[tip:x86/urgent] x86/hpet: Prevent potential NULL pointer dereference

[tip-bot for Aditya Pakki <tipbot@zytor.com>]

Commit-ID:  2e84f116afca3719c9d0a1a78b47b48f75fd5724
Gitweb:     https://git.kernel.org/tip/2e84f116afca3719c9d0a1a78b47b48f75fd5724
Author:     Aditya Pakki <pakki001@umn.edu>
AuthorDate: Mon, 18 Mar 2019 21:19:56 -0500
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 21 Mar 2019 12:24:38 +0100

x86/hpet: Prevent potential NULL pointer dereference

hpet_virt_address may be NULL when ioremap_nocache fail, but the code lacks
a check.

Add a check to prevent NULL pointer dereference.

Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: kjlu@umn.edu
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Joe Perches <joe@perches.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Roland Dreier <roland@purestorage.com>
Link: https://lkml.kernel.org/r/20190319021958.17275-1-pakki001@umn.edu

---
 arch/x86/kernel/hpet.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index dfd3aca82c61..fb32925a2e62 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -905,6 +905,8 @@ int __init hpet_enable(void)
 		return 0;
 
 	hpet_set_mapping();
+	if (!hpet_virt_address)
+		return 0;
 
 	/*
 	 * Read the period and check for a sane value: