diff mbox series

x86/xen: Remove undefined behavior in setup_features()

Message ID 20220617103037.57828-1-julien@xen.org (mailing list archive)
State Accepted
Commit ecb6237fa397b7b810d798ad19322eca466dbab1
Headers show
Series x86/xen: Remove undefined behavior in setup_features() | expand

Commit Message

Julien Grall June 17, 2022, 10:30 a.m. UTC 
From: Julien Grall <jgrall@amazon.com>

1 << 31 is undefined. So switch to 1U << 31.

Fixes: 5ead97c84fa7 ("xen: Core Xen implementation")
Signed-off-by: Julien Grall <jgrall@amazon.com>

---

This was actually caught because I wasn't able to boot Linux 5.18
and onwards when built with GCC 7.3 and UBSAN enabled. There was
no message but instead an early crash because the instruction "cli
was used too early.

This issue has always been there but it only shows after Linux
switched from C89 to C11.
---
 drivers/xen/features.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Jürgen Groß June 17, 2022, 10:32 a.m. UTC | #1 
On 17.06.22 12:30, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> 1 << 31 is undefined. So switch to 1U << 31.
> 
> Fixes: 5ead97c84fa7 ("xen: Core Xen implementation")
> Signed-off-by: Julien Grall <jgrall@amazon.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen
Jürgen Groß June 23, 2022, 1 p.m. UTC | #2 
On 17.06.22 12:30, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> 1 << 31 is undefined. So switch to 1U << 31.
> 
> Fixes: 5ead97c84fa7 ("xen: Core Xen implementation")
> Signed-off-by: Julien Grall <jgrall@amazon.com>

Pushed to xen/tip.git for-linus-5.19a


Juergen
diff mbox series

Patch

diff --git a/drivers/xen/features.c b/drivers/xen/features.c
index 7b591443833c..87f1828d40d5 100644
--- a/drivers/xen/features.c
+++ b/drivers/xen/features.c
@@ -42,7 +42,7 @@  void xen_setup_features(void)
 		if (HYPERVISOR_xen_version(XENVER_get_features, &fi) < 0)
 			break;
 		for (j = 0; j < 32; j++)
-			xen_features[i * 32 + j] = !!(fi.submap & 1<<j);
+			xen_features[i * 32 + j] = !!(fi.submap & 1U << j);
 	}
 
 	if (xen_pv_domain()) {