[PATCH v2] misc: sram: Fix NULL pointer dereference in sram_probe

[Andrey Tsygunka]

Add a check for the return value from platform_get_resource() call
to be NULL.

If the passed device-tree contains a node for sram-device
without a specified '<reg>' property value, for example:

    sram: sram@5c0000000 {
        compatible = "nvidia,tegra186-sysram";
    };

and the of_device_id[] '.data' element contains a sram_config*
with '.map_only_reserved = true' property, we get the error:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.1.96 #1
Hardware name: linux,dummy-virt (DT)
Call trace:
  sram_probe+0x134/0xd30
  platform_probe+0x94/0x130
  really_probe+0x124/0x580
  __driver_probe_device+0xd0/0x1f0
  driver_probe_device+0x50/0x1c0
  __device_attach_driver+0x140/0x220
  bus_for_each_drv+0xbc/0x130
  __device_attach+0xec/0x2c0
  device_initial_probe+0x24/0x40
  bus_probe_device+0xd8/0xe0
  device_add+0x67c/0xc80
  of_device_add+0x58/0x80
  of_platform_device_create_pdata+0xd0/0x1b0
  of_platform_bus_create+0x27c/0x6f0
  of_platform_populate+0xac/0x1d0
  of_platform_default_populate_init+0x10c/0x130
  do_one_initcall+0xdc/0x510
  kernel_init_freeable+0x43c/0x4d8
  kernel_init+0x2c/0x1e0
  ret_from_fork+0x10/0x20

Fixes: 444b0111f3bc ("misc: sram: use devm_platform_ioremap_resource_wc()")
Signed-off-by: Andrey Tsygunka <aitsygunka@xxxxxxxxx>
---
v2: Description changed based on comments from Markus Elfring 
at https://lore.kernel.org/linux-kernel/84969aba-67ba-4990-9065-6b55ce26ff92@xxxxxx/,
added tag 'Fixes', removed useless information from backtrace.

 drivers/misc/sram.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
index e5069882457e..c8ba8ebd4364 100644
--- a/drivers/misc/sram.c
+++ b/drivers/misc/sram.c
@@ -410,8 +410,13 @@ static int sram_probe(struct platform_device *pdev)
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
 
-	ret = sram_reserve_regions(sram,
-			platform_get_resource(pdev, IORESOURCE_MEM, 0));
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (unlikely(res == NULL)) {
+		dev_err(&pdev->dev, "invalid resource\n");
+		return -EINVAL;
+	}
+
+	ret = sram_reserve_regions(sram, res);
 	if (ret)
 		return ret;
 
-- 
2.25.1