mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-10-14 12:37:32 +00:00
Code Issues Releases Wiki Activity

s390/entry.S: fix spurious zeroing of r0

Browse source 
[ Upstream commit d3f468963c ]

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: 7041d28115 ("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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christian Borntraeger 2018-04-27 07:36:37 +02:00 committed by Greg Kroah-Hartman
parent 74a93ae5c3
commit 6cdc4b21d2
1 changed files with 2 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
arch/s390/kernel/entry.S
View file

@ -426,13 +426,13 @@ ENTRY(system_call)
UPDATE_VTIME %r8,%r9,__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
# load address of system call table
lg %r10,__THREAD_sysc_table(%r13,%r12)
llgh %r8,__PT_INT_CODE+2(%r11)