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    Subject[PATCH 3.16 065/305] printk: Fix panic caused by passing log_buf_len to command line
    3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: He Zhe <zhe.he@windriver.com>

    commit 277fcdb2cfee38ccdbe07e705dbd4896ba0c9930 upstream.

    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.

    Link: http://lkml.kernel.org/r/1538239553-81805-1-git-send-email-zhe.he@windriver.com
    Cc: rostedt@goodmis.org
    Cc: linux-kernel@vger.kernel.org
    Signed-off-by: He Zhe <zhe.he@windriver.com>
    Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Signed-off-by: Petr Mladek <pmladek@suse.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    kernel/printk/printk.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/kernel/printk/printk.c
    +++ b/kernel/printk/printk.c
    @@ -837,7 +837,12 @@ static unsigned long __initdata new_log_
    /* save requested log_buf_len since it's too early to process it */
    static int __init log_buf_len_setup(char *str)
    {
    - unsigned size = memparse(str, &str);
    + unsigned int size;
    +
    + if (!str)
    + return -EINVAL;
    +
    + size = memparse(str, &str);

    if (size)
    size = roundup_pow_of_two(size);
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