linux-kernel - [RFC PATCH v2 02/11] PCI/P2PDMA: Avoid pci_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210311233142.7900-3-logang@deltatee.com>
Date:   Thu, 11 Mar 2021 16:31:32 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        Ira Weiny <iweiny@...el.com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jakowski Andrzej <andrzej.jakowski@...el.com>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [RFC PATCH v2 02/11] PCI/P2PDMA: Avoid pci_get_slot() which sleeps

In order to use upstream_bridge_distance_warn() from a dma_map function,
it must not sleep. However, pci_get_slot() takes the pci_bus_sem so it
might sleep.

In order to avoid this, try to get the host bridge's device from
bus->self, and if that is not set just get the first element in the
list. It should be impossible for the host bridges device to go away
while references are held on child devices, so the first element
should not change and this should be safe.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
 drivers/pci/p2pdma.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index bd89437faf06..2135fe69bb07 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -311,11 +311,15 @@ static const struct pci_p2pdma_whitelist_entry {
 static bool __host_bridge_whitelist(struct pci_host_bridge *host,
 				    bool same_host_bridge)
 {
-	struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0));
 	const struct pci_p2pdma_whitelist_entry *entry;
+	struct pci_dev *root = host->bus->self;
 	unsigned short vendor, device;
 
 	if (!root)
+		root = list_first_entry_or_null(&host->bus->devices,
+						struct pci_dev, bus_list);
+
+	if (!root || root->devfn)
 		return false;
 
 	vendor = root->vendor;
-- 
2.20.1