[tip:x86/boot] x86/corruption-check: Fix panic in memory_corruption_check() when boot option without value is provided

[tip-bot for He Zhe]

Commit-ID:  ccde460b9ae5c2bd5e4742af0a7f623c2daad566
Gitweb:     https://git.kernel.org/tip/ccde460b9ae5c2bd5e4742af0a7f623c2daad566
Author:     He Zhe <zhe.he@xxxxxxxxxxxxx>
AuthorDate: Tue, 14 Aug 2018 23:33:42 +0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 10 Sep 2018 14:47:32 +0200

x86/corruption-check: Fix panic in memory_corruption_check() when boot option without value is provided

memory_corruption_check[{_period|_size}]()'s handlers do not check input
argument before passing it to kstrtoul() or simple_strtoull(). The argument
would be a NULL pointer if each of the kernel parameters, without its
value, is set in command line and thus cause the following panic.

PANIC: early exception 0xe3 IP 10:ffffffff73587c22 error 0 cr2 0x0
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.18-rc8+ #2
[    0.000000] RIP: 0010:kstrtoull+0x2/0x10
...
[    0.000000] Call Trace
[    0.000000]  ? set_corruption_check+0x21/0x49
[    0.000000]  ? do_early_param+0x4d/0x82
[    0.000000]  ? parse_args+0x212/0x330
[    0.000000]  ? rdinit_setup+0x26/0x26
[    0.000000]  ? parse_early_options+0x20/0x23
[    0.000000]  ? rdinit_setup+0x26/0x26
[    0.000000]  ? parse_early_param+0x2d/0x39
[    0.000000]  ? setup_arch+0x2f7/0xbf4
[    0.000000]  ? start_kernel+0x5e/0x4c2
[    0.000000]  ? load_ucode_bsp+0x113/0x12f
[    0.000000]  ? secondary_startup_64+0xa5/0xb0

This patch adds checks to prevent the panic.

Signed-off-by: He Zhe <zhe.he@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: kstewart@xxxxxxxxxxxxxxxxxxx
Cc: pombredanne@xxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1534260823-87917-1-git-send-email-zhe.he@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/check.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/x86/kernel/check.c b/arch/x86/kernel/check.c
index 33399426793e..cc8258a5378b 100644
--- a/arch/x86/kernel/check.c
+++ b/arch/x86/kernel/check.c
@@ -31,6 +31,11 @@ static __init int set_corruption_check(char *arg)
 	ssize_t ret;
 	unsigned long val;
 
+	if (!arg) {
+		pr_err("memory_corruption_check config string not provided\n");
+		return -EINVAL;
+	}
+
 	ret = kstrtoul(arg, 10, &val);
 	if (ret)
 		return ret;
@@ -45,6 +50,11 @@ static __init int set_corruption_check_period(char *arg)
 	ssize_t ret;
 	unsigned long val;
 
+	if (!arg) {
+		pr_err("memory_corruption_check_period config string not provided\n");
+		return -EINVAL;
+	}
+
 	ret = kstrtoul(arg, 10, &val);
 	if (ret)
 		return ret;
@@ -59,6 +69,11 @@ static __init int set_corruption_check_size(char *arg)
 	char *end;
 	unsigned size;
 
+	if (!arg) {
+		pr_err("memory_corruption_check_size config string not provided\n");
+		return -EINVAL;
+	}
+
 	size = memparse(arg, &end);
 
 	if (*end == '\0')