linux-kernel - Re: [PATCH] hwrng: core - fix task hung in hwrng

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Message-ID: <ZWpukgSDlA6UFR6e@gondor.apana.org.au>
Date:   Sat, 2 Dec 2023 07:38:58 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Edward Adam Davis <eadavis@...com>
Cc:     davem@...emloft.net, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, olivia@...enic.com,
        syzbot+c52ab18308964d248092@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] hwrng: core - fix task hung in hwrng_fillfn

On Fri, Dec 01, 2023 at 08:34:12PM +0800, Edward Adam Davis wrote:
>
> According to splat, after a page fault occurred, the attempt to retrieve 
> rcu_read_lock() failed, resulting in a timeout of 143s. This is my speculation.

Oh I see what's going on.  The reproducer is mapping /dev/hwrng, so
the write to user-space is then triggering another read which then
dead-locks.

Let me think about this.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt