Message-ID: <66b69a6fc5710_257529458@dwillia2-xfh.jf.intel.com.notmuch>
Date: Fri, 9 Aug 2024 15:38:39 -0700
From: Dan Williams <dan.j.williams@...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 v2 1/2] nvdimm: Fix devs leaks in scan_labels()

I notice this patch is not upstream yet. Let's try to get it over the
goal line.

Li Zhijian wrote:
> The leakage would happend when create_namespace_pmem() meets an invalid
> label which gets failure in validating isetcookie.

I would rewrite this as:

"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."

...then a distribution developer knows the urgency to backport this fix.

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

Rather than conditionally reallocating I think it would be better to
unconditionally allocate the minimum, something like:

diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index d6d558f94d6b..1c38c93bee21 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)) {
@@ -1994,10 +2000,6 @@ 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;
@@ -2036,12 +2038,10 @@ 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);
-       }
-       return NULL;
+        for (i = 0; devs[i]; i++)
+                namespace_pmem_release(devs[i]);
+        kfree(devs);
+        return NULL;
 }
 
 static struct device **create_namespaces(struct nd_region *nd_region)


> 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

Thanks for including this.

With the above changes you can add:

Reviewed-by: Dan Williams <dan.j.williams@...el.com>

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