kern/162036: [geom] Fatal trap 12: page fault while in kernel mode -- Stopped at atomic_subtract_int+0x4

[Fabian Keil]

The following reply was made to PR kern/162036; it has been noted by GNATS.

From: Fabian Keil <fk at fabiankeil.de>
To: bug-followup at FreeBSD.org
Cc:  
Subject: kern/162036: [geom] Fatal trap 12: page fault while in kernel mode
 -- Stopped at atomic_subtract_int+0x4
Date: Fri, 22 Feb 2013 17:59:13 +0100

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 The problem still exists with a current kernel but apparently
 the atomic_subtract_int() call has been relocated.
 
 As the result there are now two related panics caused by
 g_eli_read_done() and (sometimes) g_eli_crypto_read_done()
 being called with:
 
 (kgdb) p bp->bio_parent->bio_to->geom->softc
 $1 =3D (void *) 0x0
 
 The attached patch adds the missing pointer checks and seems
 to prevent the panics for me.
 
 So far I haven't seen similar panics in the g_*_write_done()
 functions, although they look rather similar.
 
 Fabian
 
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  filename=kern-162036-Let-g_eli_-read_done-deal-with-lost-devices.patch
 
 =46rom 52a4fac396eaaaadd7a79a0d4311f38bdc3d3141 Mon Sep 17 00:00:00 2001
 From: Fabian Keil <fk at fabiankeil.de>
 Date: Tue, 19 Feb 2013 14:42:00 +0100
 Subject: [PATCH 1/2] Let g_eli_*read_done() deal with lost devices without
  causing panics
 
 Seems to fix kern/162036 for me.
 ---
  sys/geom/eli/g_eli.c         | 3 ++-
  sys/geom/eli/g_eli_privacy.c | 6 ++++--
  2 files changed, 6 insertions(+), 3 deletions(-)
 
 diff --git a/sys/geom/eli/g_eli.c b/sys/geom/eli/g_eli.c
 index 4e35297..24969b0 100644
 --- a/sys/geom/eli/g_eli.c
 +++ b/sys/geom/eli/g_eli.c
 @@ -183,7 +183,8 @@ g_eli_read_done(struct bio *bp)
  			pbp->bio_driver2 =3D NULL;
  		}
  		g_io_deliver(pbp, pbp->bio_error);
 -		atomic_subtract_int(&sc->sc_inflight, 1);
 +		if (sc !=3D NULL)
 +			atomic_subtract_int(&sc->sc_inflight, 1);
  		return;
  	}
  	mtx_lock(&sc->sc_queue_mtx);
 diff --git a/sys/geom/eli/g_eli_privacy.c b/sys/geom/eli/g_eli_privacy.c
 index f353832..938883a 100644
 --- a/sys/geom/eli/g_eli_privacy.c
 +++ b/sys/geom/eli/g_eli_privacy.c
 @@ -88,7 +88,8 @@ g_eli_crypto_read_done(struct cryptop *crp)
  			bp->bio_error =3D crp->crp_etype;
  	}
  	sc =3D bp->bio_to->geom->softc;
 -	g_eli_key_drop(sc, crp->crp_desc->crd_key);
 +	if (sc !=3D NULL)
 +		g_eli_key_drop(sc, crp->crp_desc->crd_key);
  	/*
  	 * Do we have all sectors already?
  	 */
 @@ -105,7 +106,8 @@ g_eli_crypto_read_done(struct cryptop *crp)
  	 * Read is finished, send it up.
  	 */
  	g_io_deliver(bp, bp->bio_error);
 -	atomic_subtract_int(&sc->sc_inflight, 1);
 +	if (sc !=3D NULL)
 +		atomic_subtract_int(&sc->sc_inflight, 1);
  	return (0);
  }
 =20
 --=20
 1.8.1.3
 
 
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