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 probably makes sense. 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 new option called strictinit. If init= and strictinit
are both set, and the init= binary is not executable, then the
kernel will panic immediately. If strictinit is set but init= is
not set, then strictinit will have no effect, because the only real
alternative would be to panic regardless of the contents of the root
fs.
Signed-off-by: Andy Lutomirski <l...@amacapital.net>
---
Documentation/kernel-parameters.txt | 8 ++++++++
init/main.c | 10 ++++++++++
2 files changed, 18 insertions(+)
diff --git a/Documentation/kernel-parameters.txt
b/Documentation/kernel-parameters.txt
index 10d51c2f10d7..60f8b3a7a506 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3236,6 +3236,14 @@ bytes respectively. Such letter suffixes can also be
entirely omitted.
stifb= [HW]
Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
+ strictinit [KNL,BOOT]
+ Normally, the kernel can't find the init binary
+ specified by rdinit= and/or init=, then it will
+ try several fallbacks. If strictinit is set
+ and the value specified by init= does not work,
+ then the kernel will panic instead.
+ This has no effect if init= is not specified.
+
sunrpc.min_resvport=
sunrpc.max_resvport=
[NFS,SUNRPC]
diff --git a/init/main.c b/init/main.c
index bb1aed928f21..4fd80dcef9d0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -131,6 +131,7 @@ static char *initcall_command_line;
static char *execute_command;
static char *ramdisk_execute_command;
+static bool strictinit;
/*
* Used to generate warnings if static_key manipulation functions are used
@@ -347,6 +348,13 @@ static int __init rdinit_setup(char *str)
}
__setup("rdinit=", rdinit_setup);
+static int __init strictinit_setup(char *str)
+{
+ strictinit = true;
+ return 1;
+}
+__setup("strictinit", strictinit_setup);
+
#ifndef CONFIG_SMP
static const unsigned int setup_max_cpus = NR_CPUS;
#ifdef CONFIG_X86_LOCAL_APIC
@@ -962,6 +970,8 @@ static int __ref kernel_init(void *unused)
return 0;
pr_err("Failed to execute %s (error %d). Attempting
defaults...\n",
execute_command, ret);
+ if (strictinit)
+ panic("Requested init failed and strictinit was set.");
}
if (!try_to_run_init_process("/sbin/init") ||
!try_to_run_init_process("/etc/init") ||
--
1.9.3
--
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