Re: [PATCH] fix sys cpumap for > 352 NR_CPUS

[Paul Jackson <pj@sgi.com>]

Rusty wrote:
> Then just use -1UL as the arg to scnprintf, if you don't have a real
> number.  That way the overflow will at least have a chance of detection
> in the sysfs code, which I think it should check in
> file.c:fill_read_buffer().  Greg?

That doesn't make sense.

My node_read_cpumap() routine is being passed a finite length buffer
into which it is supposed to put some characters.  Unless by contract
or passed value it knows the length of that buffer, it cannot safely
know how far it can write.

Apparently, from Andrews comments and from the line:

  buffer->page = (char *) get_zeroed_page(GFP_KERNEL);

in file.c:fill_read_buffer(), the length is PAGE_SIZE, by contract.

Greg - perhaps a comment in include/linux/sysdev.h, near the declarations
for the show() and store() routines, specifying the buffer sizing,
would be appropriate?

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                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373