From: Jiri Olsa Date: Thu, 29 Jun 2017 09:38:11 +0000 (+0200) Subject: s390/syscalls: Fix out of bounds arguments access X-Git-Tag: v4.13-rc1~129^2~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=c46fc0424ced3fb71208e72bd597d91b9169a781;p=linux.git s390/syscalls: Fix out of bounds arguments access Zorro reported following crash while having enabled syscall tracing (CONFIG_FTRACE_SYSCALLS): Unable to handle kernel pointer dereference at virtual ... Oops: 0011 [#1] SMP DEBUG_PAGEALLOC SNIP Call Trace: ([<000000000024d79c>] ftrace_syscall_enter+0xec/0x1d8) [<00000000001099c6>] do_syscall_trace_enter+0x236/0x2f8 [<0000000000730f1c>] sysc_tracesys+0x1a/0x32 [<000003fffcf946a2>] 0x3fffcf946a2 INFO: lockdep is turned off. Last Breaking-Event-Address: [<000000000022dd44>] rb_event_data+0x34/0x40 ---[ end trace 8c795f86b1b3f7b9 ]--- The crash happens in syscall_get_arguments function for syscalls with zero arguments, that will try to access first argument (args[0]) in event entry, but it's not allocated. Bail out of there are no arguments. Cc: stable@vger.kernel.org Reported-by: Zorro Lang Signed-off-by: Jiri Olsa Signed-off-by: Martin Schwidefsky --- diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h index 6ba0bf928909..6bc941be6921 100644 --- a/arch/s390/include/asm/syscall.h +++ b/arch/s390/include/asm/syscall.h @@ -64,6 +64,12 @@ static inline void syscall_get_arguments(struct task_struct *task, { unsigned long mask = -1UL; + /* + * No arguments for this syscall, there's nothing to do. + */ + if (!n) + return; + BUG_ON(i + n > 6); #ifdef CONFIG_COMPAT if (test_tsk_thread_flag(task, TIF_31BIT))