5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Heiko Carstens <hca@xxxxxxxxxxxxx>
[ Upstream commit e6b2dab41888332bf83f592131e7ea07756770a4 ]
The KERNEL_FPR mask only contains a flag for the first eight vector
registers. However floating point registers overlay parts of the first
sixteen vector registers.
This could lead to vector register corruption if a kernel fpu context uses
any of the vector registers 8 to 15 and is interrupted or calls a
KERNEL_FPR context. If that context uses also vector registers 8 to 15,
their contents will be corrupted on return.
Luckily this is currently not a real bug, since the kernel has only one
KERNEL_FPR user with s390_adjust_jiffies() and it is only using floating
point registers 0 to 2.
Fix this by using the correct bits for KERNEL_FPR.
Fixes: 7f79695cc1b6 ("s390/fpu: improve kernel_fpu_[begin|end]")
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Reviewed-by: Hendrik Brueckner <brueckner@xxxxxxxxxxxxx>
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/s390/include/asm/fpu/api.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/s390/include/asm/fpu/api.h b/arch/s390/include/asm/fpu/api.h
index 34a7ae68485c6..be16a6c0f1276 100644
--- a/arch/s390/include/asm/fpu/api.h
+++ b/arch/s390/include/asm/fpu/api.h
@@ -76,7 +76,7 @@ static inline int test_fp_ctl(u32 fpc)
#define KERNEL_VXR_HIGH (KERNEL_VXR_V16V23|KERNEL_VXR_V24V31)
#define KERNEL_VXR (KERNEL_VXR_LOW|KERNEL_VXR_HIGH)
-#define KERNEL_FPR (KERNEL_FPC|KERNEL_VXR_V0V7)
+#define KERNEL_FPR (KERNEL_FPC|KERNEL_VXR_LOW)
struct kernel_fpu;
--
2.43.0
