diff mbox series

[v3,24/34] s390/cpumf: Unpoison STCCTM output buffer

Message ID 20231213233605.661251-25-iii@linux.ibm.com
State New
Headers
Series kmsan: Enable on s390 |

Commit Message

Ilya Leoshkevich Dec. 13, 2023, 11:24 p.m. UTC 
  stcctm() uses the "Q" constraint for dest, therefore KMSAN does not
understand that it fills multiple doublewords pointed to by dest, not
just one. This results in false positives.

Unpoison the whole dest manually with kmsan_unpoison_memory().

Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/include/asm/cpu_mf.h | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Alexander Potapenko Dec. 20, 2023, 11:04 a.m. UTC | #1 
On Thu, Dec 14, 2023 at 12:37 AM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>
> stcctm() uses the "Q" constraint for dest, therefore KMSAN does not
> understand that it fills multiple doublewords pointed to by dest, not
> just one. This results in false positives.
>
> Unpoison the whole dest manually with kmsan_unpoison_memory().
>
> Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Heiko Carstens Jan. 2, 2024, 2:38 p.m. UTC | #2 
On Thu, Dec 14, 2023 at 12:24:44AM +0100, Ilya Leoshkevich wrote:
> stcctm() uses the "Q" constraint for dest, therefore KMSAN does not
> understand that it fills multiple doublewords pointed to by dest, not
> just one. This results in false positives.
> 
> Unpoison the whole dest manually with kmsan_unpoison_memory().
> 
> Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  arch/s390/include/asm/cpu_mf.h | 6 ++++++
>  1 file changed, 6 insertions(+)

Acked-by: Heiko Carstens <hca@linux.ibm.com>
diff mbox series

Patch

diff --git a/arch/s390/include/asm/cpu_mf.h b/arch/s390/include/asm/cpu_mf.h
index a0de5b9b02ea..9e4bbc3e53f8 100644
--- a/arch/s390/include/asm/cpu_mf.h
+++ b/arch/s390/include/asm/cpu_mf.h
@@ -10,6 +10,7 @@ 
 #define _ASM_S390_CPU_MF_H
 
 #include <linux/errno.h>
+#include <linux/kmsan-checks.h>
 #include <asm/asm-extable.h>
 #include <asm/facility.h>
 
@@ -239,6 +240,11 @@  static __always_inline int stcctm(enum stcctm_ctr_set set, u64 range, u64 *dest)
 		: "=d" (cc)
 		: "Q" (*dest), "d" (range), "i" (set)
 		: "cc", "memory");
+	/*
+	 * If cc == 2, less than RANGE counters are stored, but it's not easy
+	 * to tell how many. Always unpoison the whole range for simplicity.
+	 */
+	kmsan_unpoison_memory(dest, range * sizeof(u64));
 	return cc;
 }