[net] ptp: fix NULL pointer dereference in ptp_clock_register

Fix NULL pointer dereference in ptp_clock_register. The argument
"parent" of ptp_clock_register may be NULL pointer.

Fixes: 73f37068d540 ("ptp: support ptp physical/virtual clocks conversion")
Reported-by: kernel test robot <redacted>
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
---
 drivers/ptp/ptp_clock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index f012fa581cf4..ce6d9fc85607 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c

@@ -236,7 +236,7 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	}
 
 	/* PTP virtual clock is being registered under physical clock */
-	if (parent->class && parent->class->name &&
+	if (parent && parent->class && parent->class->name &&
 	    strcmp(parent->class->name, "ptp") == 0)
 		ptp->is_virtual_clock = true;
 

base-commit: 6ff63a150b5556012589ae59efac1b5eeb7d32c3
-- 
2.25.1

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Mon,  5 Jul 2021 16:53:06 +0800 you wrote:

Fix NULL pointer dereference in ptp_clock_register. The argument
"parent" of ptp_clock_register may be NULL pointer.

Fixes: 73f37068d540 ("ptp: support ptp physical/virtual clocks conversion")
Reported-by: kernel test robot <redacted>
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>

[...]

Here is the summary with links:
  - [net] ptp: fix NULL pointer dereference in ptp_clock_register
    https://git.kernel.org/netdev/net/c/55eac20617ca

You are awesome, thank you!
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