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SubjectStrangest bug
Hi,

I am fairly new to kernel hacking, so forgive my stupidity. I have
encountered a very strange bug and need help from someone who knows
a lot about the kernel.

Description of the problem: A process passes a pointer allocated in the
user space to the kernel through a custom system call. This pointer is
then saved for future reference.

Upon an interrupt, a kernel routine uses this saved pointer with
copy_from_user() to obtain a copy of that structure. The problem is,
every now and then the values in the structure are bogus!

This is not due to memory corruption (in the user process, I
continuously print out the values, and they are fine). When I use
mlock() on the structure, then the problem no longer occurs (the copy
reflects accurate values). So the problem has something to do with
virtual addressing and paging...

If you can think of a reason why this might be happening, or how to fix
this, please help me. If you need additional bits of information, I'll
gladly supply it.

I am using RH 6.0 w/kernel 2.2.5.

Thank you in advance.

+------------------------+----------------------------------------+
| Stan Albright Rost | http://mdsp.bu.edu/prgrssor_html |
| AKA | "You want my advice? -- here it is: |
| "The Progressor" | Go and Work." |
+------------------------+----= Arkadiy and Boris Strugatskiy =---+


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