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platform/tests: don't attempt to mount anything to /sys/devices

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More recent kernels won't allow that in userns when /sys itself
is read-only.
This commit is contained in:
Lubomir Rintel 2016-10-17 15:16:55 +02:00
parent 0acdcc348c
commit 2c43862b2d
1 changed files with 32 additions and 18 deletions
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50
src/platform/tests/test-common.c
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@ -1620,32 +1620,46 @@ main (int argc, char **argv)
g_error ("unshare(CLONE_NEWNET|CLONE_NEWNS) failed with %s (%d)", strerror (errsv), errsv);
}
/* Mount our /sys instance, so that gudev sees only our devices.
* Needs to be read-only, because we don't run udev. */
/* Below we need a read-only /sys (to signal that we're in an environment
* we don't have udev and writable /sys/devices so that we still are able
* to test device classes that modify the device attributes (such as bridges).
*
* We use two sysfs instances to achieve this, binding the /device subtree
* of the writeable one to the read-only one.
*
* We abuse a /sys/kernel/debug for our temporary writable sysfs mount,
* just because it's guarranteed to exist and mounts are allowed there even
* after the sysfs mount point hardening [linux 0cbee99269]. It's just in
* our mount namespace, we release it quickly and don't need debugfs anyway...
* An alrernative would be to create a temporary directory, but that seems
* like an overkill. */
/* Make the mounts below /sys private to our namespace. Other mounts
* wouldn't be permitted for good reasons. */
mount (NULL, "/sys", "sysfs", MS_SLAVE, NULL);
/* Mount the read-only sysfs. */
if (mount ("sys", "/sys", "sysfs", MS_RDONLY, NULL) != 0) {
errsv = errno;
g_error ("mount(\"/sys\") failed with %s (%d)", strerror (errsv), errsv);
}
/* Create a writable /sys/devices tree. This makes it possible to run tests
* that modify values via sysfs (such as bridge forward delay). */
if (mount ("sys", "/sys/devices", "sysfs", 0, NULL) != 0) {
/* Create the writable /sys/devices tree. */
if (mount ("sys", "/sys/kernel/debug", "sysfs", 0, NULL) != 0) {
errsv = errno;
g_error ("mount(\"/sys/devices\") failed with %s (%d)", strerror (errsv), errsv);
g_error ("mount(\"/sys/devices/k\") failed with %s (%d)", strerror (errsv), errsv);
}
if (mount (NULL, "/sys/devices", "sysfs", MS_REMOUNT, NULL) != 0) {
/* Read-write remount failed. Never mind, we're probably just a root in
* our user NS. */
if (umount ("/sys/devices") != 0) {
errsv = errno;
g_error ("umount(\"/sys/devices\") failed with %s (%d)", strerror (errsv), errsv);
}
} else {
if (mount ("/sys/devices/devices", "/sys/devices", "sysfs", MS_BIND, NULL) != 0) {
errsv = errno;
g_error ("mount(\"/sys\") failed with %s (%d)", strerror (errsv), errsv);
}
/* Bind mound the writable device tree to the read-only sysfs. */
if (mount ("/sys/kernel/debug/devices", "/sys/devices", "sysfs", MS_BIND, NULL) != 0) {
errsv = errno;
g_error ("mount(\"/sys\") failed with %s (%d)", strerror (errsv), errsv);
}
/* Release the temporary mount now that we bound the /devices subtree. */
if (umount ("/sys/kernel/debug") != 0) {
errsv = errno;
g_error ("umount(\"/sys/kernel/debug\") failed with %s (%d)", strerror (errsv), errsv);
}
}