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 963B814D2B8; Tue, 23 Jul 2024 16:21:08 +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=1721751668; cv=none; b=AjAyV5CKchxUq4syeyWoHzMIMDm4mqNR/rFcIHNIC62iD96tWh+r6Ltmvys4rDH+s5DTGtfSHxis3CCslzty6hef5SvrIylzXIOrGJtZ4sF28UrQbb00ZmWWPtutE0xIAOW1WVsAy+juqqEJMlX6x6500FyZNThc+HOJ9TgPV+s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721751668; c=relaxed/simple; bh=ibgOg0b+WNf0hExtbAkMakcq3rUFIvmNPQsl79AMda8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ge+OD45wgokSSb8gsVt0v/hB36NFAFRo5v7h4kv2ueBH5GcKHFkbK2sSjIB7jxsLcPMOTiL3tZWsogNq0EuJoFXnVcKERWWblRNEXw5oygjPeefeILLTLn4jypAndfkOuwpJ1PiCOJyT/y+rnpuQuf0rhWQHTUQinOzWBK7wKLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Tm3Hr5Jk; 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="Tm3Hr5Jk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AB9FC4AF09; Tue, 23 Jul 2024 16:21:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1721751668; bh=ibgOg0b+WNf0hExtbAkMakcq3rUFIvmNPQsl79AMda8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Tm3Hr5JkaqbRrYxNoojwnOT5kyuBAFWFXzQlAQCRZrWYBohMm0dycCWPes48ewCAa ApXV+PGjWIuM+1COABF2TQ2E0ZGCDVs79yN3P4U7pmvUoyBdZiGVEz0RTPuEI5goyk XExPXRvm7yaOV1V0u5WPkPbtSGhyzY1LKh+Dat438yfCcmzdZfKADtS4cV/xUQicH2 05f3bxxuJ5LNew3lZY4r7DJNRlRxz6NxNFmij3megUTig30E9d7D8C5X4AG/yiq5aj o6Xz+hhMx2JT/CXeIYk08kY90WGFLeCTiagIak3I5HkgDQxMbYGBGU7TgwM+rdJMQu Wu/O3cPsm7JLQ== Date: Tue, 23 Jul 2024 10:21:07 -0600 From: Rob Herring To: Lizhi Hou Cc: Amit Machhiwal , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, Bjorn Helgaas , Saravana Kannan , Vaibhav Jain , Nicholas Piggin , Michael Ellerman , Vaidyanathan Srinivasan , Kowshik Jois B S , Lukas Wunner Subject: Re: [PATCH v2] PCI: Fix crash during pci_dev hot-unplug on pseries KVM guest Message-ID: <20240723162107.GA501469-robh@kernel.org> References: <20240715080726.2496198-1-amachhiw@linux.ibm.com> Precedence: bulk X-Mailing-List: devicetree@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 Mon, Jul 15, 2024 at 01:52:30PM -0700, Lizhi Hou wrote: > > On 7/15/24 11:55, Rob Herring wrote: > > On Mon, Jul 15, 2024 at 2:08 AM Amit Machhiwal wrote: > > > With CONFIG_PCI_DYNAMIC_OF_NODES [1], a hot-plug and hot-unplug sequence > > > of a PCI device attached to a PCI-bridge causes following kernel Oops on > > > a pseries KVM guest: > > > > > > RTAS: event: 2, Type: Hotplug Event (229), Severity: 1 > > > Kernel attempted to read user page (10ec00000048) - exploit attempt? (uid: 0) > > > BUG: Unable to handle kernel data access on read at 0x10ec00000048 > > > Faulting instruction address: 0xc0000000012d8728 > > > Oops: Kernel access of bad area, sig: 11 [#1] > > > LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries > > > > > > NIP [c0000000012d8728] __of_changeset_entry_invert+0x10/0x1ac > > > LR [c0000000012da7f0] __of_changeset_revert_entries+0x98/0x180 > > > Call Trace: > > > [c00000000bcc3970] [c0000000012daa60] of_changeset_revert+0x58/0xd8 > > > [c00000000bcc39c0] [c000000000d0ed78] of_pci_remove_node+0x74/0xb0 > > > [c00000000bcc39f0] [c000000000cdcfe0] pci_stop_bus_device+0xf4/0x138 > > > [c00000000bcc3a30] [c000000000cdd140] pci_stop_and_remove_bus_device_locked+0x34/0x64 > > > [c00000000bcc3a60] [c000000000cf3780] remove_store+0xf0/0x108 > > > [c00000000bcc3ab0] [c000000000e89e04] dev_attr_store+0x34/0x78 > > > [c00000000bcc3ad0] [c0000000007f8dd4] sysfs_kf_write+0x70/0xa4 > > > [c00000000bcc3af0] [c0000000007f7248] kernfs_fop_write_iter+0x1d0/0x2e0 > > > [c00000000bcc3b40] [c0000000006c9b08] vfs_write+0x27c/0x558 > > > [c00000000bcc3bf0] [c0000000006ca168] ksys_write+0x90/0x170 > > > [c00000000bcc3c40] [c000000000033248] system_call_exception+0xf8/0x290 > > > [c00000000bcc3e50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec > > > > > > > > > A git bisect pointed this regression to be introduced via [1] that added > > > a mechanism to create device tree nodes for parent PCI bridges when a > > > PCI device is hot-plugged. > > > > > > The Oops is caused when `pci_stop_dev()` tries to remove a non-existing > > > device-tree node associated with the pci_dev that was earlier > > > hot-plugged and was attached under a pci-bridge. The PCI dev header > > > `dev->hdr_type` being 0, results a conditional check done with > > > `pci_is_bridge()` into false. Consequently, a call to > > > `of_pci_make_dev_node()` to create a device node is never made. When at > > > a later point in time, in the device node removal path, a memcpy is > > > attempted in `__of_changeset_entry_invert()`; since the device node was > > > never created, results in an Oops due to kernel read access to a bad > > > address. > > > > > > To fix this issue, the patch updates `of_changeset_create_node()` to > > > allocate a new node only when the device node doesn't exist and init it > > > in case it does already. Also, introduce `of_pci_free_node()` to be > > > called to only revert and destroy the changeset device node that was > > > created via a call to `of_changeset_create_node()`. > > > > > > [1] commit 407d1a51921e ("PCI: Create device tree node for bridge") > > > > > > Fixes: 407d1a51921e ("PCI: Create device tree node for bridge") > > > Reported-by: Kowshik Jois B S > > > Signed-off-by: Lizhi Hou > > > Signed-off-by: Amit Machhiwal > > > --- > > > Changes since v1: > > > * Included Lizhi's suggested changes on V1 > > > * Fixed below two warnings from Lizhi's changes and rearranged the cleanup > > > part a bit in `of_pci_make_dev_node` > > > drivers/pci/of.c:611:6: warning: no previous prototype for ‘of_pci_free_node’ [-Wmissing-prototypes] > > > 611 | void of_pci_free_node(struct device_node *np) > > > | ^~~~~~~~~~~~~~~~ > > > drivers/pci/of.c: In function ‘of_pci_make_dev_node’: > > > drivers/pci/of.c:696:1: warning: label ‘out_destroy_cset’ defined but not used [-Wunused-label] > > > 696 | out_destroy_cset: > > > | ^~~~~~~~~~~~~~~~ > > > * V1: https://lore.kernel.org/all/20240703141634.2974589-1-amachhiw@linux.ibm.com/ > > > > > > drivers/of/dynamic.c | 16 ++++++++++++---- > > > drivers/of/unittest.c | 2 +- > > > drivers/pci/bus.c | 3 +-- > > > drivers/pci/of.c | 39 ++++++++++++++++++++++++++------------- > > > drivers/pci/pci.h | 2 ++ > > > include/linux/of.h | 1 + > > > 6 files changed, 43 insertions(+), 20 deletions(-) > > > > > > diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c > > > index dda6092e6d3a..9bba5e82a384 100644 > > > --- a/drivers/of/dynamic.c > > > +++ b/drivers/of/dynamic.c > > > @@ -492,21 +492,29 @@ struct device_node *__of_node_dup(const struct device_node *np, > > > * a given changeset. > > > * > > > * @ocs: Pointer to changeset > > > + * @np: Pointer to device node. If null, allocate a new node. If not, init an > > > + * existing one. > > > * @parent: Pointer to parent device node > > > * @full_name: Node full name > > > * > > > * Return: Pointer to the created device node or NULL in case of an error. > > > */ > > > struct device_node *of_changeset_create_node(struct of_changeset *ocs, > > > + struct device_node *np, > > > struct device_node *parent, > > > const char *full_name) > > > { > > > - struct device_node *np; > > > int ret; > > > > > > - np = __of_node_dup(NULL, full_name); > > > - if (!np) > > > - return NULL; > > > + if (!np) { > > > + np = __of_node_dup(NULL, full_name); > > > + if (!np) > > > + return NULL; > > > + } else { > > > + of_node_set_flag(np, OF_DYNAMIC); > > > + of_node_set_flag(np, OF_DETACHED); > > Are we going to rename the function to > > of_changeset_create_or_maybe_modify_node()? No. The functions here are > > very clear in that they allocate new objects and don't reuse what's > > passed in. > > Ok. How about keeping of_changeset_create_node unchanged. > > Instead, call kzalloc(), of_node_init() and of_changeset_attach_node() > > in of_pci_make_dev_node() directly. > > A similar example is dlpar_parse_cc_node(). > > > Does this sound better? No, because really that code should be re-written using of_changeset API. My suggestion is add a data pointer to struct of_changeset and then set that to something to know the data ptr is a changeset and is your changeset. Rob