• Petr Mladek's avatar
    printk/console: Enhance the check for consoles using init memory · 5a814231
    Petr Mladek authored
    printk_late_init() is responsible for disabling boot consoles that
    use init memory. It checks the address of struct console for this.
    
    But this is not enough. For example, there are several early
    consoles that have write() method in the init section and
    struct console in the normal section. They are not disabled
    and could cause fancy and hard to debug system states.
    
    It is even more complicated by the macros EARLYCON_DECLARE() and
    OF_EARLYCON_DECLARE() where various struct members are set at
    runtime by the provided setup() function.
    
    I have tried to reproduce this problem and forced the classic uart
    early console to stay using keep_bootcon parameter. In particular
    I used earlycon=uart,io,0x3f8 keep_bootcon console=ttyS0,115200.
    The system did not boot:
    
    [    1.570496] PM: Image not found (code -22)
    [    1.570496] PM: Image not found (code -22)
    [    1.571886] PM: Hibernation image not present or could not be loaded.
    [    1.571886] PM: Hibernation image not present or could not be loaded.
    [    1.576407] Freeing unused kernel memory: 2528K
    [    1.577244] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
    
    The double lines are caused by having both early uart console and
    ttyS0 console enabled at the same time. The early console stopped
    working when the init memory was freed. Fortunately, the invalid
    call was caught by the NX-protexted page check and did not cause
    any silent fancy problems.
    
    This patch adds a check for many other addresses stored in
    struct console. It omits setup() and match() that are used
    only when the console is registered. Therefore they have
    already been used at this point and there is no reason
    to use them again.
    
    Link: http://lkml.kernel.org/r/1500036673-7122-3-git-send-email-pmladek@suse.com
    
    
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Matt Redfearn <matt.redfearn@imgtec.com>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Jiri Slaby <jslaby@suse.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
    Cc: "Fabio M. Di Nitto" <fdinitto@redhat.com>
    Cc: linux-serial@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    Reviewed-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
    5a814231
printk.c 79.4 KB