Patch "s390/vx: fix save/restore of fpu kernel context" has been added to the 4.19-stable tree

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This is a note to let you know that I've just added the patch titled

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

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-vx-fix-save-restore-of-fpu-kernel-context.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2f746850fb93801721d44a9ec905ec019397d129
Author: Heiko Carstens <hca@xxxxxxxxxxxxx>
Date:   Fri Dec 8 15:03:15 2023 +0100

    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: 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>

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;
 




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