[LTP] [PATCH] syscalls/keyctl06: Print TFAIL if keyring_read() returns wrong size

[Eric Biggers <ebiggers3@gmail.com>]

On Wed, Oct 18, 2017 at 02:25:25PM +0800, Xiao Yang wrote:
> >It was actually pointed out yesterday that the short return value is a bug in
> >the kernel patch.  The documented behavior of keyctl_read() (as well as the
> >actual behavior for the other key types that implement it) is to return the full
> >count on a short read, rather than a short count.  It's not really intuitive but
> >I'm going to have to fix it with another kernel patch.
> Thanks for your explanation.
> Sorry, i misunderstood the expected return value before.
> 
> 
> >For now we probably should just make the test accept both return values:
> >
> >	if (TEST_RETURN != sizeof(key_serial_t)&&
> >	TEST_RETURN != sizeof(key_ids)) {
> >		tst_brk(TBROK, "KEYCTL_READ returned %ld but expected %zu or %zu",
> >			TEST_RETURN, sizeof(key_serial_t), sizeof(key_ids));
> >	}
> >
> >Then once there is another kernel patch, I'll update the test to reference that
> >commit too, and accept only TEST_RETURN == sizeof(key_ids).
> Could we update the test to check both return values? as below:
> if (TEST_RETURN != sizeof(key_ids)) {
> 	/* keyctl_read() should return the size of buffer required, rather than the size
> 	 * of data read into buffer. This bug was introduced by the commit:
> 	 * e645016abc80 ("KEYS: fix writing past end of user-supplied buffer in keyring_read()")
> 	 */
> 	if (TEST_RETURN == sizeof(key_serial_t)) {
> 		tst_brk(TFAIL, "KEYCTL_READ returned %ld but expected %zu",
> 			TEST_RETURN, sizeof(key_ids));
> 	}
> 
> 	tst_brk(TBROK, "KEYCTL_READ returned %ld but expected %zu",
> 		TEST_RETURN, sizeof(key_ids));
> }
> 
> We probably should expose the short return value as a bug, rather than ignore it.
> 

This will confuse people when the comment at the top of the file says
"regression test for commit e645016abc80", so people will waste time trying to
figure out why the test is still failing.  I'd prefer to wait to require the
full return value until I get a second fix applied, which can then be explicitly
referenced from the test.

Eric