From: Sven Schnelle svens@linux.ibm.com

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 Signed-off-by: Dan Streetman ddstreet@canonical.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 --- arch/s390/kernel/ptrace.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c index c6aef2ecf289..ad74472ce967 100644 --- 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)