Hi,
On 4/23/23 11:07, thomas@xxxxxxxx wrote:
> On 2023-04-20 11:54:46-0500, Jorge Lopez wrote:
>> ---
>> .../x86/hp/hp-bioscfg/passwdobj-attributes.c | 669 ++++++++++++++++++
>> 1 file changed, 669 insertions(+)
>> create mode 100644 drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c
>>
>> diff --git a/drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c b/drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c
>> new file mode 100644
>> index 000000000000..c03b3a71e9c4
>> --- /dev/null
>> +++ b/drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c
<snip>
>> +static ssize_t current_password_store(struct kobject *kobj,
>> + struct kobj_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + char *p, *buf_cp;
>> + int id, ret = 0;
>> +
>> + buf_cp = kstrdup(buf, GFP_KERNEL);
>> + if (!buf_cp) {
>> + ret = -ENOMEM;
>> + goto exit_password;
>> + }
>> +
>> + p = memchr(buf_cp, '\n', count);
>> +
>> + if (p != NULL)
>> + *p = '\0';
>
> This will also accept input like "foo\nbar" and truncate away the "bar".
That is true, but stripping '\n' at the end is a pretty standard
pattern for sysfs attr store functions since users will e.g.
often do:
echo one-string-out-of-a-few-valid-strings > /sys/.../some-enum-attr
Where to actually write the real valid string the user should do:
echo -n one-string-out-of-a-few-valid-strings > /sys/.../some-enum-attr
See e.g.:
drivers/platform/x86/dell/dell-wmi-sysman/passobj-attributes.c new_password_store()
which does the exact same thing.
The stripping of '\n' is often taken care of by various kernel
helpers for sysfs attr.
> For something like a password it seems errorprone to try to munge the
> value.
Almost all password input dialogs including the actual BIOS password
input dialog will consider the enter key / a new-line to mean
"end-of-password, please validate the password inputted so far"
So I don't think this is really a problem. With that said we
could make this more robust (and maybe also change the Dell
code to match) by doing:
len = strlen(buf_cp);
if (len && buf_cp[len - 1] == '\n')
buf_cp[len - 1] = 0;
To ensure that we only ever strip a leading '\n'
and not one in the middle of the buffer.
Regards,
Hans
