linux-kernel - Re: [PATCH] init: Use kcalloc() instead of kzalloc()

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Message-ID: <20251002023657.GF39973@ZenIV>
Date: Thu, 2 Oct 2025 03:36:57 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@...il.com>
Cc: brauner@...nel.org, jack@...e.cz, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, skhan@...uxfoundation.org,
	david.hunter.linux@...il.com,
	linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] init: Use kcalloc() instead of kzalloc()

On Tue, Sep 30, 2025 at 09:35:37AM +0100, Mehdi Ben Hadj Khelifa wrote:
> Replace kzalloc() with kcalloc() in init/initramfs_test.c since the
> calculation inside kzalloc is dynamic and could overflow.

Really?  Could you explain how
	a) ARRAY_SIZE(local variable) * (CPIO_HDRLEN + PATH_MAX + 3)
could possibly be dynamic and
	b) just how large would that array have to be for it to "overflow"?

Incidentally, here the use of kcalloc would be unidiomatic - it's _not_
allocating an array of that many fixed-sized elements.  CPIO_HDRLEN +
PATH_MAX + 3 is not an element size - it's an upper bound on the amount
of space we might need for a single element.  Chunks of data generated
from array elements are placed into that buffer without any gaps -
it's really an array of bytes, large enough to fit all of them.