Hello Yueyao Zhu,
The patch c034a43e72dd: "staging: typec: Fairchild FUSB302 Type-c
chip driver" from Apr 27, 2017, leads to the following static checker
warning:
drivers/staging/typec/fusb302/fusb302.c:180 _fusb302_log()
error: testing array offset 'chip->logbuffer_head' after use.
drivers/staging/typec/fusb302/fusb302.c
156 static void _fusb302_log(struct fusb302_chip *chip, const char *fmt,
157 va_list args)
158 {
159 char tmpbuffer[LOG_BUFFER_ENTRY_SIZE];
160 u64 ts_nsec = local_clock();
161 unsigned long rem_nsec;
162
163 if (!chip->logbuffer[chip->logbuffer_head]) {
164 chip->logbuffer[chip->logbuffer_head] =
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Writing to array offset.
165 kzalloc(LOG_BUFFER_ENTRY_SIZE, GFP_KERNEL);
166 if (!chip->logbuffer[chip->logbuffer_head])
167 return;
168 }
169
170 vsnprintf(tmpbuffer, sizeof(tmpbuffer), fmt, args);
171
172 mutex_lock(&chip->logbuffer_lock);
173
174 if (fusb302_log_full(chip)) {
175 chip->logbuffer_head = max(chip->logbuffer_head - 1, 0);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
We decrement chip->logbuffer_head unless it's already 0.
176 strlcpy(tmpbuffer, "overflow", sizeof(tmpbuffer));
177 }
178
179 if (chip->logbuffer_head < 0 ||
180 chip->logbuffer_head >= LOG_BUFFER_ENTRIES) {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This test is too late. But it looks like we can just delete it since it
can never be true.
181 dev_warn(chip->dev,
182 "Bad log buffer index %d\n", chip->logbuffer_head);
183 goto abort;
184 }
185
regards,
dan carpenter
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