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From:   Dan Clash <Dan.Clash@microsoft.com>
To:     Paul Moore <paul@paul-moore.com>, Jens Axboe <axboe@kernel.dk>
CC:     "audit@vger.kernel.org" <audit@vger.kernel.org>,
        "io-uring@vger.kernel.org" <io-uring@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "brauner@kernel.org" <brauner@kernel.org>
Subject: Re: [EXTERNAL] Re: audit: io_uring openat triggers audit reference
 count underflow in worker thread
Thread-Topic: [EXTERNAL] Re: audit: io_uring openat triggers audit reference
 count underflow in worker thread
Thread-Index: AQHZ+JAylfbNgEMpYU+qEdC5BlzyarA9m/2AgACyf4CAACH1gIACSc/N
Date:   Mon, 9 Oct 2023 02:38:43 +0000
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I retested with the following change as a sanity check:=0A=
=0A=
-       BUG_ON(name->refcnt <=3D 0);=0A=
+       BUG_ON(atomic_read(&name->refcnt) <=3D 0);=0A=
=0A=
checkpatch.pl suggests using WARN_ON_ONCE rather than BUG.=0A=
=0A=
devvm ~ $ ~/linux/scripts/checkpatch.pl --patch ~/io_uring_audit_hang_atomi=
c.patch =0A=
WARNING: Do not crash the kernel unless it is absolutely unavoidable=0A=
  --use WARN_ON_ONCE() plus recovery code (if feasible) instead of BUG() or=
 variants=0A=
#28: FILE: fs/namei.c:262:=0A=
+       BUG_ON(atomic_read(&name->refcnt) <=3D 0);=0A=
...=0A=
=0A=
refcount_t uses WARN_ON_ONCE.=0A=
=0A=
I can think of three choices:=0A=
=0A=
1. Use atomic_t and remove the BUG line.=0A=
2. Use refcount_t and remove the BUG line. =0A=
3. Use atomic_t and partially implement the warn behavior of refcount_t.=0A=
=0A=
Choice 1 and 2 seem better than choice 3.=0A=
=0A=
=0A=