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Re: [Xen-devel] [PATCH v4 3/4] libxl: call hotplug scripts from libxl for vbd

Ian Campbell escribiÃ:
On Mon, 2012-05-14 at 13:38 +0100, Roger Pau Monne wrote:
+# Hack to prevent the execution of hotplug scripts from udev if the domain
+# has been launched from libxl
+if [ -n "${UDEV_CALL}" ]&&   \
+   `xenstore-read "libxl/disable_udev">/dev/null 2>&1`; then
This reads something from xenstore and executes it as a shell command!
(Also it will go wrong if the value read is empty eg becaue the key
doesn't exist.)
Are you sure about this? This command never returns anything, because it
is redirected to /dev/null, so we only evaluate if it is able to read
libxl/disable_udev. If libxl/disable_udev exists this test is passed.

You don't need the backticks for that though. With the backticks it will
execute whatever happens to be in the key -- I guess it's something
quite benign right now or you'd have seen errors.

Yes, it's not the first time that I've made that mistake. Since it never returns anything I guess that's why I never saw any errors.

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