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switch-root: remount to MS_PRIVATE

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The kernel does not allow switching roots if things are mounted
MS_SHARED. As a work-around, remount things MS_PRIVATE before switching
roots.

This should be fixed in the kernel for good.

https://bugzilla.redhat.com/show_bug.cgi?id=847418
This commit is contained in:
Lennart Poettering
2012-08-12 01:31:03 +02:00
parent dbf61afb29
commit f47fc35555
2 changed files with 17 additions and 9 deletions
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src/core/shutdown.c
+8 -9
View File
@@ -104,15 +104,14 @@ static int pivot_to_new_root(void) {
return -errno;
}
/*
In case some evil process made "/" MS_SHARED
It works for pivot_root, but the ref count for the root device
is not decreasing :-/
*/
if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) {
log_error("Failed to make \"/\" private mount %m");
return -errno;
}
/* Work-around for a kernel bug: for some reason the kernel
* refuses switching root if any file systems are mounted
* MS_SHARED. Hence remount them MS_PRIVATE here as a
* work-around.
*
* https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
log_warning("Failed to make \"/\" private mount: %m");
if (pivot_root(".", "oldroot") < 0) {
log_error("pivot failed: %m");
src/core/switch-root.c
+9
View File
@@ -56,6 +56,15 @@ int switch_root(const char *new_root) {
goto fail;
}
/* Work-around for a kernel bug: for some reason the kernel
* refuses switching root if any file systems are mounted
* MS_SHARED. Hence remount them MS_PRIVATE here as a
* work-around.
*
* https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
log_warning("Failed to make \"/\" private mount: %m");
NULSTR_FOREACH(i, move_mounts) {
char new_mount[PATH_MAX];
struct stat sb;