[PATCH AUTOSEL 5.4 14/24] s390/ptrace: pass invalid syscall numbers to tracing

Sasha Levin
2020-06-23T17:39:59Z

From: Sven Schnelle <svens@linux.ibm.com>

[ Upstream commit 00332c16b1604242a56289ff2b26e283dbad0812 ]

tracing expects to see invalid syscalls, so pass it through.
The syscall path in entry.S checks the syscall number before
looking up the handler, so it is still safe.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/kernel/entry.S | 2 +-
arch/s390/kernel/ptrace.c | 6 ++----
2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index bc85987727f09..c544b7a11ebb3 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -368,9 +368,9 @@ ENTRY(system_call)
jnz .Lsysc_nr_ok
# svc 0: system call number in %r1
llgfr %r1,%r1 # clear high word in r1
+ sth %r1,__PT_INT_CODE+2(%r11)
cghi %r1,NR_syscalls
jnl .Lsysc_nr_ok
- sth %r1,__PT_INT_CODE+2(%r11)
slag %r8,%r1,3
.Lsysc_nr_ok:
xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index ad71132374f0c..5a2b1501d9983 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -844,11 +844,9 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
* call number to gprs[2].
*/
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- (tracehook_report_syscall_entry(regs) ||
- regs->gprs[2] >= NR_syscalls)) {
+ tracehook_report_syscall_entry(regs)) {
/*
- * Tracing decided this syscall should not happen or the
- * debugger stored an invalid system call number. Skip
+ * Tracing decided this syscall should not happen. Skip
* the system call and the system call restart handling.
*/
clear_pt_regs_flag(regs, PIF_SYSCALL);
--
2.25.1