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SubjectRe: [PATCH v3 1/2] printk: Fix panic caused by passing log_buf_len to command line
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On 2018年09月23日 00:19, Steven Rostedt wrote:
> On Sat, 22 Sep 2018 23:40:51 +0800
> <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>
>> Cc: stable@vger.kernel.org
> I just tried this on a 2.6.32 kernel, and it crashes there. I guess
> this goes farther back than git history goes.
>
> Perhaps it should be commented that this bug has been here since
> creation of (git) time.

I did a try on 2.6.32. It passed. Actually this bug only happens on
early_param(not __setup) which is introduced since v3.0. The oldest
LTS version is 3.16 now. Should I send v4 and add a statement about
the supported version range in commit log?

>
>
>> Cc: pmladek@suse.com
>> Cc: sergey.senozhatsky@gmail.com
>> Cc: rostedt@goodmis.org
>> ---
>> v2:
>> Split out the addition of pr_fmt and the unsigned update
> Which unsigned update? As it does switch to unsigned to "unsigned int",
> but that change is fine to me with this.

No problem. It's the history of v2.

In v1 you suggested "unsigned int size" should be in a separate patch and
I did that in v2. Then Sergey suggested "unsigned int size" should be in the
1/2 patch to avoid checkpatch.pl warning. With your conformation, I add it
back here in v3.

Thanks,
Zhe

>
>> v3:
>> Use more clear error info
>> Change unsigned to unsigned in to avoid checkpatch.pl warning
>>
>> kernel/printk/printk.c | 9 ++++++++-
>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index 9bf5404..d9821c0 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -1048,7 +1048,14 @@ static void __init log_buf_len_update(unsigned size)
>> /* 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;
> I'm OK with the int update too, as its low risk.
>
> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
>
> -- Steve
>
>> +
>> + if (!str) {
>> + pr_err("boot command line parameter value not provided\n");
>> + return -EINVAL;
>> + }
>> +
>> + size = memparse(str, &str);
>>
>> log_buf_len_update(size);
>>
>

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