iov_iter to better support shared buffer registration") we checked > > > > > > > with is_vmalloc_addr() || is_kmap_addr(). I like Matthew's suggestion, > > > > > > > it's nice to fix problems by deleting code. :-) > > > > > > > > > > > > > > Sumit, you know the callers better. What do you think? > > > > > > If we don't have a sane way to refcont registered kernel pages in TEE > > > > > > subsystem then yeah we have to solely rely on the client drivers to > > > > > > behave properly. Nevertheless, it's still within the kernel boundaries > > > > > > which we can rely upon. > > > > > Yes. > > > > > > > > > > Cheers, > > > > > Jens > >