Commit a40ad41b authored Dec 08, 2023 by Heiko Carstens Committed by Greg Kroah-Hartman Jan 08, 2024

s390/vx: fix save/restore of fpu kernel context



[ 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: 7f79695c ("s390/fpu: improve kernel_fpu_[begin|end]")
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent d2939b19

arch/s390/include/asm/fpu/api.h

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -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_HIGH (KERNEL_VXR_V16V23\|KERNEL_VXR_V24V31)

	#define KERNEL_VXR (KERNEL_VXR_LOW\|KERNEL_VXR_HIGH)		#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;		struct kernel_fpu;