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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: 7f79695cc1 ("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>
This commit is contained in:
Heiko Carstens 2023-12-08 15:03:15 +01:00 committed by Greg Kroah-Hartman
parent 11dfea080f
commit 602490b469
1 changed files with 1 additions and 1 deletions
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2
arch/s390/include/asm/fpu/api.h
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@ -79,7 +79,7 @@ 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;