[PATCH v2 1/2] nvdimm: Fix devs leaks in scan_labels()

[Li Zhijian]

The leakage would happend when create_namespace_pmem() meets an invalid
label which gets failure in validating isetcookie.

Try to resuse the devs that may have already been allocated with size
(2 * sizeof(dev)) previously.

A kmemleak reports:
unreferenced object 0xffff88800dda1980 (size 16):
  comm "kworker/u10:5", pid 69, jiffies 4294671781
  hex dump (first 16 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    [<00000000c5dea560>] __kmalloc+0x32c/0x470
    [<000000009ed43c83>] nd_region_register_namespaces+0x6fb/0x1120 [libnvdimm]
    [<000000000e07a65c>] nd_region_probe+0xfe/0x210 [libnvdimm]
    [<000000007b79ce5f>] nvdimm_bus_probe+0x7a/0x1e0 [libnvdimm]
    [<00000000a5f3da2e>] really_probe+0xc6/0x390
    [<00000000129e2a69>] __driver_probe_device+0x78/0x150
    [<000000002dfed28b>] driver_probe_device+0x1e/0x90
    [<00000000e7048de2>] __device_attach_driver+0x85/0x110
    [<0000000032dca295>] bus_for_each_drv+0x85/0xe0
    [<00000000391c5a7d>] __device_attach+0xbe/0x1e0
    [<0000000026dabec0>] bus_probe_device+0x94/0xb0
    [<00000000c590d936>] device_add+0x656/0x870
    [<000000003d69bfaa>] nd_async_device_register+0xe/0x50 [libnvdimm]
    [<000000003f4c52a4>] async_run_entry_fn+0x2e/0x110
    [<00000000e201f4b0>] process_one_work+0x1ee/0x600
    [<000000006d90d5a9>] worker_thread+0x183/0x350

Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Fixes: 1b40e09a1232 ("libnvdimm: blk labels and namespace instantiation")
Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
---

Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> From what I can tell create_namespace_pmem() must be returning EAGAIN
> which leaves devs allocated but fails to increment count.  Thus there are
> no valid labels but devs was not free'ed.

> Can you trace the error you are seeing a bit more to see if this is the
> case?
  Hi Ira, Sorry for the late reply. I have reproduced it these days.
  Yeah, the LSA is containing a label in which the isetcookie is invalid.

V2:
  update description and comment
---
 drivers/nvdimm/namespace_devs.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index d6d558f94d6b..28c9afc01dca 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -1994,7 +1994,13 @@ static struct device **scan_labels(struct nd_region *nd_region)
 		/* Publish a zero-sized namespace for userspace to configure. */
 		nd_mapping_free_labels(nd_mapping);
 
-		devs = kcalloc(2, sizeof(dev), GFP_KERNEL);
+		/*
+		 * Try to use the devs that may have already been allocated
+		 * above first. This would happend when create_namespace_pmem()
+		 * meets an invalid label.
+		 */
+		if (!devs)
+			devs = kcalloc(2, sizeof(dev), GFP_KERNEL);
 		if (!devs)
 			goto err;
 
-- 
2.29.2