<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/drivers/usb/gadget/udc, branch master</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>usb: gadget: dummy_hcd: Reject hub port requests for non-existent ports</title>
<updated>2026-05-22T09:13:31+00:00</updated>
<author>
<name>Seungjin Bae</name>
<email>eeodqql09@gmail.com</email>
</author>
<published>2026-05-18T23:43:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=7d9633528dd40e33964d2dc74a5abbf5c4d116ce'/>
<id>7d9633528dd40e33964d2dc74a5abbf5c4d116ce</id>
<content type='text'>
The `dummy_hub_control()` function handles USB hub class requests
to the virtual root hub. The `GetPortStatus` case returns -EPIPE for
requests with `wIndex != 1`, since the virtual root hub has only a
single port. However, the `ClearPortFeature` and `SetPortFeature`
cases lack the same check.

Fix this by extending the `wIndex != 1` rejection to both cases,
matching the existing behavior of `GetPortStatus`.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable &lt;stable@kernel.org&gt;
Suggested-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Signed-off-by: Seungjin Bae &lt;eeodqql09@gmail.com&gt;
Reviewed-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Link: https://patch.msgid.link/20260518234314.1889396-1-eeodqql09@gmail.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The `dummy_hub_control()` function handles USB hub class requests
to the virtual root hub. The `GetPortStatus` case returns -EPIPE for
requests with `wIndex != 1`, since the virtual root hub has only a
single port. However, the `ClearPortFeature` and `SetPortFeature`
cases lack the same check.

Fix this by extending the `wIndex != 1` rejection to both cases,
matching the existing behavior of `GetPortStatus`.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable &lt;stable@kernel.org&gt;
Suggested-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Signed-off-by: Seungjin Bae &lt;eeodqql09@gmail.com&gt;
Reviewed-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Link: https://patch.msgid.link/20260518234314.1889396-1-eeodqql09@gmail.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: net2280: Fix double free in probe error path</title>
<updated>2026-05-22T08:35:22+00:00</updated>
<author>
<name>Guangshuo Li</name>
<email>lgs201920130244@gmail.com</email>
</author>
<published>2026-04-27T15:36:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=c8547c74988e0b5f4cbb1b895e2a57aae084f070'/>
<id>c8547c74988e0b5f4cbb1b895e2a57aae084f070</id>
<content type='text'>
usb_initialize_gadget() installs gadget_release() as the release
callback for the embedded gadget device.  The struct net2280 instance is
therefore released through gadget_release() when the gadget device's last
reference is dropped.

The probe error path calls net2280_remove(), which tears down the
partially initialized device and drops the gadget reference with
usb_put_gadget().  Calling kfree(dev) afterwards can free the same object
again.

Drop the explicit kfree() and let the gadget device release callback
handle the final free.  This issue was found by a static analysis tool
I am developing.

Fixes: f770fbec4165 ("USB: UDC: net2280: Fix memory leaks")
Cc: stable &lt;stable@kernel.org&gt;
Signed-off-by: Guangshuo Li &lt;lgs201920130244@gmail.com&gt;
Reviewed-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Link: https://patch.msgid.link/20260427153651.337846-1-lgs201920130244@gmail.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
usb_initialize_gadget() installs gadget_release() as the release
callback for the embedded gadget device.  The struct net2280 instance is
therefore released through gadget_release() when the gadget device's last
reference is dropped.

The probe error path calls net2280_remove(), which tears down the
partially initialized device and drops the gadget reference with
usb_put_gadget().  Calling kfree(dev) afterwards can free the same object
again.

Drop the explicit kfree() and let the gadget device release callback
handle the final free.  This issue was found by a static analysis tool
I am developing.

Fixes: f770fbec4165 ("USB: UDC: net2280: Fix memory leaks")
Cc: stable &lt;stable@kernel.org&gt;
Signed-off-by: Guangshuo Li &lt;lgs201920130244@gmail.com&gt;
Reviewed-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Link: https://patch.msgid.link/20260427153651.337846-1-lgs201920130244@gmail.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>USB: omap_udc: DMA: Don't enable burst 4 mode</title>
<updated>2026-04-27T15:49:28+00:00</updated>
<author>
<name>Aaro Koskinen</name>
<email>aaro.koskinen@iki.fi</email>
</author>
<published>2026-04-13T18:49:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=3f91484f6c13c434bd573ca6b6779c26adb0ddab'/>
<id>3f91484f6c13c434bd573ca6b6779c26adb0ddab</id>
<content type='text'>
Commit 65111084c63d7 ("USB: more omap_udc updates (dma and omap1710)")
added setting for DMA burst 4 mode. But I think this should be undone for
two reasons:

- It breaks DMA on 15xx boards - transfers just silently stall.

- On newer OMAP1 boards, like Nokia 770 (omap1710), there is no measurable
performance impact when testing TCP throughput with g_ether with large
15000 byte MTU size.

It's also worth noting that when the original change was made, the
OMAP_DMA_DATA_BURST_4 handling in arch/arm/plat-omap/dma.c was broken, and
actually resulted in the same as the OMAP_DMA_DATA_BURST_DIS i.e. burst
disabled. This was fixed not until a couple kernel releases later in an
unrelated commit 1a8bfa1eb998a ("[ARM] 3142/1: OMAP 2/5: Update files
common to omap1 and omap2").

So based on this it seems there was never really a very good reason to
enable this burst mode in omap_udc, so remove it now to allow 15xx DMA
to work again (it provides 2x throughput compared to PIO mode).

Fixes: 65111084c63d ("[PATCH] USB: more omap_udc updates (dma and omap1710)")
Cc: stable &lt;stable@kernel.org&gt;
Signed-off-by: Aaro Koskinen &lt;aaro.koskinen@iki.fi&gt;
Link: https://patch.msgid.link/ad06qHLclWHeSGnV@darkstar.musicnaut.iki.fi
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Commit 65111084c63d7 ("USB: more omap_udc updates (dma and omap1710)")
added setting for DMA burst 4 mode. But I think this should be undone for
two reasons:

- It breaks DMA on 15xx boards - transfers just silently stall.

- On newer OMAP1 boards, like Nokia 770 (omap1710), there is no measurable
performance impact when testing TCP throughput with g_ether with large
15000 byte MTU size.

It's also worth noting that when the original change was made, the
OMAP_DMA_DATA_BURST_4 handling in arch/arm/plat-omap/dma.c was broken, and
actually resulted in the same as the OMAP_DMA_DATA_BURST_DIS i.e. burst
disabled. This was fixed not until a couple kernel releases later in an
unrelated commit 1a8bfa1eb998a ("[ARM] 3142/1: OMAP 2/5: Update files
common to omap1 and omap2").

So based on this it seems there was never really a very good reason to
enable this burst mode in omap_udc, so remove it now to allow 15xx DMA
to work again (it provides 2x throughput compared to PIO mode).

Fixes: 65111084c63d ("[PATCH] USB: more omap_udc updates (dma and omap1710)")
Cc: stable &lt;stable@kernel.org&gt;
Signed-off-by: Aaro Koskinen &lt;aaro.koskinen@iki.fi&gt;
Link: https://patch.msgid.link/ad06qHLclWHeSGnV@darkstar.musicnaut.iki.fi
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: renesas_usb3: validate endpoint index in standard request handlers</title>
<updated>2026-04-07T11:48:30+00:00</updated>
<author>
<name>Greg Kroah-Hartman</name>
<email>gregkh@linuxfoundation.org</email>
</author>
<published>2026-04-06T15:09:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=f880aac8a57ebd92abfa685d45424b2998ac1059'/>
<id>f880aac8a57ebd92abfa685d45424b2998ac1059</id>
<content type='text'>
The GET_STATUS and SET/CLEAR_FEATURE handlers extract the endpoint
number from the host-supplied wIndex without any sort of validation.
Fix this up by validating the number of endpoints actually match up with
the number the device has before attempting to dereference a pointer
based on this math.

This is just like what was done in commit ee0d382feb44 ("usb: gadget:
aspeed_udc: validate endpoint index for ast udc") for the aspeed driver.

Fixes: 746bfe63bba3 ("usb: gadget: renesas_usb3: add support for Renesas USB3.0 peripheral controller")
Cc: stable &lt;stable@kernel.org&gt;
Assisted-by: gregkh_clanker_t1000
Link: https://patch.msgid.link/2026040647-sincerity-untidy-b104@gregkh
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The GET_STATUS and SET/CLEAR_FEATURE handlers extract the endpoint
number from the host-supplied wIndex without any sort of validation.
Fix this up by validating the number of endpoints actually match up with
the number the device has before attempting to dereference a pointer
based on this math.

This is just like what was done in commit ee0d382feb44 ("usb: gadget:
aspeed_udc: validate endpoint index for ast udc") for the aspeed driver.

Fixes: 746bfe63bba3 ("usb: gadget: renesas_usb3: add support for Renesas USB3.0 peripheral controller")
Cc: stable &lt;stable@kernel.org&gt;
Assisted-by: gregkh_clanker_t1000
Link: https://patch.msgid.link/2026040647-sincerity-untidy-b104@gregkh
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'v7.0-rc7' into usb-next</title>
<updated>2026-04-06T07:06:39+00:00</updated>
<author>
<name>Greg Kroah-Hartman</name>
<email>gregkh@linuxfoundation.org</email>
</author>
<published>2026-04-06T07:06:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=3723393cc284e09107c0f55c47458b75b29be2c3'/>
<id>3723393cc284e09107c0f55c47458b75b29be2c3</id>
<content type='text'>
We need the USB fixes in here to build on and for testing

Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
We need the USB fixes in here to build on and for testing

Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: udc: update outdated comment for renamed usb_gadget_udc_start()</title>
<updated>2026-03-30T14:50:09+00:00</updated>
<author>
<name>Kexin Sun</name>
<email>kexinsun@smail.nju.edu.cn</email>
</author>
<published>2026-03-21T11:00:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=091ef6f503f49cdb3b19542b23f3cfd3e80a5f11'/>
<id>091ef6f503f49cdb3b19542b23f3cfd3e80a5f11</id>
<content type='text'>
The function usb_gadget_udc_start() was renamed to
usb_gadget_udc_start_locked() by commit 286d9975a838 ("usb: gadget:
udc: core: Prevent soft_connect_store() race").  Update the comment
in usb_gadget_udc_set_speed() accordingly.

Assisted-by: unnamed:deepseek-v3.2 coccinelle
Signed-off-by: Kexin Sun &lt;kexinsun@smail.nju.edu.cn&gt;
Link: https://patch.msgid.link/20260321110006.8484-1-kexinsun@smail.nju.edu.cn
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The function usb_gadget_udc_start() was renamed to
usb_gadget_udc_start_locked() by commit 286d9975a838 ("usb: gadget:
udc: core: Prevent soft_connect_store() race").  Update the comment
in usb_gadget_udc_set_speed() accordingly.

Assisted-by: unnamed:deepseek-v3.2 coccinelle
Signed-off-by: Kexin Sun &lt;kexinsun@smail.nju.edu.cn&gt;
Link: https://patch.msgid.link/20260321110006.8484-1-kexinsun@smail.nju.edu.cn
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: bdc: validate status-report endpoint indices</title>
<updated>2026-03-30T14:47:45+00:00</updated>
<author>
<name>Pengpeng Hou</name>
<email>pengpeng@iscas.ac.cn</email>
</author>
<published>2026-03-23T12:17:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a402532ab855620e02a16950aea86fc621c6f87c'/>
<id>a402532ab855620e02a16950aea86fc621c6f87c</id>
<content type='text'>
bdc_sr_xsf() decodes a 5-bit endpoint number from the hardware status
report and uses it to index bdc-&gt;bdc_ep_array[] directly. The array is
only allocated to bdc-&gt;num_eps for the current controller instance, so a
status report can carry an endpoint number that still fits the 5-bit
field but does not fit the runtime-sized endpoint table.

Reject status reports whose endpoint number is outside bdc-&gt;num_eps
before indexing the endpoint array.

Signed-off-by: Pengpeng Hou &lt;pengpeng@iscas.ac.cn&gt;
Reviewed-by: Florian Fainelli &lt;florian.fainelli@broadcom.com&gt;
Tested-by: Justin Chen &lt;justin.chen@broadcom.com&gt;
Link: https://patch.msgid.link/20260323121730.75245-1-pengpeng@iscas.ac.cn
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
bdc_sr_xsf() decodes a 5-bit endpoint number from the hardware status
report and uses it to index bdc-&gt;bdc_ep_array[] directly. The array is
only allocated to bdc-&gt;num_eps for the current controller instance, so a
status report can carry an endpoint number that still fits the 5-bit
field but does not fit the runtime-sized endpoint table.

Reject status reports whose endpoint number is outside bdc-&gt;num_eps
before indexing the endpoint array.

Signed-off-by: Pengpeng Hou &lt;pengpeng@iscas.ac.cn&gt;
Reviewed-by: Florian Fainelli &lt;florian.fainelli@broadcom.com&gt;
Tested-by: Justin Chen &lt;justin.chen@broadcom.com&gt;
Link: https://patch.msgid.link/20260323121730.75245-1-pengpeng@iscas.ac.cn
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>usb: gadget: dummy_hcd: fix premature URB completion when ZLP follows partial transfer</title>
<updated>2026-03-18T15:19:33+00:00</updated>
<author>
<name>Sebastian Urban</name>
<email>surban@surban.net</email>
</author>
<published>2026-03-15T15:10:45+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=f50200dd44125e445a6164e88c217472fa79cdbc'/>
<id>f50200dd44125e445a6164e88c217472fa79cdbc</id>
<content type='text'>
When a gadget request is only partially transferred in transfer()
because the per-frame bandwidth budget is exhausted, the loop advances
to the next queued request. If that next request is a zero-length
packet (ZLP), len evaluates to zero and the code takes the
unlikely(len == 0) path, which sets is_short = 1. This bypasses the
bandwidth guard ("limit &lt; ep-&gt;ep.maxpacket &amp;&amp; limit &lt; len") that
lives in the else branch and would otherwise break out of the loop for
non-zero requests. The is_short path then completes the URB before all
data from the first request has been transferred.

Reproducer (bulk IN, high speed):

  Device side (FunctionFS with Linux AIO):
    1. Queue a 65024-byte write via io_submit (127 * 512, i.e. a
       multiple of the HS bulk max packet size).
    2. Immediately queue a zero-length write (ZLP) via io_submit.

  Host side:
    3. Submit a 65536-byte bulk IN URB.

  Expected: URB completes with actual_length = 65024.
  Actual:   URB completes with actual_length = 53248, losing 11776
            bytes that leak into subsequent URBs.

At high speed the per-frame budget is 53248 bytes (512 * 13 * 8).
The 65024-byte request exhausts this budget after 53248 bytes, leaving
the request incomplete (req-&gt;req.actual &lt; req-&gt;req.length). Neither
the request nor the URB is finished, and rescan is 0, so the loop
advances to the ZLP. For the ZLP, dev_len = 0, so len = min(12288, 0)
= 0, taking the unlikely(len == 0) path and setting is_short = 1.
The is_short handler then sets *status = 0, completing the URB with
only 53248 of the expected 65024 bytes.

Fix this by breaking out of the loop when the current request has
remaining data (req-&gt;req.actual &lt; req-&gt;req.length). The request
resumes on the next timer tick, preserving correct data ordering.

Signed-off-by: Sebastian Urban &lt;surban@surban.net&gt;
Cc: stable &lt;stable@kernel.org&gt;
Reviewed-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Link: https://patch.msgid.link/20260315151045.1155850-1-surban@surban.net
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When a gadget request is only partially transferred in transfer()
because the per-frame bandwidth budget is exhausted, the loop advances
to the next queued request. If that next request is a zero-length
packet (ZLP), len evaluates to zero and the code takes the
unlikely(len == 0) path, which sets is_short = 1. This bypasses the
bandwidth guard ("limit &lt; ep-&gt;ep.maxpacket &amp;&amp; limit &lt; len") that
lives in the else branch and would otherwise break out of the loop for
non-zero requests. The is_short path then completes the URB before all
data from the first request has been transferred.

Reproducer (bulk IN, high speed):

  Device side (FunctionFS with Linux AIO):
    1. Queue a 65024-byte write via io_submit (127 * 512, i.e. a
       multiple of the HS bulk max packet size).
    2. Immediately queue a zero-length write (ZLP) via io_submit.

  Host side:
    3. Submit a 65536-byte bulk IN URB.

  Expected: URB completes with actual_length = 65024.
  Actual:   URB completes with actual_length = 53248, losing 11776
            bytes that leak into subsequent URBs.

At high speed the per-frame budget is 53248 bytes (512 * 13 * 8).
The 65024-byte request exhausts this budget after 53248 bytes, leaving
the request incomplete (req-&gt;req.actual &lt; req-&gt;req.length). Neither
the request nor the URB is finished, and rescan is 0, so the loop
advances to the ZLP. For the ZLP, dev_len = 0, so len = min(12288, 0)
= 0, taking the unlikely(len == 0) path and setting is_short = 1.
The is_short handler then sets *status = 0, completing the URB with
only 53248 of the expected 65024 bytes.

Fix this by breaking out of the loop when the current request has
remaining data (req-&gt;req.actual &lt; req-&gt;req.length). The request
resumes on the next timer tick, preserving correct data ordering.

Signed-off-by: Sebastian Urban &lt;surban@surban.net&gt;
Cc: stable &lt;stable@kernel.org&gt;
Reviewed-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Link: https://patch.msgid.link/20260315151045.1155850-1-surban@surban.net
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>USB: dummy-hcd: Fix interrupt synchronization error</title>
<updated>2026-03-18T15:16:33+00:00</updated>
<author>
<name>Alan Stern</name>
<email>stern@rowland.harvard.edu</email>
</author>
<published>2026-03-15T18:31:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2ca9e46f8f1f5a297eb0ac83f79d35d5b3a02541'/>
<id>2ca9e46f8f1f5a297eb0ac83f79d35d5b3a02541</id>
<content type='text'>
This fixes an error in synchronization in the dummy-hcd driver.  The
error has a somewhat involved history.  The synchronization mechanism
was introduced by commit 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous
synchronization change"), which added an emulated "interrupts enabled"
flag together with code emulating synchronize_irq() (it waits until
all current handler callbacks have returned).

But the emulated interrupt-disable occurred too late, after the driver
containing the handler callback routines had been told that it was
unbound and no more callbacks would occur.  Commit 4a5d797a9f9c ("usb:
gadget: dummy_hcd: fix gpf in gadget_setup") tried to fix this by
moving the synchronize_irq() emulation code from dummy_stop() to
dummy_pullup(), which runs before the unbind callback.

There still were races, though, because the emulated interrupt-disable
still occurred too late.  It couldn't be moved to dummy_pullup(),
because that routine can be called for reasons other than an impending
unbind.  Therefore commits 7dc0c55e9f30 ("USB: UDC core: Add
udc_async_callbacks gadget op") and 04145a03db9d ("USB: UDC: Implement
udc_async_callbacks in dummy-hcd") added an API allowing the UDC core
to tell dummy-hcd exactly when emulated interrupts and their callbacks
should be disabled.

That brings us to the current state of things, which is still wrong
because the emulated synchronize_irq() occurs before the emulated
interrupt-disable!  That's no good, beause it means that more emulated
interrupts can occur after the synchronize_irq() emulation has run,
leading to the possibility that a callback handler may be running when
the gadget driver is unbound.

To fix this, we have to move the synchronize_irq() emulation code yet
again, to the dummy_udc_async_callbacks() routine, which takes care of
enabling and disabling emulated interrupt requests.  The
synchronization will now run immediately after emulated interrupts are
disabled, which is where it belongs.

Signed-off-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Fixes: 04145a03db9d ("USB: UDC: Implement udc_async_callbacks in dummy-hcd")
Cc: stable &lt;stable@kernel.org&gt;
Link: https://patch.msgid.link/c7bc93fe-4241-4d04-bd56-27c12ba35c97@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This fixes an error in synchronization in the dummy-hcd driver.  The
error has a somewhat involved history.  The synchronization mechanism
was introduced by commit 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous
synchronization change"), which added an emulated "interrupts enabled"
flag together with code emulating synchronize_irq() (it waits until
all current handler callbacks have returned).

But the emulated interrupt-disable occurred too late, after the driver
containing the handler callback routines had been told that it was
unbound and no more callbacks would occur.  Commit 4a5d797a9f9c ("usb:
gadget: dummy_hcd: fix gpf in gadget_setup") tried to fix this by
moving the synchronize_irq() emulation code from dummy_stop() to
dummy_pullup(), which runs before the unbind callback.

There still were races, though, because the emulated interrupt-disable
still occurred too late.  It couldn't be moved to dummy_pullup(),
because that routine can be called for reasons other than an impending
unbind.  Therefore commits 7dc0c55e9f30 ("USB: UDC core: Add
udc_async_callbacks gadget op") and 04145a03db9d ("USB: UDC: Implement
udc_async_callbacks in dummy-hcd") added an API allowing the UDC core
to tell dummy-hcd exactly when emulated interrupts and their callbacks
should be disabled.

That brings us to the current state of things, which is still wrong
because the emulated synchronize_irq() occurs before the emulated
interrupt-disable!  That's no good, beause it means that more emulated
interrupts can occur after the synchronize_irq() emulation has run,
leading to the possibility that a callback handler may be running when
the gadget driver is unbound.

To fix this, we have to move the synchronize_irq() emulation code yet
again, to the dummy_udc_async_callbacks() routine, which takes care of
enabling and disabling emulated interrupt requests.  The
synchronization will now run immediately after emulated interrupts are
disabled, which is where it belongs.

Signed-off-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Fixes: 04145a03db9d ("USB: UDC: Implement udc_async_callbacks in dummy-hcd")
Cc: stable &lt;stable@kernel.org&gt;
Link: https://patch.msgid.link/c7bc93fe-4241-4d04-bd56-27c12ba35c97@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>USB: dummy-hcd: Fix locking/synchronization error</title>
<updated>2026-03-18T15:16:29+00:00</updated>
<author>
<name>Alan Stern</name>
<email>stern@rowland.harvard.edu</email>
</author>
<published>2026-03-15T18:30:43+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=616a63ff495df12863692ab3f9f7b84e3fa7a66d'/>
<id>616a63ff495df12863692ab3f9f7b84e3fa7a66d</id>
<content type='text'>
Syzbot testing was able to provoke an addressing exception and crash
in the usb_gadget_udc_reset() routine in
drivers/usb/gadgets/udc/core.c, resulting from the fact that the
routine was called with a second ("driver") argument of NULL.  The bad
caller was set_link_state() in dummy_hcd.c, and the problem arose
because of a race between a USB reset and driver unbind.

These sorts of races were not supposed to be possible; commit
7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change"),
along with a few followup commits, was written specifically to prevent
them.  As it turns out, there are (at least) two errors remaining in
the code.  Another patch will address the second error; this one is
concerned with the first.

The error responsible for the syzbot crash occurred because the
stop_activity() routine will sometimes drop and then re-acquire the
dum-&gt;lock spinlock.  A call to stop_activity() occurs in
set_link_state() when handling an emulated USB reset, after the test
of dum-&gt;ints_enabled and before the increment of dum-&gt;callback_usage.
This allowed another thread (doing a driver unbind) to sneak in and
grab the spinlock, and then clear dum-&gt;ints_enabled and dum-&gt;driver.
Normally this other thread would have to wait for dum-&gt;callback_usage
to go down to 0 before it would clear dum-&gt;driver, but in this case it
didn't have to wait since dum-&gt;callback_usage had not yet been
incremented.

The fix is to increment dum-&gt;callback_usage _before_ calling
stop_activity() instead of after.  Then the thread doing the unbind
will not clear dum-&gt;driver until after the call to
usb_gadget_udc_reset() safely returns and dum-&gt;callback_usage has been
decremented again.

Signed-off-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Reported-by: syzbot+19bed92c97bee999e5db@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-usb/68fc7c9c.050a0220.346f24.023c.GAE@google.com/
Tested-by: syzbot+19bed92c97bee999e5db@syzkaller.appspotmail.com
Fixes: 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change")
Cc: stable &lt;stable@kernel.org&gt;
Link: https://patch.msgid.link/46135f42-fdbe-46b5-aac0-6ca70492af15@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Syzbot testing was able to provoke an addressing exception and crash
in the usb_gadget_udc_reset() routine in
drivers/usb/gadgets/udc/core.c, resulting from the fact that the
routine was called with a second ("driver") argument of NULL.  The bad
caller was set_link_state() in dummy_hcd.c, and the problem arose
because of a race between a USB reset and driver unbind.

These sorts of races were not supposed to be possible; commit
7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change"),
along with a few followup commits, was written specifically to prevent
them.  As it turns out, there are (at least) two errors remaining in
the code.  Another patch will address the second error; this one is
concerned with the first.

The error responsible for the syzbot crash occurred because the
stop_activity() routine will sometimes drop and then re-acquire the
dum-&gt;lock spinlock.  A call to stop_activity() occurs in
set_link_state() when handling an emulated USB reset, after the test
of dum-&gt;ints_enabled and before the increment of dum-&gt;callback_usage.
This allowed another thread (doing a driver unbind) to sneak in and
grab the spinlock, and then clear dum-&gt;ints_enabled and dum-&gt;driver.
Normally this other thread would have to wait for dum-&gt;callback_usage
to go down to 0 before it would clear dum-&gt;driver, but in this case it
didn't have to wait since dum-&gt;callback_usage had not yet been
incremented.

The fix is to increment dum-&gt;callback_usage _before_ calling
stop_activity() instead of after.  Then the thread doing the unbind
will not clear dum-&gt;driver until after the call to
usb_gadget_udc_reset() safely returns and dum-&gt;callback_usage has been
decremented again.

Signed-off-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Reported-by: syzbot+19bed92c97bee999e5db@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-usb/68fc7c9c.050a0220.346f24.023c.GAE@google.com/
Tested-by: syzbot+19bed92c97bee999e5db@syzkaller.appspotmail.com
Fixes: 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change")
Cc: stable &lt;stable@kernel.org&gt;
Link: https://patch.msgid.link/46135f42-fdbe-46b5-aac0-6ca70492af15@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
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