[PATCH 2/8] drm/xe/configfs: Fix out-of-bounds read in parse_wa_bb_lines()

[Stuart Summers <stuart.summers@intel.com>]

The outer loop advances the cursor unconditionally at the end of each
iteration. When the last token of a line is terminated by the NUL rather
than by whitespace, e.g. "echo -n 'rcs cmd 1'", the cursor is already on
the NUL and the increment steps past the end of the buffer, so the loop
condition reads out of bounds. The leading strspn(p, " \t\n") already
skips the line separators, and every iteration consumes at least the
engine class token, so dropping the increment keeps the loop making
progress.

Fixes: 39ac06f70062 ("drm/xe/configfs: Add post context restore bb")

Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
---
 drivers/gpu/drm/xe/xe_configfs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_configfs.c b/drivers/gpu/drm/xe/xe_configfs.c
index cc442014cf12..c844155afe52 100644
--- a/drivers/gpu/drm/xe/xe_configfs.c
+++ b/drivers/gpu/drm/xe/xe_configfs.c
@@ -820,7 +820,11 @@ static ssize_t parse_wa_bb_lines(const char *lines,
 	ssize_t dwords = 0, ret;
 	const char *p;
 
-	for (p = lines; *p; p++) {
+	/*
+	 * Each iteration consumes at least the engine class token if it doesn't
+	 * error out, so the loop always makes progress without advancing @p.
+	 */
+	for (p = lines; *p;) {
 		const struct engine_info *info = NULL;
 		u32 val, val2;
 
-- 
2.43.0