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

From: Kees Cook
Date: Mon Sep 11 2017 - 12:36:07 EST

On Sat, Sep 9, 2017 at 8:58 PM, Guenter Roeck <linux@xxxxxxxxxxxx> 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

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...


> Guenter
> ---
> # bad: [4dfc2788033d30dfccfd4268e06dd73ce2c654ed] Merge tag 'iommu-updates-v4.14' of git://
> # good: [5969d1bb3082b41eba8fd2c826559abe38ccb6df] Merge branch 'gperf-removal'
> git bisect start 'HEAD' '5969d1bb3082'
> # bad: [fbd01410e89a66f346ba1b3c0161e1198449b746] Merge git://
> git bisect bad fbd01410e89a66f346ba1b3c0161e1198449b746
> # good: [0d519f2d1ed1f11e49abc88cfcf6cf13b83ba14c] Merge tag 'pci-v4.14-changes' of git://
> 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