arch: tile: fix null pointer dereference on pt_regs pointer

Cppcheck reports the following issue:
[arch/tile/kernel/stack.c:116]: (error) Possible null
  pointer dereference: p

In this case, on reporting on an odd fault, p is set to NULL
and immediately afterwords p is dereferenced iff
!kbt->profile is false.  Rather than doing this check just
return NULL rather than falling through to the potential
null pointer dereference (since the original intentional
outcome would be to return NULL anyhow) for this odd fault
case.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com> [tweaked lightly]

diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index 7ff5afd..c42dce5 100644 (file)
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -108,14 +108,15 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
                   p->sp < PAGE_OFFSET && p->sp != 0) {
                if (kbt->verbose)
                        pr_err("  <%s while in user mode>\n", fault);
-       } else if (kbt->verbose) {
-               pr_err("  (odd fault: pc %#lx, sp %#lx, ex1 %#lx?)\n",
-                      p->pc, p->sp, p->ex1);
-               p = NULL;
+       } else {
+               if (kbt->verbose)
+                       pr_err("  (odd fault: pc %#lx, sp %#lx, ex1 %#lx?)\n",
+                              p->pc, p->sp, p->ex1);
+               return NULL;
        }
-       if (!kbt->profile || ((1ULL << p->faultnum) & QUEUED_INTERRUPTS) == 0)
-               return p;
-       return NULL;
+       if (kbt->profile && ((1ULL << p->faultnum) & QUEUED_INTERRUPTS) != 0)
+               return NULL;
+       return p;
 }
 
 /* Is the pc pointing to a sigreturn trampoline? */