s390/ptrace: return -ENOSYS when invalid syscall is supplied

commit cd29fa798001075a554b978df3a64e6656c25794 upstream.

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 <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1895132
[krzysztof: adjusted the backport around missing ifdef CONFIG_SECCOMP,
 add Link and Fixes; apparently this should go with the referenced commit]
Fixes: 00332c16b160 ("s390/ptrace: pass invalid syscall numbers to tracing")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index c6aef2ecf2890383a31a6b88636bf9c09c33d608..ad74472ce967e7ac10c2d403dcd85d399f122cda 100644 (file)
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -867,6 +867,7 @@ 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;
 
        /*
         * The sysc_tracesys code in entry.S stored the system
@@ -878,27 +879,33 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
                 * Tracing decided this syscall should not happen. Skip
                 * the system call and the system call restart handling.
                 */
-               clear_pt_regs_flag(regs, PIF_SYSCALL);
-               return -1;
+               goto skip;
        }
 
        /* Do the secure computing check after ptrace. */
        if (secure_computing(NULL)) {
                /* seccomp failures shouldn't expose any additional code. */
-               return -1;
+               goto skip;
        }
 
        if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
-               trace_sys_enter(regs, regs->gprs[2]);
+               trace_sys_enter(regs, regs->int_code & 0xffff);
 
        if (is_compat_task())
                mask = 0xffffffff;
 
-       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)