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

[Ira Weiny]

Li Zhijian wrote:
> 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")

What is the bigger effect the user will see?

Does this cause a long term user effect?  For example, if a users system
has a bad label I think this is going to be a pretty minor memory leak
which just hangs around until reboot, correct?

> 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.

NP, sometimes it takes a while to really debug something.

> 
> 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);

I'm still tempted to try and fix the count but I think this will work.
Let me know about the severity of the issue.

Ira

>  		if (!devs)
>  			goto err;
>  
> -- 
> 2.29.2
>