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    Subject[PATCH v5] init: Disable defaults if init= fails
    Date
    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 makes a failure to run the specified init= process be fatal.

    As a temporary measure, users can set CONFIG_INIT_FALLBACK=y to
    preserve the old behavior. If no one speaks up, we can remove that
    option entirely after a release or two.

    Signed-off-by: Andy Lutomirski <luto@amacapital.net>
    ---

    Changes from v4:
    - Update the panic message (sorry for the noise)

    Changes from v3:
    - Get rid of the strictinit option. Now the new behavior is the default
    unless CONFIG_INIT_FALLBACK=y (Rob Landley)

    Changes from v2:
    - Improve docs further, to leave the door open to giving strictinit
    some sensible semantics if init= is not set.
    - Improve error output in the failure case (Shuah Khan).

    Changes from v1:
    - Add missing "if" to the docs (Randy Dunlap)

    init/Kconfig | 11 +++++++++++
    init/main.c | 7 ++++++-
    2 files changed, 17 insertions(+), 1 deletion(-)

    diff --git a/init/Kconfig b/init/Kconfig
    index e84c6423a2e5..063029a1556f 100644
    --- a/init/Kconfig
    +++ b/init/Kconfig
    @@ -1299,6 +1299,17 @@ source "usr/Kconfig"

    endif

    +config INIT_FALLBACK
    + bool "Fall back to defaults if init= parameter is bad"
    + help
    + If enabled, the kernel will try the default init binaries if an
    + explicit request from the init= parameter fails.
    +
    + This is a temporary measure to allow broken configurations
    + to continue to boot.
    +
    + If unsure, say N.
    +
    config CC_OPTIMIZE_FOR_SIZE
    bool "Optimize for size"
    help
    diff --git a/init/main.c b/init/main.c
    index bb1aed928f21..2bd6105e5dc5 100644
    --- a/init/main.c
    +++ b/init/main.c
    @@ -960,8 +960,13 @@ 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") ||
    --
    1.9.3


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