4.4-stable review patch. If anyone has any objections, please let me know.
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From: Martin Schwidefsky schwidefsky@de.ibm.com
From: Christian Borntraeger borntraeger@de.ibm.com
[ Upstream commit d3f468963cd6fd6d2aa5e26aed8b24232096d0e1 ]
when a system call is interrupted we might call the critical section cleanup handler that re-does some of the operations. When we are between .Lsysc_vtime and .Lsysc_do_svc we might also redo the saving of the problem state registers r0-r7:
.Lcleanup_system_call: [...] 0: # update accounting time stamp mvc __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER # set up saved register r11 lg %r15,__LC_KERNEL_STACK la %r9,STACK_FRAME_OVERHEAD(%r15) stg %r9,24(%r11) # r11 pt_regs pointer # fill pt_regs mvc __PT_R8(64,%r9),__LC_SAVE_AREA_SYNC ---> stmg %r0,%r7,__PT_R0(%r9)
The problem is now, that we might have already zeroed out r0. The fix is to move the zeroing of r0 after sysc_do_svc.
Reported-by: Farhan Ali alifm@linux.vnet.ibm.com Fixes: 7041d28115e91 ("s390: scrub registers on kernel entry and KVM exit") Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com
Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com
Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com
Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com
Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com
Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/kernel/entry.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -421,13 +421,13 @@ ENTRY(system_call) UPDATE_VTIME %r10,%r13,__LC_SYNC_ENTER_TIMER BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP stmg %r0,%r7,__PT_R0(%r11) - # clear user controlled register to prevent speculative use - xgr %r0,%r0 mvc __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC mvc __PT_PSW(16,%r11),__LC_SVC_OLD_PSW mvc __PT_INT_CODE(4,%r11),__LC_SVC_ILC stg %r14,__PT_FLAGS(%r11) .Lsysc_do_svc: + # clear user controlled register to prevent speculative use + xgr %r0,%r0 lg %r10,__TI_sysc_table(%r12) # address of system call table llgh %r8,__PT_INT_CODE+2(%r11) slag %r8,%r8,2 # shift and test for svc 0