linux-kernel - Re: nios2 crash due to 'init/main.c: extract early boot entropy from the passed cmdline'

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Message-ID: <CAGXu5j+JAuxdhuWfhXgq8rGtnJgM8zzGuY-i3sFr-eaPH7W5PQ@mail.gmail.com>
Date:   Mon, 11 Sep 2017 09:36:00 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Daniel Micay <danielmicay@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ley Foon Tan <lftan@...era.com>,
        nios2-dev@...ts.rocketboards.org,
        Laura Abbott <labbott@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: nios2 crash due to 'init/main.c: extract early boot entropy from
 the passed cmdline'

On Sat, Sep 9, 2017 at 8:58 PM, Guenter Roeck <linux@...ck-us.net> wrote:
> Hi,
>
> I noticed that nios2 images crash in mainline. Bisect points to commit
> 33d72f3822d7 ("init/main.c: extract early boot entropy from the passed
> cmdline").  Bisect log is attached.
>
> As far as I can see, the problem is seen because add_device_randomness()
> calls random_get_entropy(). However, the underlying timer function
> used by the nios2 architecture (nios2_timer_read) is not yet initialized,
> causing a NULL pointer access and crash. A sample crash log is at
>         http://kerneltests.org/builders/qemu-nios2-master/builds/175/steps/qemubuildcommand/logs/stdio

Oh, yikes. Do you have a full call trace? (Does this come through
get_cycles() or via the It seems like we could either initialize the
timer earlier or allow it to fall back when not initialized...

-Kees

>
> Guenter
>
> ---
> # bad: [4dfc2788033d30dfccfd4268e06dd73ce2c654ed] Merge tag 'iommu-updates-v4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu
> # good: [5969d1bb3082b41eba8fd2c826559abe38ccb6df] Merge branch 'gperf-removal'
> git bisect start 'HEAD' '5969d1bb3082'
> # bad: [fbd01410e89a66f346ba1b3c0161e1198449b746] Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
> git bisect bad fbd01410e89a66f346ba1b3c0161e1198449b746
> # good: [0d519f2d1ed1f11e49abc88cfcf6cf13b83ba14c] Merge tag 'pci-v4.14-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci
> git bisect good 0d519f2d1ed1f11e49abc88cfcf6cf13b83ba14c
> # bad: [229cf16d3c8ac2e9b082c223fd0e619dc8f62cc1] sh: defconfig: cleanup from old Kconfig options
> git bisect bad 229cf16d3c8ac2e9b082c223fd0e619dc8f62cc1
> # good: [1caffba9db4aa27c3e7ebc05668afca1f991ab8d] drivers/scsi/sym53c8xx_2/sym_hipd.c: convert to use memset32
> git bisect good 1caffba9db4aa27c3e7ebc05668afca1f991ab8d
> # good: [7c61bd6983b185272315722787cceacf5f5d2e7d] lib/cmdline.c: remove meaningless comment
> git bisect good 7c61bd6983b185272315722787cceacf5f5d2e7d
> # bad: [718b303b49893d8f9dd469f710d76f77673bd35d] autofs: use AUTOFS_DEV_IOCTL_SIZE
> git bisect bad 718b303b49893d8f9dd469f710d76f77673bd35d
> # good: [9367bb730e4d9d85a8911a08a3542ec2aa873d37] binfmt_flat: delete two error messages for a failed memory allocation in decompress_exec()
> git bisect good 9367bb730e4d9d85a8911a08a3542ec2aa873d37
> # bad: [e54c7bcbf14a25dc3a913b4c808b52121c522e9b] autofs: make disc device user accessible
> git bisect bad e54c7bcbf14a25dc3a913b4c808b52121c522e9b
> # bad: [33d72f3822d7ff8a9e45bd7413c811085cb87aa5] init/main.c: extract early boot entropy from the passed cmdline
> git bisect bad 33d72f3822d7ff8a9e45bd7413c811085cb87aa5
> # good: [121388a31362b0d3176dc1190ac8064b98a61b20] init: move stack canary initialization after setup_arch
> git bisect good 121388a31362b0d3176dc1190ac8064b98a61b20
> # first bad commit: [33d72f3822d7ff8a9e45bd7413c811085cb87aa5] init/main.c: extract early boot entropy from the passed cmdline



-- 
Kees Cook
Pixel Security