From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
commit 50e43a57334400668952f8e551c9d87d3ed2dfef upstream.
We get there when sigreturn has performed obscene acts on kernel stack;
in particular, the location of pt_regs has shifted. We are about to call
syscall_trace(), which might stop for tracer. If that happens, we'd better
have task_pt_regs() returning correct result...
Fucked-up-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Fixes: bd6f56a75bb2 ("m68k: Missing syscall_trace() on sigreturn")
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Tested-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Reviewed-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Tested-by: Finn Thain <fthain@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/YP2dMWeV1LkHiOpr@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: <cip-dev@xxxxxxxxxxxxxxxxxxxxx> # 4.4
Signed-off-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
---
arch/m68k/kernel/entry.S | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
index b54ac7aba850..dbeba043b703 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -173,6 +173,8 @@ ENTRY(ret_from_signal)
movel %curptr@(TASK_STACK),%a1
tstb %a1@(TINFO_FLAGS+2)
jge 1f
+ lea %sp@(SWITCH_STACK_SIZE),%a1
+ movel %a1,%curptr@(TASK_THREAD+THREAD_ESP0)
jbsr syscall_trace
1: RESTORE_SWITCH_STACK
addql #4,%sp
--
2.17.1
