linux-kernel - memcpy without considering the get_zeroed

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Date:   Tue, 21 Mar 2017 03:35:30 +0100
From:   Peter Teoh <htmldeveloper@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Subject: memcpy without considering the get_zeroed_page() size returned

https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/vdso.c

/* kuser helpers */
memcpy((void *)vpage + 0x1000 - kuser_sz, __kuser_helper_start,
kuser_sz);
/* sigreturn code */
memcpy((void *)vpage + AARCH32_KERN_SIGRET_CODE_OFFSET,
__aarch32_sigret_code_start, sigret_sz);

I am just curious: depending on the configuration, will it ever
happened that get_zeroed_page() ever produce less amount of memory for
the above memcpy() operation to be successful? Ie, why the offset of
0x1000 is done without ever considering the actual amount of memory
allocated?

Please email me direct (no on LKML mailing list).