RE: Writing to a const pointer: is this supposed to happen?

David Laight
2020-07-02T07:55:35Z

From: Kars Mulder
> Sent: 02 July 2020 00:03
> On Saturday, June 27, 2020 12:24 CEST, David Laight wrote:
> > The code quoted (using strset()) is almost certainly wrong.
> > The caller is unlikely to expect the input be modified.
> > Since it doesn't fault the string must be in read-write memory.
>
> I tried writing a patch that avoids the writing-to-const-pointer issue
> by using the less intrusive sscanf function instead of strsep. It might
> avoid a potential bug when somebody wrongly assumes that a
> kernel_param_ops.set function will not write to its const char* argument.

Hmm... sscanf() is also horrid.
Surprisingly difficult to use correctly.

It is usually best to use strchr() (and maybe str[c]scn())
to parse strings.
For numbers use whatever the kernels current 'favourite' implementation
of strtoul() is called.

David

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