nvmem: core: fix memory abort in cleanup path

nvmem_cell_info_to_nvmem_cell implementation has static
allocation of name. nvmem_add_cells_from_of() call may
return error and kfree name results in memory abort. Use
kstrdup_const() and kfree_const calls for name alloc and free.

Unable to handle kernel paging request at virtual address ffffffffffe44888
Mem abort info:
  ESR = 0x96000006
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
Data abort info:
  ISV = 0, ISS = 0x00000006
  CM = 0, WnR = 0
swapper pgtable: 64k pages, 48-bit VAs, pgdp=00000000815d0000
[ffffffffffe44888] pgd=0000000081d30803, pud=0000000081d30803,
pmd=0000000000000000
Internal error: Oops: 96000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 2 PID: 43 Comm: kworker/2:1 Tainted
Hardware name: quill (DT)
Workqueue: events deferred_probe_work_func
pstate: a0000005 (NzCv daif -PAN -UAO)
pc : kfree+0x38/0x278
lr : nvmem_cell_drop+0x68/0x80
sp : ffff80001284f9d0
x29: ffff80001284f9d0 x28: ffff0001f677e830
x27: ffff800011b0b000 x26: ffff0001c36e1008
x25: ffff8000112ad000 x24: ffff8000112c9000
x23: ffffffffffffffea x22: ffff800010adc7f0
x21: ffffffffffe44880 x20: ffff800011b0b068
x19: ffff80001122d380 x18: ffffffffffffffff
x17: 00000000d5cb4756 x16: 0000000070b193b8
x15: ffff8000119538c8 x14: 0720072007200720
x13: 07200720076e0772 x12: 07750762072d0765
x11: 0773077507660765 x10: 072f073007300730
x9 : 0730073207380733 x8 : 0000000000000151
x7 : 07660765072f0720 x6 : ffff0001c00e0f00
x5 : 0000000000000000 x4 : ffff0001c0b43800
x3 : ffff800011b0b068 x2 : 0000000000000000
x1 : 0000000000000000 x0 : ffffffdfffe00000
Call trace:
 kfree+0x38/0x278
 nvmem_cell_drop+0x68/0x80
 nvmem_device_remove_all_cells+0x2c/0x50
 nvmem_register.part.9+0x520/0x628
 devm_nvmem_register+0x48/0xa0
 tegra_fuse_probe+0x140/0x1f0
 platform_drv_probe+0x50/0xa0
 really_probe+0x108/0x348
 driver_probe_device+0x58/0x100
 __device_attach_driver+0x90/0xb0
 bus_for_each_drv+0x64/0xc8
 __device_attach+0xd8/0x138
 device_initial_probe+0x10/0x18
 bus_probe_device+0x90/0x98
 deferred_probe_work_func+0x74/0xb0
 process_one_work+0x1e0/0x358
 worker_thread+0x208/0x488
 kthread+0x118/0x120
 ret_from_fork+0x10/0x18
Code: d350feb5 f2dffbe0 aa1e03f6 8b151815 (f94006a0)
---[ end trace 49b1303c6b83198e ]---

Fixes: badcdff1 ("nvmem: Convert to using %pOFn instead of device_node.name")
Signed-off-by: Bitan Biswas <bbiswas@nvidia.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200109104017.6249-5-srinivas.kandagatla@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -83,7 +83,7 @@ static void nvmem_cell_drop(struct nvmem_cell *cell)
 	list_del(&cell->node);
 	mutex_unlock(&nvmem_mutex);
 	of_node_put(cell->np);
-	kfree(cell->name);
+	kfree_const(cell->name);
 	kfree(cell);
 }
 
@@ -110,7 +110,9 @@ static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
 	cell->nvmem = nvmem;
 	cell->offset = info->offset;
 	cell->bytes = info->bytes;
-	cell->name = info->name;
+	cell->name = kstrdup_const(info->name, GFP_KERNEL);
+	if (!cell->name)
+		return -ENOMEM;
 
 	cell->bit_offset = info->bit_offset;
 	cell->nbits = info->nbits;
@@ -300,7 +302,7 @@ static int nvmem_add_cells_from_of(struct nvmem_device *nvmem)
 			dev_err(dev, "cell %s unaligned to nvmem stride %d\n",
 				cell->name, nvmem->stride);
 			/* Cells already added will be freed later. */
-			kfree(cell->name);
+			kfree_const(cell->name);
 			kfree(cell);
 			return -EINVAL;
 		}