On Fri, Feb 18, 2011 at 10:54:56AM +0900, Simon Horman wrote:
> In "PM QoS: Correct pr_debug() misuse and improve parameter checks"
> the parsing of the ASCII hex value was tightened. Unfortunately
> it was tightened to the point where no value is valid.
How is it of no value? Can you not sent a 10 char string with a
zero-byte end of string maker?
Is expecting the c-string marker in the interface a bad idea that needs
fixing?
> Root of the problem seems to lie in wheather the ASCII hex is followed
> by a '\n' or not. My reading of the documentation is that the '\n' should
> not be present. However the code previously only accepted that version.
> The current code accepts neither. My fix is to accept both.
The documentation says it should be a 10byte string.
"Alternatively the user mode program could write a hex string for the
value using 10 char long format e.g. "0x12345678". This translates to a
pm_qos_update_request call."
When I wrote the code I was thinking that a c-string that has a zero
byte end of string maker. note: a new line character is not implied
anywhere.
However; reading the documentation it is somewhat ambiguous the buffer
is 10 bytes or 11.
We should tighten up the Documentation and make the code match it.
I don't like the 10 or 11 byte buffer logic. It should be one or the
other and not include any new line character.
What do you want the documentation to read?
--mark
>
> Cc: Mark Gross <markgross@xxxxxxxxxxx>
> Cc: Dan Carpenter <error27@xxxxxxxxx>
> Cc: Rafael J. Wysocki <rjw@xxxxxxx>
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
>
> ---
> This appears to have been introduced around 2.6.36-rc4.
> And was an @stable patch. As such I believe this change
> is stable material.
> ---
> kernel/pm_qos_params.c | 7 ++++---
> 1 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
> index aeaa7f8..98a34ea 100644
> --- a/kernel/pm_qos_params.c
> +++ b/kernel/pm_qos_params.c
> @@ -387,10 +387,11 @@ static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
> if (count == sizeof(s32)) {
> if (copy_from_user(&value, buf, sizeof(s32)))
> return -EFAULT;
> - } else if (count == 11) { /* len('0x12345678/0') */
> - if (copy_from_user(ascii_value, buf, 11))
> + } else if (count == 11 || count == 10) { /* len('0x12345678\n') or
> + * len('0x12345678') */
> + if (copy_from_user(ascii_value, buf, count))
> return -EFAULT;
> - if (strlen(ascii_value) != 10)
> + if (strlen(ascii_value) != count)
> return -EINVAL;
> x = sscanf(ascii_value, "%x", &value);
> if (x != 1)
> --
> 1.7.2.3
>
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