===================================================================
@@ -5163,7 +5163,7 @@ static void hub_port_connect_change(stru
/* Handle notifying userspace about hub over-current events */
static void port_over_current_notify(struct usb_port *port_dev)
{
- static char *envp[] = { NULL, NULL, NULL };
+ char *envp[3];
struct device *hub_dev;
char *port_dev_path;
@@ -5187,6 +5187,7 @@ static void port_over_current_notify(str
if (!envp[1])
goto exit;
+ envp[2] = NULL;
kobject_uevent_env(&hub_dev->kobj, KOBJ_CHANGE, envp);
kfree(envp[1]);
Syzbot and KASAN found the following invalid-free bug in port_over_current_notify(): -------------------------------------------------------------------------- BUG: KASAN: double-free or invalid-free in port_over_current_notify drivers/usb/core/hub.c:5192 [inline] BUG: KASAN: double-free or invalid-free in port_event drivers/usb/core/hub.c:5241 [inline] BUG: KASAN: double-free or invalid-free in hub_event+0xd97/0x4140 drivers/usb/core/hub.c:5384 CPU: 1 PID: 32710 Comm: kworker/1:3 Not tainted 4.20.0-rc3+ #129 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: usb_hub_wq hub_event Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256 kasan_report_invalid_free+0x64/0xa0 mm/kasan/report.c:336 __kasan_slab_free+0x13a/0x150 mm/kasan/kasan.c:501 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3498 [inline] kfree+0xcf/0x230 mm/slab.c:3817 port_over_current_notify drivers/usb/core/hub.c:5192 [inline] port_event drivers/usb/core/hub.c:5241 [inline] hub_event+0xd97/0x4140 drivers/usb/core/hub.c:5384 process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153 worker_thread+0x17f/0x1390 kernel/workqueue.c:2296 kthread+0x35a/0x440 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 -------------------------------------------------------------------------- The problem is caused by use of a static array to store environment-string pointers. When the routine is called by multiple threads concurrently, the pointers from one thread can overwrite those from another. The solution is to use an ordinary automatic array instead of a static array. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-by: syzbot+98881958e1410ec7e53c@syzkaller.appspotmail.com --- [as1881] drivers/usb/core/hub.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)