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Date:   Mon, 8 Oct 2018 15:01:40 +0200
From:   Petr Mladek <pmladek@suse.com>
To:     zhe.he@windriver.com
Cc:     sergey.senozhatsky@gmail.com, rostedt@goodmis.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/4] printk: Fix panic caused by passing log_buf_len
 to command line
Message-ID: <20181008130140.elxnip7npkcd6wpq@pathway.suse.cz>
References: <1538239553-81805-1-git-send-email-zhe.he@windriver.com>
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On Sun 2018-09-30 00:45:50, zhe.he@windriver.com wrote:
> From: He Zhe <zhe.he@windriver.com>
> 
> log_buf_len_setup does not check input argument before passing it to
> simple_strtoull. The argument would be a NULL pointer if "log_buf_len",
> without its value, is set in command line and thus causes the following
> panic.
> 
> PANIC: early exception 0xe3 IP 10:ffffffffaaeacd0d error 0 cr2 0x0
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc4-yocto-standard+ #1
> [    0.000000] RIP: 0010:_parse_integer_fixup_radix+0xd/0x70
> ...
> [    0.000000] Call Trace:
> [    0.000000]  simple_strtoull+0x29/0x70
> [    0.000000]  memparse+0x26/0x90
> [    0.000000]  log_buf_len_setup+0x17/0x22
> [    0.000000]  do_early_param+0x57/0x8e
> [    0.000000]  parse_args+0x208/0x320
> [    0.000000]  ? rdinit_setup+0x30/0x30
> [    0.000000]  parse_early_options+0x29/0x2d
> [    0.000000]  ? rdinit_setup+0x30/0x30
> [    0.000000]  parse_early_param+0x36/0x4d
> [    0.000000]  setup_arch+0x336/0x99e
> [    0.000000]  start_kernel+0x6f/0x4ee
> [    0.000000]  x86_64_start_reservations+0x24/0x26
> [    0.000000]  x86_64_start_kernel+0x6f/0x72
> [    0.000000]  secondary_startup_64+0xa4/0xb0
> 
> This patch adds a check to prevent the panic.
> 
> Signed-off-by: He Zhe <zhe.he@windriver.com>

JFYI, I have pushed this patch into printk.git, branch for-4.20.

Best Regards,
Petr