From 45bf39f8df7f05efb83b302c65ae3b9bc92b7065 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Tue, 31 Jan 2023 15:49:04 -0500 Subject: [PATCH] USB: core: Don't hold device lock while reading the "descriptors" sysfs file Ever since commit 83e83ecb79a8 ("usb: core: get config and string descriptors for unauthorized devices") was merged in 2013, there has been no mechanism for reallocating the rawdescriptors buffers in struct usb_device after the initial enumeration. Before that commit, the buffers would be deallocated when a device was deauthorized and reallocated when it was authorized and enumerated. This means that the locking in the read_descriptors() routine is not needed, since the buffers it reads will never be reallocated while the routine is running. This locking can interfere with user programs trying to read a hub's descriptors via sysfs while new child devices of the hub are being initialized, since the hub is locked during this procedure. Since the locking in read_descriptors() hasn't been needed for over nine years, we can remove it. Reported-and-tested-by: Troels Liebe Bentsen Signed-off-by: Alan Stern CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/Y9l+wDTRbuZABzsE@rowland.harvard.edu Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hub.c | 5 ++--- drivers/usb/core/sysfs.c | 5 ----- 2 files changed, 2 insertions(+), 8 deletions(-) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 9eca403..97a0f8f 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -2389,9 +2389,8 @@ static int usb_enumerate_device_otg(struct usb_device *udev) * usb_enumerate_device - Read device configs/intfs/otg (usbcore-internal) * @udev: newly addressed device (in ADDRESS state) * - * This is only called by usb_new_device() and usb_authorize_device() - * and FIXME -- all comments that apply to them apply here wrt to - * environment. + * This is only called by usb_new_device() -- all comments that apply there + * apply here wrt to environment. * * If the device is WUSB and not authorized, we don't attempt to read * the string descriptors, as they will be errored out by the device diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c index 8217032..b63f78e 100644 --- a/drivers/usb/core/sysfs.c +++ b/drivers/usb/core/sysfs.c @@ -869,11 +869,7 @@ read_descriptors(struct file *filp, struct kobject *kobj, size_t srclen, n; int cfgno; void *src; - int retval; - retval = usb_lock_device_interruptible(udev); - if (retval < 0) - return -EINTR; /* The binary attribute begins with the device descriptor. * Following that are the raw descriptor entries for all the * configurations (config plus subsidiary descriptors). @@ -898,7 +894,6 @@ read_descriptors(struct file *filp, struct kobject *kobj, off -= srclen; } } - usb_unlock_device(udev); return count - nleft; } -- 2.7.4