[PATCH 3.16 081/328] partitions/aix: fix usage of uninitialized lv_info and lvname structures

[Ben Hutchings]

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mauricio Faria de Oliveira <mfo@xxxxxxxxxxxxx>

commit 14cb2c8a6c5dae57ee3e2da10fa3db2b9087e39e upstream.

The if-block that sets a successful return value in aix_partition()
uses 'lvip[].pps_per_lv' and 'n[].name' potentially uninitialized.

For example, if 'numlvs' is zero or alloc_lvn() fails, neither is
initialized, but are used anyway if alloc_pvd() succeeds after it.

So, make the alloc_pvd() call conditional on their initialization.

This has been hit when attaching an apparently corrupted/stressed
AIX LUN, misleading the kernel to pr_warn() invalid data and hang.

    [...] partition (null) (11 pp's found) is not contiguous
    [...] partition (null) (2 pp's found) is not contiguous
    [...] partition (null) (3 pp's found) is not contiguous
    [...] partition (null) (64 pp's found) is not contiguous

Fixes: 6ceea22bbbc8 ("partitions: add aix lvm partition support files")
Signed-off-by: Mauricio Faria de Oliveira <mfo@xxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 block/partitions/aix.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/block/partitions/aix.c
+++ b/block/partitions/aix.c
@@ -177,7 +177,7 @@ int aix_partition(struct parsed_partitio
 	u32 vgda_sector = 0;
 	u32 vgda_len = 0;
 	int numlvs = 0;
-	struct pvd *pvd;
+	struct pvd *pvd = NULL;
 	struct lv_info {
 		unsigned short pps_per_lv;
 		unsigned short pps_found;
@@ -231,10 +231,11 @@ int aix_partition(struct parsed_partitio
 				if (lvip[i].pps_per_lv)
 					foundlvs += 1;
 			}
+			/* pvd loops depend on n[].name and lvip[].pps_per_lv */
+			pvd = alloc_pvd(state, vgda_sector + 17);
 		}
 		put_dev_sector(sect);
 	}
-	pvd = alloc_pvd(state, vgda_sector + 17);
 	if (pvd) {
 		int numpps = be16_to_cpu(pvd->pp_count);
 		int psn_part1 = be32_to_cpu(pvd->psn_part1);