6.6-stable review patch. If anyone has any objections, please let me know.
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From: Eli Billauer eli.billauer@gmail.com
commit ccbde4b128ef9c73d14d0d7817d68ef795f6d131 upstream.
Triggered by a kref decrement, destroy_workqueue() may be called from within a work item for destroying its own workqueue. This illegal situation is averted by adding a module-global workqueue for exclusive use of the offending work item. Other work items continue to be queued on per-device workqueues to ensure performance.
Reported-by: syzbot+91dbdfecdd3287734d8e@syzkaller.appspotmail.com Cc: stable stable@kernel.org Closes: https://lore.kernel.org/lkml/0000000000000ab25a061e1dfe9f@google.com/ Signed-off-by: Eli Billauer eli.billauer@gmail.com Link: https://lore.kernel.org/r/20240801121126.60183-1-eli.billauer@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/xillybus/xillyusb.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
--- a/drivers/char/xillybus/xillyusb.c +++ b/drivers/char/xillybus/xillyusb.c @@ -50,6 +50,7 @@ MODULE_LICENSE("GPL v2"); static const char xillyname[] = "xillyusb";
static unsigned int fifo_buf_order; +static struct workqueue_struct *wakeup_wq;
#define USB_VENDOR_ID_XILINX 0x03fd #define USB_VENDOR_ID_ALTERA 0x09fb @@ -569,10 +570,6 @@ static void cleanup_dev(struct kref *kre * errors if executed. The mechanism relies on that xdev->error is assigned * a non-zero value by report_io_error() prior to queueing wakeup_all(), * which prevents bulk_in_work() from calling process_bulk_in(). - * - * The fact that wakeup_all() and bulk_in_work() are queued on the same - * workqueue makes their concurrent execution very unlikely, however the - * kernel's API doesn't seem to ensure this strictly. */
static void wakeup_all(struct work_struct *work) @@ -627,7 +624,7 @@ static void report_io_error(struct xilly
if (do_once) { kref_get(&xdev->kref); /* xdev is used by work item */ - queue_work(xdev->workq, &xdev->wakeup_workitem); + queue_work(wakeup_wq, &xdev->wakeup_workitem); } }
@@ -2258,6 +2255,10 @@ static int __init xillyusb_init(void) { int rc = 0;
+ wakeup_wq = alloc_workqueue(xillyname, 0, 0); + if (!wakeup_wq) + return -ENOMEM; + if (LOG2_INITIAL_FIFO_BUF_SIZE > PAGE_SHIFT) fifo_buf_order = LOG2_INITIAL_FIFO_BUF_SIZE - PAGE_SHIFT; else @@ -2265,11 +2266,16 @@ static int __init xillyusb_init(void)
rc = usb_register(&xillyusb_driver);
+ if (rc) + destroy_workqueue(wakeup_wq); + return rc; }
static void __exit xillyusb_exit(void) { + destroy_workqueue(wakeup_wq); + usb_deregister(&xillyusb_driver); }