[PATCH 3.19.y-ckt 133/196] s390/compat: correct restore of high gprs on signal return

From: Kamal Mostafa
Date: Tue Mar 08 2016 - 19:54:23 EST

3.19.8-ckt16 -stable review patch. If anyone has any objections, please let me know.


From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

commit 342300cc9cd3428bc6bfe5809bfcc1b9a0f06702 upstream.

git commit 8070361799ae1e3f4ef347bd10f0a508ac10acfb
"s390: add support for vector extension"
broke 31-bit compat processes in regard to signal handling.

The restore_sigregs_ext32() function is used to restore the additional
elements from the user space signal frame. Among the additional elements
are the upper registers halves for 64-bit register support for 31-bit
processes. The copy_from_user that is used to retrieve the high-gprs
array from the user stack uses an incorrect length, 8 bytes instead of
64 bytes. This causes incorrect upper register halves to get loaded.

Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
arch/s390/kernel/compat_signal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kernel/compat_signal.c b/arch/s390/kernel/compat_signal.c
index f564740..020e872 100644
--- a/arch/s390/kernel/compat_signal.c
+++ b/arch/s390/kernel/compat_signal.c
@@ -293,7 +293,7 @@ static int restore_sigregs_ext32(struct pt_regs *regs,

/* Restore high gprs from signal stack */
if (__copy_from_user(&gprs_high, &sregs_ext->gprs_high,
- sizeof(&sregs_ext->gprs_high)))
+ sizeof(sregs_ext->gprs_high)))
return -EFAULT;
for (i = 0; i < NUM_GPRS; i++)
*(__u32 *)&regs->gprs[i] = gprs_high[i];