Re: [x86, kaslr] BUG: kernel boot hang

From: Kees Cook
Date: Tue Jan 14 2014 - 17:33:23 EST


On Tue, Jan 14, 2014 at 5:31 AM, Fengguang Wu <fengguang.wu@xxxxxxxxx> wrote:
> Greetings,
>
> I got the below dmesg and the first bad commit is
>
> commit 82fa9637a2ba285bcc7c5050c73010b2c1b3d803
> Author: Kees Cook <keescook@xxxxxxxxxxxx>
> AuthorDate: Thu Oct 10 17:18:16 2013 -0700
> Commit: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> CommitDate: Sun Oct 13 03:12:19 2013 -0700
>
> x86, kaslr: Select random position from e820 maps
>
> Counts available alignment positions across all e820 maps, and chooses
> one randomly for the new kernel base address, making sure not to collide
> with unsafe memory areas.
>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Link: http://lkml.kernel.org/r/1381450698-28710-5-git-send-email-keescook@xxxxxxxxxxxx
> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
>
> Note that there are many other warning/errors and it's not very
> reproducible, so this report might be wrong.
>
> ===================================================
> PARENT COMMIT NOT CLEAN. LOOK OUT FOR WRONG BISECT!
> ===================================================
>
> +-----------------------------------------------------------+--------------+--------------+
> | | 5bfce5ef55cb | 1955a14a5ba6 |
> +-----------------------------------------------------------+--------------+--------------+
> | boot_successes | 3948 | 0 |
> | boot_failures | 52 | 89 |
> | page_allocation_failure:order:,mode | 48 | 2 |
> | Out_of_memory:Kill_process | 7 | |
> | BUG:kernel_early_hang_without_any_printk_output | 1 | |
> | BUG:soft_lockup-CPU_stuck_for_s | 1 | |
> | WARNING:CPU:PID:at_kernel/locking/lockdep.c:check_flags() | 0 | 85 |
> | general_protection_fault:SMP_SMP | 0 | 1 |
> | RIP:__lock_acquire | 0 | 1 |
> | Kernel_panic-not_syncing:Fatal_exception | 0 | 1 |
> | BUG:kernel_boot_hang | 0 | 2 |
> | BUG:kernel_boot_crashed | 0 | 1 |
> +-----------------------------------------------------------+--------------+--------------+
>
> The last dmesg is
>
> [ 0.803796] Initramfs unpacking failed: junk in compressed archive

Can you tell me how the initrd for quantal-core-x86_64.cgz was built
in the qemu instances you're using? It seems like all the failures
point to a problem with how kASLR is interacting with the initrd.

Thanks,

-Kees

--
Kees Cook
Chrome OS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/