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Subject: Re: [PATCH] afs: Fix missing/incorrect unlocking of RCU read lock
From: Alan Huang <mmpgouride@gmail.com>
In-Reply-To: <2929034.1705508082@warthog.procyon.org.uk>
Date: Thu, 18 Jan 2024 01:15:02 +0800
Cc: Marc Dionne <marc.dionne@auristor.com>,
 linux-afs@lists.infradead.org,
 linux-fsdevel@vger.kernel.org,
 linux-kernel@vger.kernel.org
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Message-Id: <D21C0923-8182-43A4-A3D0-0DB9DC07F638@gmail.com>
References: <2929034.1705508082@warthog.procyon.org.uk>
To: David Howells <dhowells@redhat.com>


> 2024=E5=B9=B41=E6=9C=8818=E6=97=A5 00:14=EF=BC=8CDavid Howells =
<dhowells@redhat.com> =E5=86=99=E9=81=93=EF=BC=9A
>=20
> In afs_proc_addr_prefs_show(), we need to unlock the RCU read lock in =
both
> places before returning (and not lock it again).
>=20
> Fixes: f94f70d39cc2 ("afs: Provide a way to configure address =
priorities")
> Reported-by: Marc Dionne <marc.dionne@auristor.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: linux-afs@lists.infradead.org
> cc: linux-fsdevel@vger.kernel.org
> ---
> fs/afs/proc.c |    5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>=20
> diff --git a/fs/afs/proc.c b/fs/afs/proc.c
> index 3bd02571f30d..15eab053af6d 100644
> --- a/fs/afs/proc.c
> +++ b/fs/afs/proc.c
> @@ -166,7 +166,7 @@ static int afs_proc_addr_prefs_show(struct =
seq_file *m, void *v)
>=20
> if (!preflist) {
> seq_puts(m, "NO PREFS\n");
> - return 0;
> + goto out;
> }
>=20
> seq_printf(m, "PROT SUBNET                                      PRIOR =
(v=3D%u n=3D%u/%u/%u)\n",
> @@ -191,7 +191,8 @@ static int afs_proc_addr_prefs_show(struct =
seq_file *m, void *v)
> }
> }
>=20
> - rcu_read_lock();
> +out:
> + rcu_read_unlock();

What about using:

	guard(rcu)();

Thanks,
Alan

> return 0;
> }
>=20
>=20