linux-kernel - Re: [PATCH v3 1/2] nvdimm: Fix devs leaks in scan

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Message-ID: <66c6395260897_1719d294ec@iweiny-mobl.notmuch>
Date: Wed, 21 Aug 2024 14:00:34 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: Li Zhijian <lizhijian@...itsu.com>, <nvdimm@...ts.linux.dev>
CC: <dan.j.williams@...el.com>, <vishal.l.verma@...el.com>,
	<dave.jiang@...el.com>, <ira.weiny@...el.com>,
	<linux-kernel@...r.kernel.org>, Li Zhijian <lizhijian@...itsu.com>
Subject: Re: [PATCH v3 1/2] nvdimm: Fix devs leaks in scan_labels()

Li Zhijian wrote:
> scan_labels() leaks memory when label scanning fails and it falls back
> to just creating a default "seed" namespace for userspace to configure.
> Root can force the kernel to leak memory.
> 
> Allocate the minimum resources unconditionally and release them when
> unneeded to avoid the memory leak.
> 
> 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@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Fixes: 1b40e09a1232 ("libnvdimm: blk labels and namespace instantiation")
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>

Reviewed-by: Ira Weiny <ira.weiny@...el.com>


> ---
> V3:
>   update commit log and allocate the minimum(2 *dev) unconditionally. # Dan
> 
> V2:
>   update description and comment
> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
> ---
>  drivers/nvdimm/namespace_devs.c | 34 ++++++++++++++++-----------------
>  1 file changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
> index d6d558f94d6b..35d9f3cc2efa 100644
> --- a/drivers/nvdimm/namespace_devs.c
> +++ b/drivers/nvdimm/namespace_devs.c
> @@ -1937,12 +1937,16 @@ static int cmp_dpa(const void *a, const void *b)
>  static struct device **scan_labels(struct nd_region *nd_region)
>  {
>  	int i, count = 0;
> -	struct device *dev, **devs = NULL;
> +	struct device *dev, **devs;
>  	struct nd_label_ent *label_ent, *e;
>  	struct nd_mapping *nd_mapping = &nd_region->mapping[0];
>  	struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
>  	resource_size_t map_end = nd_mapping->start + nd_mapping->size - 1;
>  
> +	devs = kcalloc(2, sizeof(dev), GFP_KERNEL);
> +	if (!devs)
> +		return NULL;
> +
>  	/* "safe" because create_namespace_pmem() might list_move() label_ent */
>  	list_for_each_entry_safe(label_ent, e, &nd_mapping->labels, list) {
>  		struct nd_namespace_label *nd_label = label_ent->label;
> @@ -1961,12 +1965,14 @@ static struct device **scan_labels(struct nd_region *nd_region)
>  			goto err;
>  		if (i < count)
>  			continue;
> -		__devs = kcalloc(count + 2, sizeof(dev), GFP_KERNEL);
> -		if (!__devs)
> -			goto err;
> -		memcpy(__devs, devs, sizeof(dev) * count);
> -		kfree(devs);
> -		devs = __devs;
> +		if (count) {
> +			__devs = kcalloc(count + 2, sizeof(dev), GFP_KERNEL);
> +			if (!__devs)
> +				goto err;
> +			memcpy(__devs, devs, sizeof(dev) * count);
> +			kfree(devs);
> +			devs = __devs;
> +		}
>  
>  		dev = create_namespace_pmem(nd_region, nd_mapping, nd_label);
>  		if (IS_ERR(dev)) {
> @@ -1993,11 +1999,6 @@ 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);
> -		if (!devs)
> -			goto err;
> -
>  		nspm = kzalloc(sizeof(*nspm), GFP_KERNEL);
>  		if (!nspm)
>  			goto err;
> @@ -2036,11 +2037,10 @@ static struct device **scan_labels(struct nd_region *nd_region)
>  	return devs;
>  
>   err:
> -	if (devs) {
> -		for (i = 0; devs[i]; i++)
> -			namespace_pmem_release(devs[i]);
> -		kfree(devs);
> -	}
> +	for (i = 0; devs[i]; i++)
> +		namespace_pmem_release(devs[i]);
> +	kfree(devs);
> +
>  	return NULL;
>  }
>  
> -- 
> 2.29.2
>