From ab25d94e88082d3cd6870b8338da55da42e3cf5e Mon Sep 17 00:00:00 2001 From: Uttkarsh Aggarwal Date: Thu, 25 May 2023 14:58:54 +0530 Subject: [PATCH] UPSTREAM: usb: gadget: f_fs: Add unbind event before functionfs_unbind While exercising the unbind path, with the current implementation the functionfs_unbind would be calling which waits for the ffs->mutex to be available, however within the same time ffs_ep0_read is invoked & if no setup packets are pending, it will invoke function wait_event_interruptible_exclusive_locked_irq which by definition waits for the ev.count to be increased inside the same mutex for which functionfs_unbind is waiting. This creates deadlock situation because the functionfs_unbind won't get the lock until ev.count is increased which can only happen if the caller ffs_func_unbind can proceed further. Following is the illustration: CPU1 CPU2 ffs_func_unbind() ffs_ep0_read() mutex_lock(ffs->mutex) wait_event(ffs->ev.count) functionfs_unbind() mutex_lock(ffs->mutex) mutex_unlock(ffs->mutex) ffs_event_add() Fix this by moving the event unbind before functionfs_unbind to ensure the ev.count is incrased properly. Fixes: 6a19da111057 ("usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait") Cc: stable Signed-off-by: Uttkarsh Aggarwal Link: https://lore.kernel.org/r/20230525092854.7992-1-quic_uaggarwa@quicinc.com Signed-off-by: Greg Kroah-Hartman Bug: 285072336 (cherry picked from commit efb6b535207395a5c7317993602e2503ca8cb4b3) Change-Id: Iae8cbdacc64810b3a63f77d0510b61fb39d10ae8 Signed-off-by: Uttkarsh Aggarwal --- drivers/usb/gadget/function/f_fs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 53154a6fd9fb..deaba9128949 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -3619,6 +3619,7 @@ static void ffs_func_unbind(struct usb_configuration *c, /* Drain any pending AIO completions */ drain_workqueue(ffs->io_completion_wq); + ffs_event_add(ffs, FUNCTIONFS_UNBIND); if (!--opts->refcnt) functionfs_unbind(ffs); @@ -3643,7 +3644,6 @@ static void ffs_func_unbind(struct usb_configuration *c, func->function.ssp_descriptors = NULL; func->interfaces_nums = NULL; - ffs_event_add(ffs, FUNCTIONFS_UNBIND); } static struct usb_function *ffs_alloc(struct usb_function_instance *fi)