Messages in this thread | | | Date | Wed, 17 Nov 2004 09:31:54 +1100 | From | Paul Mackerras <> | Subject | Re: [patch 0/4] Cleanup file_count usage |
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Ravikiran G Thirumalai writes:
> 2. Read to f_count at drivers/net/ppp_generic.c: > The PPPIOCDETACH ioctl is failed if the device fd is duped and > being polled by another process -- which is determined by a read > to f_count. The comments in the code indicate that the PPPIOCDETACH > ioctl should be junked and userland can use a workaround > by closing the fd and reopening /dev/ppp. I can make a patch to junk > PPPIOCDETACH, but is it okay to break binary compatibility? Paul?
I would very much rather not break binary compatibility. People using ppp-2.4.2 or ppp-2.4.3 won't be affected by this change, but ppp-2.4.2 was released in January this year and I wouldn't be surprised if some people are still using ppp-2.4.1 (or even ppp-2.4.0), which would be affected.
I suggest that as a temporary compromise, we keep PPPIOCDETACH but make it zero file->private_data without freeing the ppp structure that it points to. That will cause a memory leak but will avoid the possibility of using that memory after it is freed (in the case where the descriptor has been dup'd and another process is doing a poll on it).
We should make the kernel whinge loudly when anyone uses PPPIOCDETACH, too. If/when 2.7.0 comes along we can remove it.
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