On 3/24/22 21:34, Haowen Bai wrote:
Fix possible indexing array of bound for
port->logbuffer[port->logbuffer_head], where port->logbuffer_head boundary
check happens later. so we do it before.
Signed-off-by: Haowen Bai <baihaowen@xxxxxxxxx>
---
drivers/usb/typec/tcpm/tcpm.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 5fce795..541e9e4 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -591,6 +591,14 @@ static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)
unsigned long rem_nsec;
mutex_lock(&port->logbuffer_lock);
+
+ if (port->logbuffer_head < 0 ||
+ port->logbuffer_head >= LOG_BUFFER_ENTRIES) {
+ dev_warn(port->dev,
+ "Bad log buffer index %d\n", port->logbuffer_head);
+ goto abort;
+ }
+
if (!port->logbuffer[port->logbuffer_head]) {
port->logbuffer[port->logbuffer_head] =
kzalloc(LOG_BUFFER_ENTRY_SIZE, GFP_KERNEL);
@@ -607,13 +615,6 @@ static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)
strcpy(tmpbuffer, "overflow");
}
- if (port->logbuffer_head < 0 ||
- port->logbuffer_head >= LOG_BUFFER_ENTRIES) {
- dev_warn(port->dev,
- "Bad log buffer index %d\n", port->logbuffer_head);
- goto abort;
- }
-
if (!port->logbuffer[port->logbuffer_head]) {
dev_warn(port->dev,
"Log buffer index %d is NULL\n", port->logbuffer_head);
One could argue that the check is unnecessary and can be removed as it can be proven
that it logbuffer_head always in the range of [0, LOG_BUFFER_ENTRIES - 1]. Moving
the check, however, does not add any value unless you can _prove_ that it needs to
be moved, ie that logbuffer_head can be observed to be < 0 or >= LOG_BUFFER_ENTRIES.
I think that is quite unlikely.
Guenter
