Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752433AbdIKRfT (ORCPT ); Mon, 11 Sep 2017 13:35:19 -0400 Received: from mail-pg0-f54.google.com ([74.125.83.54]:33242 "EHLO mail-pg0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752064AbdIKRfS (ORCPT ); Mon, 11 Sep 2017 13:35:18 -0400 X-Google-Smtp-Source: ADKCNb4+aHWDfRkBVuqNBe4Sh8K3G4XAkrH+27Xq8TixLxGbeM7vj3BPKRYkD2yTEqFkTgAgvEedtg== Date: Mon, 11 Sep 2017 10:35:16 -0700 From: Guenter Roeck To: Kees Cook Cc: Daniel Micay , LKML , Ley Foon Tan , nios2-dev@lists.rocketboards.org, Laura Abbott , Andrew Morton Subject: Re: nios2 crash due to 'init/main.c: extract early boot entropy from the passed cmdline' Message-ID: <20170911173516.GB27315@roeck-us.net> References: <20170910035815.GA9834@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3745 Lines: 82 On Mon, Sep 11, 2017 at 09:36:00AM -0700, Kees Cook wrote: > On Sat, Sep 9, 2017 at 8:58 PM, Guenter Roeck 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... > nios2 doesn't give me a traceback. I followed it by adding debug messages. The code path is through get_cycles(). On nios2: static u64 nios2_timer_read(struct clocksource *cs) { struct nios2_clocksource *nios2_cs = to_nios2_clksource(cs); unsigned long flags; u32 count; local_irq_save(flags); count = read_timersnapshot(&nios2_cs->timer); // <- not initialized local_irq_restore(flags); /* Counter is counting down */ return ~count; } cycles_t get_cycles(void) { return nios2_timer_read(&nios2_cs.cs); } EXPORT_SYMBOL(get_cycles); Guenter > -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