From: Michael Weiser michael.weiser@gmx.de

commit 1962682d2b2fbe6cfa995a85c53c069fadda473e upstream.

Stop printing a (ratelimited) kernel message for each instance of an unimplemented syscall being called. Userland making an unimplemented syscall is not necessarily misbehaviour and to be expected with a current userland running on an older kernel. Also, the current message looks scary to users but does not actually indicate a real problem nor help them narrow down the cause. Just rely on sys_ni_syscall() to return -ENOSYS.

Cc: stable@vger.kernel.org Cc: Martin Vajnar martin.vajnar@gmail.com Cc: musl@lists.openwall.com Acked-by: Will Deacon will.deacon@arm.com Signed-off-by: Michael Weiser michael.weiser@gmx.de Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Arnd Bergmann arnd@arndb.de --- This was backported to v4.14 and later, but is missing in v4.4 and before, apparently because of a trivial merge conflict. This is a manual backport I did after I saw a report about the issue by Martin Vajnar on the musl mailing list. Signed-off-by: Arnd Bergmann arnd@arndb.de --- arch/arm64/kernel/traps.c | 8 -------- 1 file changed, 8 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 9322be69ca09..db4163808c76 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -363,14 +363,6 @@ asmlinkage long do_ni_syscall(struct pt_regs *regs) } #endif

- if (show_unhandled_signals && printk_ratelimit()) { - pr_info("%s[%d]: syscall %d\n", current->comm, - task_pid_nr(current), (int)regs->syscallno); - dump_instr("", regs); - if (user_mode(regs)) - __show_regs(regs); - } - return sys_ni_syscall(); }