[PATCH 5.7 195/265] s390/ptrace: return -ENOSYS when invalid syscall is supplied

[Sasha Levin]

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

[ Upstream commit cd29fa798001075a554b978df3a64e6656c25794 ]

The current code returns the syscall number which an invalid
syscall number is supplied and tracing is enabled. This makes
the strace testsuite fail.

Signed-off-by: Sven Schnelle <sv...@linux.ibm.com>
Signed-off-by: Vasily Gorbik <g...@linux.ibm.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 arch/s390/kernel/ptrace.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 9eee345568890..3f29646313e82 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -838,6 +838,7 @@ long compat_arch_ptrace(struct task_struct *child, 
compat_long_t request,
 asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 {
        unsigned long mask = -1UL;
+       long ret = -1;
 
        if (is_compat_task())
                mask = 0xffffffff;
@@ -854,8 +855,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
                 * debugger stored an invalid system call number. Skip
                 * the system call and the system call restart handling.
                 */
-               clear_pt_regs_flag(regs, PIF_SYSCALL);
-               return -1;
+               goto skip;
        }
 
 #ifdef CONFIG_SECCOMP
@@ -871,7 +871,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
                        sd.arch = AUDIT_ARCH_S390X;
                }
 
-               sd.nr = regs->gprs[2] & 0xffff;
+               sd.nr = regs->int_code & 0xffff;
                sd.args[0] = regs->orig_gpr2 & mask;
                sd.args[1] = regs->gprs[3] & mask;
                sd.args[2] = regs->gprs[4] & mask;
@@ -880,19 +880,26 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs 
*regs)
                sd.args[5] = regs->gprs[7] & mask;
 
                if (__secure_computing(&sd) == -1)
-                       return -1;
+                       goto skip;
        }
 #endif /* CONFIG_SECCOMP */
 
        if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
-               trace_sys_enter(regs, regs->gprs[2]);
+               trace_sys_enter(regs, regs->int_code & 0xffff);
 
 
-       audit_syscall_entry(regs->gprs[2], regs->orig_gpr2 & mask,
+       audit_syscall_entry(regs->int_code & 0xffff, regs->orig_gpr2 & mask,
                            regs->gprs[3] &mask, regs->gprs[4] &mask,
                            regs->gprs[5] &mask);
 
+       if ((signed long)regs->gprs[2] >= NR_syscalls) {
+               regs->gprs[2] = -ENOSYS;
+               ret = -ENOSYS;
+       }
        return regs->gprs[2];
+skip:
+       clear_pt_regs_flag(regs, PIF_SYSCALL);
+       return ret;
 }
 
 asmlinkage void do_syscall_trace_exit(struct pt_regs *regs)
-- 
2.25.1