Re: Either the IP masq code or my brain is broken.

Andi Kleen (ak@muc.de)
27 Oct 1998 08:06:19 +0100


In article <E0zXuV6-0004wI-00@devel2.axiom.internal>,
David Woodhouse <David.Woodhouse@mvhi.com> writes:
> To help me trace the recurring IP masquerade oopsen that people are seeing, I
> made this simple patch to add a call to verify_area() for the packet being
> demasqueraded, and whinge if it fails.

> Could anyone tell me why it keeps failing? (Where failing == printing my
> 'whinge' message.) The complaint is happening quite frequently, but the
> machine wasn't going down that often before, so it must be catching cases that
> didn't cause an oops (whinge once a minute vs. crash once a fortnight.)

It is bogus to call verify_area on kernel buffers - it only works for addresses
passed in from user space (except when you use set_fs(KERNEL_DS), but even
then it isn't a comprehensive check). Also note that verify_area in 2.1 is
mostly a nop, it only checks if the address is below the kernel segment
border.

For what address exactly does the oops occur?

-A.

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