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Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Tue, 26 Jul 2022 11:35:19 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Yury Norov <yury.norov@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Dennis Zhou <dennis@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm: drop arch implementation for find_bit() functions
Message-ID: <20220726183519.GA931941@roeck-us.net>
References: <20220726154407.3464776-1-yury.norov@gmail.com>
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On Tue, Jul 26, 2022 at 08:44:07AM -0700, Yury Norov wrote:
> find_next_bit(bitmap, nbits, off) shouldn't touch memory if
> nbits == 0 or off >= nbits to avoid out-of-boundary access.
> 
> Generic implementation has explicit check for this, but arm doesn't,
> which is spotted by KFENCE when running test_bitmap.
> 
...
> CC: Guenter Roeck <linux@roeck-us.net>
> CC: Dennis Zhou <dennis@kernel.org>
> CC: Russell King <linux@armlinux.org.uk>
> CC: Catalin Marinas <catalin.marinas@arm.com>
> CC: linux-arm-kernel@lists.infradead.org
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>

bitmap unit tests succeed, and the KFENCE report is no longer seen
even after 65 retries (previously it reproduced easily with 5-15
retries).

Tested-by: Guenter Roeck <linux@roeck-us.net>

Guenter