[PATCH] drm/i915/gt: Protect against overflow in active_engine()

[Krzysztof Karas]

It is unlikely, but possible for the first call to
intel_context_create() to fail with -ENOMEM, which would result
in entering the following code block and decrementing "count",
when it is set to 0 (initial condition in the for loop).

Protect from overflowing the variable with additional count > 0
check.

Signed-off-by: Krzysztof Karas <krzysztof.ka...@intel.com>
---
 drivers/gpu/drm/i915/gt/selftest_hangcheck.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c 
b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
index f057c16410e7..cc0798dd30d5 100644
--- a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
+++ b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
@@ -904,8 +904,10 @@ static void active_engine(struct kthread_work *work)
                        arg->result = PTR_ERR(ce[count]);
                        pr_err("[%s] Create context #%ld failed: %d!\n",
                               engine->name, count, arg->result);
-                       while (--count)
-                               intel_context_put(ce[count]);
+                       if (likely(count > 0)) {
+                               while (--count)
+                                       intel_context_put(ce[count]);
+                       }
                        return;
                }
        }
-- 
2.34.1

-- 
Best Regards,
Krzysztof