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Commit 6ef4536e authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Linus Torvalds
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init: allow CONFIG_INIT_FALLBACK=n to disable defaults if init= fails 



If a user puts init=/whatever on the command line and /whatever can't be
run, then the kernel will try a few default options before giving up.  If
init=/whatever came from a bootloader prompt, then this is unexpected but
probably harmless.  On the other hand, if it comes from a script (e.g.  a
tool like virtme or perhaps a future kselftest script), then the fallbacks
are likely to exist, but they'll do the wrong thing.  For example, they
might unexpectedly invoke systemd.

This adds a config option CONFIG_INIT_FALLBACK.  If unset, then a failure
to run the specified init= process be fatal.

The tentative plan is to remove CONFIG_INIT_FALLBACK for 3.20.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Cc: Rob Landley <rob@landley.net>
Cc: Chuck Ebbert <cebbert.lkml@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 52f5592e

init/Kconfig

+16 −0
Original line number Diff line number Diff line
@@ -1280,6 +1280,22 @@ source "usr/Kconfig" 


endif



config INIT_FALLBACK

	bool "Fall back to defaults if init= parameter is bad"

	default y

	help

	  If enabled, the kernel will try the default init binaries if an

	  explicit request from the init= parameter fails.



	  This can have unexpected effects.  For example, booting

	  with init=/sbin/kiosk_app will run /sbin/init or even /bin/sh

	  if /sbin/kiosk_app cannot be executed.



	  The default value of Y is consistent with historical behavior.

	  Selecting N is likely to be more appropriate for most uses,

	  especially on kiosks and on kernels that are intended to be

	  run under the control of a script.



config CC_OPTIMIZE_FOR_SIZE

	bool "Optimize for size"

	help

init/main.c

+6 −1
Original line number Diff line number Diff line
@@ -952,8 +952,13 @@ static int __ref kernel_init(void *unused) 
		ret = run_init_process(execute_command);

		if (!ret)

			return 0;

#ifndef CONFIG_INIT_FALLBACK

		panic("Requested init %s failed (error %d).",

		      execute_command, ret);

#else

		pr_err("Failed to execute %s (error %d).  Attempting defaults...\n",

		       execute_command, ret);

#endif

	}

	if (!try_to_run_init_process("/sbin/init") ||

	    !try_to_run_init_process("/etc/init") ||