From 3f29cbdf3ec2434cc136ba744c020686c8f8062c Mon Sep 17 00:00:00 2001
From: Zhou Qingyang <zhou1615@umn.edu>
Date: Tue, 30 Nov 2021 22:15:44 +0800
Subject: drm/i915/gem: Fix a NULL pointer dereference in igt_request_rewind()
Git-commit: 49a8bf50caa2fb0fb2eb1c89923ea61192227c32
Patch-mainline: v5.17-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
In igt_request_rewind(), mock_context(i915, "A") is assigned to ctx[0]
and used in i915_gem_context_get_engine(). There is a dereference
of ctx[0] in i915_gem_context_get_engine(), which could lead to a NULL
pointer dereference on failure of mock_context(i915, "A") .
So as mock_context(i915, "B").
Although this bug is not serious for it belongs to testing code, it is
better to be fixed to avoid unexpected failure in testing.
Fix this bugs by adding checks about ctx[0] and ctx[1].
This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.
Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.
Builds with CONFIG_DRM_I915_SELFTEST=y show no new warnings,
and our static analyzer no longer warns about this code.
References: 591c0fb85d1c ("drm/i915: Exercise request cancellation using a mock selftest")
[tursulin: Replaced fixes with references to avoid.]
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211130141545.153899-1-zhou1615@umn.edu
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/selftests/i915_request.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c b/drivers/gpu/drm/i915/selftests/i915_request.c
index 6496671a113c..9979ef9197cd 100644
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -209,6 +209,10 @@ static int igt_request_rewind(void *arg)
int err = -EINVAL;
ctx[0] = mock_context(i915, "A");
+ if (!ctx[0]) {
+ err = -ENOMEM;
+ goto err_ctx_0;
+ }
ce = i915_gem_context_get_engine(ctx[0], RCS0);
GEM_BUG_ON(IS_ERR(ce));
@@ -223,6 +227,10 @@ static int igt_request_rewind(void *arg)
i915_request_add(request);
ctx[1] = mock_context(i915, "B");
+ if (!ctx[1]) {
+ err = -ENOMEM;
+ goto err_ctx_1;
+ }
ce = i915_gem_context_get_engine(ctx[1], RCS0);
GEM_BUG_ON(IS_ERR(ce));
@@ -261,9 +269,11 @@ static int igt_request_rewind(void *arg)
i915_request_put(vip);
err_context_1:
mock_context_close(ctx[1]);
+err_ctx_1:
i915_request_put(request);
err_context_0:
mock_context_close(ctx[0]);
+err_ctx_0:
mock_device_flush(i915);
return err;
}
--
2.38.1