It is possible trigger below warning message from mass storage function,
------------[ cut here ]------------ WARNING: CPU: 6 PID: 3839 at drivers/usb/gadget/udc/core.c:294 usb_ep_queue+0x7c/0x104 CPU: 6 PID: 3839 Comm: file-storage Tainted: G S WC O 6.1.25-android14-11-g354e2a7e7cd9 #1 pstate: 22400005 (nzCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : usb_ep_queue+0x7c/0x104 lr : fsg_main_thread+0x494/0x1b3c
Root cause is mass storage function try to queue request from main thread, but other thread may already disable ep when function disable.
As mass storage function have record of ep enable/disable state, let's add the state check before queue request to UDC, it maybe avoid warning.
Also use common lock to protect ep state which avoid race between main thread and function disable.
Cc: stable@vger.kernel.org # 6.1 Signed-off-by: yuan linyu yuanlinyu@hihonor.com --- drivers/usb/gadget/function/f_mass_storage.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c index c265a1f62fc1..056083cb68cb 100644 --- a/drivers/usb/gadget/function/f_mass_storage.c +++ b/drivers/usb/gadget/function/f_mass_storage.c @@ -520,12 +520,25 @@ static int fsg_setup(struct usb_function *f, static int start_transfer(struct fsg_dev *fsg, struct usb_ep *ep, struct usb_request *req) { + unsigned long flags; int rc;
- if (ep == fsg->bulk_in) + spin_lock_irqsave(&fsg->common->lock, flags); + if (ep == fsg->bulk_in) { + if (!fsg->bulk_in_enabled) { + spin_unlock_irqrestore(&fsg->common->lock, flags); + return -ESHUTDOWN; + } dump_msg(fsg, "bulk-in", req->buf, req->length); + } else { + if (!fsg->bulk_out_enabled) { + spin_unlock_irqrestore(&fsg->common->lock, flags); + return -ESHUTDOWN; + } + }
rc = usb_ep_queue(ep, req, GFP_KERNEL); + spin_unlock_irqrestore(&fsg->common->lock, flags); if (rc) {
/* We can't do much more than wait for a reset */ @@ -2406,8 +2419,10 @@ static int fsg_set_alt(struct usb_function *f, unsigned intf, unsigned alt) static void fsg_disable(struct usb_function *f) { struct fsg_dev *fsg = fsg_from_func(f); + unsigned long flags;
/* Disable the endpoints */ + spin_lock_irqsave(&fsg->common->lock, flags); if (fsg->bulk_in_enabled) { usb_ep_disable(fsg->bulk_in); fsg->bulk_in_enabled = 0; @@ -2416,6 +2431,7 @@ static void fsg_disable(struct usb_function *f) usb_ep_disable(fsg->bulk_out); fsg->bulk_out_enabled = 0; } + spin_unlock_irqrestore(&fsg->common->lock, flags);
__raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE, NULL); }
Hi,
I am sorry, but this contains a major issue.
On 14.03.24 07:59, yuan linyu wrote:
It is possible trigger below warning message from mass storage function,
------------[ cut here ]------------ WARNING: CPU: 6 PID: 3839 at drivers/usb/gadget/udc/core.c:294 usb_ep_queue+0x7c/0x104 CPU: 6 PID: 3839 Comm: file-storage Tainted: G S WC O 6.1.25-android14-11-g354e2a7e7cd9 #1 pstate: 22400005 (nzCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : usb_ep_queue+0x7c/0x104 lr : fsg_main_thread+0x494/0x1b3c
Root cause is mass storage function try to queue request from main thread, but other thread may already disable ep when function disable.
As mass storage function have record of ep enable/disable state, let's add the state check before queue request to UDC, it maybe avoid warning.
Also use common lock to protect ep state which avoid race between main thread and function disable.
Cc: stable@vger.kernel.org # 6.1 Signed-off-by: yuan linyu yuanlinyu@hihonor.com
Nacked-by: Oliver Neukum oneukum@suse.com
drivers/usb/gadget/function/f_mass_storage.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c index c265a1f62fc1..056083cb68cb 100644 --- a/drivers/usb/gadget/function/f_mass_storage.c +++ b/drivers/usb/gadget/function/f_mass_storage.c @@ -520,12 +520,25 @@ static int fsg_setup(struct usb_function *f, static int start_transfer(struct fsg_dev *fsg, struct usb_ep *ep, struct usb_request *req) {
- unsigned long flags; int rc;
- if (ep == fsg->bulk_in)
- spin_lock_irqsave(&fsg->common->lock, flags);
Taking a spinlock.
- if (ep == fsg->bulk_in) {
if (!fsg->bulk_in_enabled) {spin_unlock_irqrestore(&fsg->common->lock, flags);return -ESHUTDOWN;}- } else {
if (!fsg->bulk_out_enabled) {spin_unlock_irqrestore(&fsg->common->lock, flags);return -ESHUTDOWN;}- }
rc = usb_ep_queue(ep, req, GFP_KERNEL);
This can sleep.
- spin_unlock_irqrestore(&fsg->common->lock, flags);
Giving up the lock.
Sorry, now for the longer explanation. You'd introduce a deadlock. You just cannot sleep with a spinlock held. It seems to me that if you want to do this cleanly, you need to revisit the locking to use locks you can sleep under.
HTH Oliver
From: Oliver Neukum oneukum@suse.com Sent: Thursday, March 14, 2024 3:54 PM To: yuanlinyu yuanlinyu@hihonor.com; Alan Stern stern@rowland.harvard.edu; Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org; stable@vger.kernel.org Subject: Re: [PATCH v1] usb: f_mass_storage: reduce chance to queue disable ep
Hi,
I am sorry, but this contains a major issue.
On 14.03.24 07:59, yuan linyu wrote:
It is possible trigger below warning message from mass storage function,
------------[ cut here ]------------ WARNING: CPU: 6 PID: 3839 at drivers/usb/gadget/udc/core.c:294
usb_ep_queue+0x7c/0x104
CPU: 6 PID: 3839 Comm: file-storage Tainted: G S WC O
6.1.25-android14-11-g354e2a7e7cd9 #1
pstate: 22400005 (nzCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : usb_ep_queue+0x7c/0x104 lr : fsg_main_thread+0x494/0x1b3c
Root cause is mass storage function try to queue request from main thread, but other thread may already disable ep when function disable.
As mass storage function have record of ep enable/disable state, let's add the state check before queue request to UDC, it maybe avoid warning.
Also use common lock to protect ep state which avoid race between main thread and function disable.
Cc: stable@vger.kernel.org # 6.1 Signed-off-by: yuan linyu yuanlinyu@hihonor.com
Nacked-by: Oliver Neukum oneukum@suse.com
drivers/usb/gadget/function/f_mass_storage.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/f_mass_storage.c
b/drivers/usb/gadget/function/f_mass_storage.c
index c265a1f62fc1..056083cb68cb 100644 --- a/drivers/usb/gadget/function/f_mass_storage.c +++ b/drivers/usb/gadget/function/f_mass_storage.c @@ -520,12 +520,25 @@ static int fsg_setup(struct usb_function *f, static int start_transfer(struct fsg_dev *fsg, struct usb_ep *ep, struct usb_request *req) {
- unsigned long flags; int rc;
- if (ep == fsg->bulk_in)
- spin_lock_irqsave(&fsg->common->lock, flags);
Taking a spinlock.
if (ep == fsg->bulk_in) {
if (!fsg->bulk_in_enabled) {spin_unlock_irqrestore(&fsg->common->lock, flags);return -ESHUTDOWN;}dump_msg(fsg, "bulk-in", req->buf, req->length);
} else {
if (!fsg->bulk_out_enabled) {spin_unlock_irqrestore(&fsg->common->lock, flags);return -ESHUTDOWN;}}
rc = usb_ep_queue(ep, req, GFP_KERNEL);
This can sleep.
- spin_unlock_irqrestore(&fsg->common->lock, flags);
Giving up the lock.
Sorry, now for the longer explanation. You'd introduce a deadlock. You just cannot sleep with a spinlock held. It seems to me that
I didn't review usb_ep_queue() clearly, in my test, I didn't hit sleep. But the concern is good, will find better way to avoid it.
if you want to do this cleanly, you need to revisit the locking to use locks you can sleep under.
HTH Oliver
From: yuanlinyu Sent: Thursday, March 14, 2024 4:14 PM To: 'Oliver Neukum' oneukum@suse.com; Alan Stern stern@rowland.harvard.edu; Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org; stable@vger.kernel.org Subject: RE: [PATCH v1] usb: f_mass_storage: reduce chance to queue disable ep
From: Oliver Neukum oneukum@suse.com Sent: Thursday, March 14, 2024 3:54 PM
Sorry, now for the longer explanation. You'd introduce a deadlock. You just cannot sleep with a spinlock held. It seems to me that
I didn't review usb_ep_queue() clearly, in my test, I didn't hit sleep. But the concern is good, will find better way to avoid it.
Oliver, could you share one example which can sleep ?
I check several UDC drivers, like dwc3, cdnsp, cdns3, Both disable/queue function have spinlock, this means no sleep, right ?
if you want to do this cleanly, you need to revisit the locking to use locks you can sleep under.
HTH Oliver
On Thu, Mar 14, 2024 at 02:59:49PM +0800, yuan linyu wrote:
It is possible trigger below warning message from mass storage function,
------------[ cut here ]------------ WARNING: CPU: 6 PID: 3839 at drivers/usb/gadget/udc/core.c:294 usb_ep_queue+0x7c/0x104 CPU: 6 PID: 3839 Comm: file-storage Tainted: G S WC O 6.1.25-android14-11-g354e2a7e7cd9 #1 pstate: 22400005 (nzCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : usb_ep_queue+0x7c/0x104 lr : fsg_main_thread+0x494/0x1b3c
Root cause is mass storage function try to queue request from main thread, but other thread may already disable ep when function disable.
As mass storage function have record of ep enable/disable state, let's add the state check before queue request to UDC, it maybe avoid warning.
Also use common lock to protect ep state which avoid race between main thread and function disable.
This seems like a lot of effort just to avoid a harmless WARNING. How about instead changing the WARNING to a debug-level message?
Alan Stern
Cc: stable@vger.kernel.org # 6.1 Signed-off-by: yuan linyu yuanlinyu@hihonor.com
drivers/usb/gadget/function/f_mass_storage.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c index c265a1f62fc1..056083cb68cb 100644 --- a/drivers/usb/gadget/function/f_mass_storage.c +++ b/drivers/usb/gadget/function/f_mass_storage.c @@ -520,12 +520,25 @@ static int fsg_setup(struct usb_function *f, static int start_transfer(struct fsg_dev *fsg, struct usb_ep *ep, struct usb_request *req) {
- unsigned long flags; int rc;
- if (ep == fsg->bulk_in)
- spin_lock_irqsave(&fsg->common->lock, flags);
- if (ep == fsg->bulk_in) {
if (!fsg->bulk_in_enabled) {spin_unlock_irqrestore(&fsg->common->lock, flags);return -ESHUTDOWN;}- } else {
if (!fsg->bulk_out_enabled) {spin_unlock_irqrestore(&fsg->common->lock, flags);return -ESHUTDOWN;}- }
rc = usb_ep_queue(ep, req, GFP_KERNEL);
- spin_unlock_irqrestore(&fsg->common->lock, flags); if (rc) {
/* We can't do much more than wait for a reset */ @@ -2406,8 +2419,10 @@ static int fsg_set_alt(struct usb_function *f, unsigned intf, unsigned alt) static void fsg_disable(struct usb_function *f) { struct fsg_dev *fsg = fsg_from_func(f);
- unsigned long flags;
/* Disable the endpoints */
- spin_lock_irqsave(&fsg->common->lock, flags); if (fsg->bulk_in_enabled) { usb_ep_disable(fsg->bulk_in); fsg->bulk_in_enabled = 0;
@@ -2416,6 +2431,7 @@ static void fsg_disable(struct usb_function *f) usb_ep_disable(fsg->bulk_out); fsg->bulk_out_enabled = 0; }
- spin_unlock_irqrestore(&fsg->common->lock, flags);
__raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE, NULL); } -- 2.25.1
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