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Tue, 01 Oct 2024 07:58:36 -0700 (PDT) Date: Tue, 01 Oct 2024 07:58:36 -0700 In-Reply-To: <00000000000061641905cbd98d7b@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <66fc0e1c.050a0220.f28ec.04aa.GAE@google.com> Subject: Re: [syzbot] Re: [PATCH v1] Bluetooth: RFCOMM: FIX possible deadlock in rfcomm_sk_state_change From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: Re: [PATCH v1] Bluetooth: RFCOMM: FIX possible deadlock in rfcomm_= sk_state_change Author: luiz.dentz@gmail.com #syz test On Mon, Sep 30, 2024 at 4:36=E2=80=AFPM Luiz Augusto von Dentz wrote: > > On Mon, Sep 30, 2024 at 3:30=E2=80=AFPM Luiz Augusto von Dentz > wrote: > > > > From: Luiz Augusto von Dentz > > > > rfcomm_sk_state_change attempts to use sock_lock so it must never be > > called with it locked but rfcomm_sock_ioctl always attempt to lock it > > causing the following trace: > > > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D > > WARNING: possible circular locking dependency detected > > 6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted > > ------------------------------------------------------ > > syz-executor386/5093 is trying to acquire lock: > > ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at:= lock_sock include/net/sock.h:1671 [inline] > > ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at:= rfcomm_sk_state_change+0x5b/0x310 net/bluetooth/rfcomm/sock.c:73 > > > > but task is already holding lock: > > ffff88807badfd28 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x226/0= x6a0 net/bluetooth/rfcomm/core.c:491 > > > > Reported-by: syzbot+d7ce59b06b3eb14fd218@syzkaller.appspotmail.com > > Closes: https://syzkaller.appspot.com/bug?extid=3Dd7ce59b06b3eb14fd218 > > Fixes: 3241ad820dbb ("[Bluetooth] Add timestamp support to L2CAP, RFCOM= M and SCO") > > Signed-off-by: Luiz Augusto von Dentz > > --- > > net/bluetooth/rfcomm/sock.c | 2 -- > > 1 file changed, 2 deletions(-) > > > > diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c > > index 37d63d768afb..f48250e3f2e1 100644 > > --- a/net/bluetooth/rfcomm/sock.c > > +++ b/net/bluetooth/rfcomm/sock.c > > @@ -865,9 +865,7 @@ static int rfcomm_sock_ioctl(struct socket *sock, u= nsigned int cmd, unsigned lon > > > > if (err =3D=3D -ENOIOCTLCMD) { > > #ifdef CONFIG_BT_RFCOMM_TTY > > - lock_sock(sk); > > err =3D rfcomm_dev_ioctl(sk, cmd, (void __user *) arg); > > - release_sock(sk); > > #else > > err =3D -EOPNOTSUPP; > > #endif > > -- > > 2.46.1 > > > > > -- > Luiz Augusto von Dentz --=20 Luiz Augusto von Dentz