Commit 2f265fad authored Feb 05, 2018 by Michal Srb Committed by Chris Wilson Feb 05, 2018

drm/i915/cmdparser: Check reg_table_count before derefencing.



The find_reg function was assuming that there is always at least one table in
reg_tables. It is not always true.

In case of VCS or VECS, the reg_tables is NULL and reg_table_count is 0,
implying that no register-accessing commands are allowed. However, the command
tables include commands such as MI_STORE_REGISTER_MEM. When trying to check
such command, the find_reg would dereference NULL pointer.

Now it will just return NULL meaning that the register was not found and the
command will be rejected.

Fixes: 76ff480e ("drm/i915/cmdparser: Use binary search for faster register lookup")
Signed-off-by: Michal Srb <msrb@suse.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180205142916.27092-2-msrb@suse.com


Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180205160438.3267-1-chris@chris-wilson.co.uk
register lookup")

parent 6ec5bd34

drivers/gpu/drm/i915/i915_cmd_parser.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1032,7 +1032,7 @@ find_reg(const struct intel_engine_cs *engine, bool is_master, u32 addr)
		const struct drm_i915_reg_table *table = engine->reg_tables;
		int count = engine->reg_table_count;

		do {
		for (; count > 0; ++table, --count) {
		if (!table->master \|\| is_master) {
		const struct drm_i915_reg_descriptor *reg;

		@@ -1040,7 +1040,7 @@ find_reg(const struct intel_engine_cs *engine, bool is_master, u32 addr)
		if (reg != NULL)
		return reg;
		}
		} while (table++, --count);
		}

		return NULL;
		}