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

[Myron Stowe <myron.stowe@redhat.com>]

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@marvell.com>
Signed-off-by: Myron Stowe <myron.stowe@redhat.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;