From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Olsa Date: Thu, 29 Jun 2017 09:38:11 +0000 Subject: [PATCH] s390/syscalls: Fix out of bounds arguments access Message-Id: <20170629093811.6364-1-jolsa@kernel.org> To: linux-s390@vger.kernel.org List-ID: 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. Reported-by: Zorro Lang Signed-off-by: Jiri Olsa --- arch/s390/include/asm/syscall.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h index 6ba0bf928909..5f7c11c932fa 100644 --- a/arch/s390/include/asm/syscall.h +++ b/arch/s390/include/asm/syscall.h @@ -64,14 +64,22 @@ 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)) mask = 0xffffffff; #endif - while (n-- > 0) + while (n-- > 0) { if (i + n > 0) args[n] = regs->gprs[2 + i + n] & mask; + } + if (i == 0) args[0] = regs->orig_gpr2 & mask; } -- 2.9.4