linux-kernel - Re: [PATCH] libbpf: Fix integer overflow issue

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Message-ID: <20241007172248.GQ4017910@ZenIV>
Date: Mon, 7 Oct 2024 18:22:48 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: I Hsin Cheng <richard120310@...il.com>
Cc: martin.lau@...ux.dev, ast@...nel.org, daniel@...earbox.net,
	andrii@...nel.org, eddyz87@...il.com, song@...nel.org,
	yonghong.song@...ux.dev, john.fastabend@...il.com,
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com,
	jolsa@...nel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] libbpf: Fix integer overflow issue

On Tue, Oct 08, 2024 at 12:46:48AM +0800, I Hsin Cheng wrote:
> Fix integer overflow issue discovered by coverity scan, where
> "bpf_program_fd()" might return a value less than zero. Assignment of
> "prog_fd" to "kern_data" will result in integer overflow in that case.
> 
> Do a pre-check after the program fd is returned, if it's negative we
> should ignore this program and move on, or maybe add some error handling
> mechanism here.

We already had a mechanism there - the one you'd just disabled.
Namely, storing an unsigned long value with MSB set at given
offset.