Re: [PATCH] fs/eventpoll: error handling micro-cleanup

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Davide Libenzi wrote:
On Sun, 1 Oct 2006, Jeff Garzik wrote:

Davide Libenzi wrote:

I just tried a `find /usr/src/linux-2.6.16/ -type f -exec grep -H -C 2
PTR_ERR {} \;`
and looked at the cases where the error variable is assigned in any case
before the test. Same code pattern as, like:

error = -EFAULT;
if (copy_from_user(...))
	goto kaboom;
No, that's quite different.  I'm talking about

	ptr = get_a_pointer_from_somewhere()
	error = PTR_ERR(ptr)

See the difference?  The error variable is directly assigned from a
potentially-valid pointer.

So? Is PTR_ERR() defined and documented in a way that, if called with a valid pointer, has an unexpected/faulty behaviour?

When called with a valid pointer, the value assigned to the return-code integer is essentially a random number.


Again, I don't care either ways, but don't tell me you're not sure about the countless occurrences. Take a look at:

`find $LINUXSRC -type f -exec grep -H -C 2 PTR_ERR {} \;`

Perhaps 1 out of every 100 or so hits from this find(1) is unprotected by IS_ERR(). IOW, what I've been describing here is quite rare.

	Jeff



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