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s390/syscalls: Fix out of bounds arguments access

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commit c46fc0424c upstream.

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 <zlang@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Olsa
2017-06-29 11:38:11 +02:00
committed by Greg Kroah-Hartman
parent 1e95148551
commit 8302e9d2f5
1 changed files with 6 additions and 0 deletions
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6
arch/s390/include/asm/syscall.h
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@@ -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))