[PATCH 3.10 118/129] rbd: fix error handling from rbd_snap_name()

From: Greg Kroah-Hartman
Date: Mon Jan 06 2014 - 18:04:28 EST

3.10-stable review patch. If anyone has any objections, please let me know.


From: Josh Durgin <josh.durgin@xxxxxxxxxxx>

commit da6a6b63978d45f9ae582d1f362f182012da3a22 upstream.

rbd_snap_name() calls rbd_dev_v{1,2}_snap_name() depending on the
format of the image. The format 1 version returns NULL on error, which
is handled by the caller. The format 2 version returns an ERR_PTR,
which the caller of rbd_snap_name() does not expect.

Fortunately this is unlikely to occur in practice because
rbd_snap_id_by_name() is called before rbd_snap_name(). This would hit
similar errors to rbd_snap_name() (like the snapshot not existing) and
return early, so rbd_snap_name() would not hit an error unless the
snapshot was removed between the two calls or memory was exhausted.

Use an ERR_PTR in rbd_dev_v1_snap_name() so that the specific error
can be propagated, and it is consistent with rbd_dev_v2_snap_name().
Handle the ERR_PTR in the only rbd_snap_name() caller.

Suggested-by: Alex Elder <alex.elder@xxxxxxxxxx>
Signed-off-by: Josh Durgin <josh.durgin@xxxxxxxxxxx>
Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/block/rbd.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -937,12 +937,14 @@ static const char *rbd_dev_v1_snap_name(
u64 snap_id)
u32 which;
+ const char *snap_name;

which = rbd_dev_snap_index(rbd_dev, snap_id);
if (which == BAD_SNAP_INDEX)
- return NULL;
+ return ERR_PTR(-ENOENT);

- return _rbd_dev_v1_snap_name(rbd_dev, which);
+ snap_name = _rbd_dev_v1_snap_name(rbd_dev, which);
+ return snap_name ? snap_name : ERR_PTR(-ENOMEM);

static const char *rbd_snap_name(struct rbd_device *rbd_dev, u64 snap_id)
@@ -4140,8 +4142,8 @@ static int rbd_dev_spec_update(struct rb
/* Look up the snapshot name, and make a copy */

snap_name = rbd_snap_name(rbd_dev, spec->snap_id);
- if (!snap_name) {
- ret = -ENOMEM;
+ if (IS_ERR(snap_name)) {
+ ret = PTR_ERR(snap_name);
goto out_err;

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