This is a note to let you know that I've just added the patch titled
USB: core: Don't hold device lock while reading the "descriptors" sysfs file
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-core-don-t-hold-device-lock-while-reading-the-descriptors-sysfs-file.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 45bf39f8df7f05efb83b302c65ae3b9bc92b7065 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 31 Jan 2023 15:49:04 -0500
Subject: USB: core: Don't hold device lock while reading the "descriptors" sysfs file
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
commit 45bf39f8df7f05efb83b302c65ae3b9bc92b7065 upstream.
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 <troels@xxxxxxxxxxxxxxxx>
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/Y9l+wDTRbuZABzsE@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/core/hub.c | 5 ++---
drivers/usb/core/sysfs.c | 5 -----
2 files changed, 2 insertions(+), 8 deletions(-)
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2322,9 +2322,8 @@ static int usb_enumerate_device_otg(stru
* 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
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -865,11 +865,7 @@ read_descriptors(struct file *filp, stru
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).
@@ -894,7 +890,6 @@ read_descriptors(struct file *filp, stru
off -= srclen;
}
}
- usb_unlock_device(udev);
return count - nleft;
}
Patches currently in stable-queue which might be from stern@xxxxxxxxxxxxxxxxxxx are
queue-4.14/usb-core-don-t-hold-device-lock-while-reading-the-descriptors-sysfs-file.patch
