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author | Uttkarsh Aggarwal <quic_uaggarwa@quicinc.com> | 2023-05-25 14:58:54 +0530 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-06-09 10:34:20 +0200 |
commit | 704842c97aa35e587a287c22c57582a330dd0f57 (patch) | |
tree | 560c1935c34b102b8035db88257186c3ad99657d /drivers/usb | |
parent | cc8c9864da6986463627a2ba1a1c8a8ac6589988 (diff) | |
download | linux-704842c97aa35e587a287c22c57582a330dd0f57.tar.gz |
usb: gadget: f_fs: Add unbind event before functionfs_unbind
commit efb6b535207395a5c7317993602e2503ca8cb4b3 upstream. 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() <deadlock> 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 <stable@kernel.org> Signed-off-by: Uttkarsh Aggarwal <quic_uaggarwa@quicinc.com> Link: https://lore.kernel.org/r/20230525092854.7992-1-quic_uaggarwa@quicinc.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
-rw-r--r-- | drivers/usb/gadget/function/f_fs.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 8ad354741380..3e59055aa504 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -3620,6 +3620,7 @@ 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); @@ -3644,7 +3645,6 @@ 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) |