From 6ef4536e2f19c4dba3637413d73ea00b19764bc0 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 10 Dec 2014 15:52:19 -0800 Subject: [PATCH] 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: Andy Lutomirski Cc: Rob Landley Cc: Chuck Ebbert Cc: Randy Dunlap Cc: Shuah Khan Cc: Frank Rowand Cc: Josh Triplett Acked-by: Rusty Russell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/Kconfig | 16 ++++++++++++++++ init/main.c | 7 ++++++- 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/init/Kconfig b/init/Kconfig index 7e9fbd48e2ab..9afb971497f4 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -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 diff --git a/init/main.c b/init/main.c index d2e4ead4891f..ca380ec685de 100644 --- a/init/main.c +++ b/init/main.c @@ -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); + execute_command, ret); +#endif } if (!try_to_run_init_process("/sbin/init") || !try_to_run_init_process("/etc/init") || -- 2.30.2