linux-kernel - [PATCH] udevadm-info: Don't access sysfs 'resource<N>' files

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Date:	Sat, 16 Mar 2013 15:35:19 -0600
From:	Myron Stowe <myron.stowe@...hat.com>
To:	kay@...y.org
Cc:	linux-hotplug@...r.kernel.org, greg@...ah.com,
	alex.williamson@...hat.com, linux-pci@...r.kernel.org,
	yuxiangl@...vell.com, yxlraid@...il.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH] udevadm-info: Don't access sysfs 'resource<N>' files

Sysfs includes entries to memory that backs a PCI device's BARs, both I/O
Port space and MMIO.  This memory regions correspond to the device's
internal status and control registers used to drive the device.

Accessing these registers from userspace such as "udevadm info
--attribute-walk --path=/sys/devices/..." does can not be allowed as
such accesses outside of the driver, even just reading, can yield
catastrophic consequences.

Udevadm-info skips parsing a specific set of sysfs entries including
'resource'.  This patch extends the set to include the additional
'resource<N>' entries that correspond to a PCI device's BARs.

Reported-by: Xiangliang Yu <yuxiangl@...vell.com>
Signed-off-by: Myron Stowe <myron.stowe@...hat.com>
---

 src/udevadm-info.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/src/udevadm-info.c b/src/udevadm-info.c
index ee9b59f..298acb5 100644
--- a/src/udevadm-info.c
+++ b/src/udevadm-info.c
@@ -37,13 +37,18 @@ static bool skip_attribute(const char *name)
                 "uevent",
                 "dev",
                 "modalias",
-                "resource",
                 "driver",
                 "subsystem",
                 "module",
         };
         unsigned int i;
 
+        /*
+         * Skip any sysfs 'resource' entries, including 'resource<N>' entries
+         * that correspond to a device's I/O Port or MMIO space backed BARs.
+         */
+        if (strncmp((const char *)name, "resource", sizeof("resource")-1) == 0)
+                return true;
         for (i = 0; i < ARRAY_SIZE(skip); i++)
                 if (strcmp(name, skip[i]) == 0)
                         return true;

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