* [PATCH v4 1/2] USB: cdc-acm: fix close_delay and closing_wait units in TIOCSSERIAL
@ 2020-03-12 13:31 Anthony Mallet
2020-03-12 13:31 ` [PATCH v4 2/2] USB: cdc-acm: fix rounding error " Anthony Mallet
0 siblings, 1 reply; 4+ messages in thread
From: Anthony Mallet @ 2020-03-12 13:31 UTC (permalink / raw)
To: Oliver Neukum, linux-usb; +Cc: Anthony Mallet
close_delay and closing_wait are specified in hundredth of a second but stored
internally in jiffies. Use the jiffies_to_msecs() and msecs_to_jiffies()
functions to convert from each other.
Signed-off-by: Anthony Mallet <anthony.mallet@laas.fr>
---
Changed in v2: none
Changed in v3: version this patch series
Changes in v4: none (diffed against e6e6ec4 from github.com/torvalds/linux.git)
---
drivers/usb/class/cdc-acm.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 62f4fb9b362f..da619176deca 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -896,10 +896,10 @@ static int get_serial_info(struct tty_struct *tty, struct serial_struct *ss)
ss->xmit_fifo_size = acm->writesize;
ss->baud_base = le32_to_cpu(acm->line.dwDTERate);
- ss->close_delay = acm->port.close_delay / 10;
+ ss->close_delay = jiffies_to_msecs(acm->port.close_delay) / 10;
ss->closing_wait = acm->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
ASYNC_CLOSING_WAIT_NONE :
- acm->port.closing_wait / 10;
+ jiffies_to_msecs(acm->port.closing_wait) / 10;
return 0;
}
@@ -909,9 +909,10 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
unsigned int closing_wait, close_delay;
int retval = 0;
- close_delay = ss->close_delay * 10;
+ close_delay = msecs_to_jiffies(ss->close_delay * 10);
closing_wait = ss->closing_wait == ASYNC_CLOSING_WAIT_NONE ?
- ASYNC_CLOSING_WAIT_NONE : ss->closing_wait * 10;
+ ASYNC_CLOSING_WAIT_NONE :
+ msecs_to_jiffies(ss->closing_wait * 10);
mutex_lock(&acm->port.mutex);
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v4 2/2] USB: cdc-acm: fix rounding error in TIOCSSERIAL
2020-03-12 13:31 [PATCH v4 1/2] USB: cdc-acm: fix close_delay and closing_wait units in TIOCSSERIAL Anthony Mallet
@ 2020-03-12 13:31 ` Anthony Mallet
2020-03-27 12:37 ` Matthias Reichl
0 siblings, 1 reply; 4+ messages in thread
From: Anthony Mallet @ 2020-03-12 13:31 UTC (permalink / raw)
To: Oliver Neukum, linux-usb; +Cc: Anthony Mallet
By default, tty_port_init() initializes those parameters to a multiple
of HZ. For instance in line 69 of tty_port.c:
port->close_delay = (50 * HZ) / 100;
https://github.com/torvalds/linux/blob/master/drivers/tty/tty_port.c#L69
With e.g. CONFIG_HZ = 250 (as this is the case for Ubuntu 18.04
linux-image-4.15.0-37-generic), the default setting for close_delay is
thus 125.
When ioctl(fd, TIOCGSERIAL, &s) is executed, the setting returned in
user space is '12' (125/10). When ioctl(fd, TIOCSSERIAL, &s) is then
executed with the same setting '12', the value is interpreted as '120'
which is different from the current setting and a EPERM error may be
raised by set_serial_info() if !CAP_SYS_ADMIN.
https://github.com/torvalds/linux/blob/master/drivers/usb/class/cdc-acm.c#L919
Fixes: ba2d8ce9db0a6 ("cdc-acm: implement TIOCSSERIAL to avoid blocking close(2)")
Signed-off-by: Anthony Mallet <anthony.mallet@laas.fr>
---
Changed in v2: fix typo (extra closing brace)
Changed in v3: version this patch series
Changed in v4: diffed against e6e6ec4 from github.com/torvalds/linux.git
---
drivers/usb/class/cdc-acm.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index da619176deca..a41a3d27016c 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -907,6 +907,7 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
{
struct acm *acm = tty->driver_data;
unsigned int closing_wait, close_delay;
+ unsigned int old_closing_wait, old_close_delay;
int retval = 0;
close_delay = msecs_to_jiffies(ss->close_delay * 10);
@@ -914,18 +915,24 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
ASYNC_CLOSING_WAIT_NONE :
msecs_to_jiffies(ss->closing_wait * 10);
+ /* we must redo the rounding here, so that the values match */
+ old_close_delay = jiffies_to_msecs(acm->port.close_delay) / 10;
+ old_closing_wait = acm->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
+ ASYNC_CLOSING_WAIT_NONE :
+ jiffies_to_msecs(acm->port.closing_wait) / 10;
+
mutex_lock(&acm->port.mutex);
- if (!capable(CAP_SYS_ADMIN)) {
- if ((close_delay != acm->port.close_delay) ||
- (closing_wait != acm->port.closing_wait))
+ if ((ss->close_delay != old_close_delay) ||
+ (ss->closing_wait != old_closing_wait)) {
+ if (!capable(CAP_SYS_ADMIN))
retval = -EPERM;
- else
- retval = -EOPNOTSUPP;
- } else {
- acm->port.close_delay = close_delay;
- acm->port.closing_wait = closing_wait;
- }
+ else {
+ acm->port.close_delay = close_delay;
+ acm->port.closing_wait = closing_wait;
+ }
+ } else
+ retval = -EOPNOTSUPP;
mutex_unlock(&acm->port.mutex);
return retval;
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v4 2/2] USB: cdc-acm: fix rounding error in TIOCSSERIAL
2020-03-12 13:31 ` [PATCH v4 2/2] USB: cdc-acm: fix rounding error " Anthony Mallet
@ 2020-03-27 12:37 ` Matthias Reichl
2020-03-27 12:53 ` Greg Kroah-Hartman
0 siblings, 1 reply; 4+ messages in thread
From: Matthias Reichl @ 2020-03-27 12:37 UTC (permalink / raw)
To: Anthony Mallet, Greg Kroah-Hartman; +Cc: Oliver Neukum, linux-usb
On Thu, Mar 12, 2020 at 02:31:01PM +0100, Anthony Mallet wrote:
> By default, tty_port_init() initializes those parameters to a multiple
> of HZ. For instance in line 69 of tty_port.c:
> port->close_delay = (50 * HZ) / 100;
> https://github.com/torvalds/linux/blob/master/drivers/tty/tty_port.c#L69
>
> With e.g. CONFIG_HZ = 250 (as this is the case for Ubuntu 18.04
> linux-image-4.15.0-37-generic), the default setting for close_delay is
> thus 125.
>
> When ioctl(fd, TIOCGSERIAL, &s) is executed, the setting returned in
> user space is '12' (125/10). When ioctl(fd, TIOCSSERIAL, &s) is then
> executed with the same setting '12', the value is interpreted as '120'
> which is different from the current setting and a EPERM error may be
> raised by set_serial_info() if !CAP_SYS_ADMIN.
> https://github.com/torvalds/linux/blob/master/drivers/usb/class/cdc-acm.c#L919
>
> Fixes: ba2d8ce9db0a6 ("cdc-acm: implement TIOCSSERIAL to avoid blocking close(2)")
> Signed-off-by: Anthony Mallet <anthony.mallet@laas.fr>
> ---
> Changed in v2: fix typo (extra closing brace)
> Changed in v3: version this patch series
> Changed in v4: diffed against e6e6ec4 from github.com/torvalds/linux.git
> ---
> drivers/usb/class/cdc-acm.c | 27 +++++++++++++++++----------
> 1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
> index da619176deca..a41a3d27016c 100644
> --- a/drivers/usb/class/cdc-acm.c
> +++ b/drivers/usb/class/cdc-acm.c
> @@ -907,6 +907,7 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
> {
> struct acm *acm = tty->driver_data;
> unsigned int closing_wait, close_delay;
> + unsigned int old_closing_wait, old_close_delay;
> int retval = 0;
>
> close_delay = msecs_to_jiffies(ss->close_delay * 10);
> @@ -914,18 +915,24 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
> ASYNC_CLOSING_WAIT_NONE :
> msecs_to_jiffies(ss->closing_wait * 10);
>
> + /* we must redo the rounding here, so that the values match */
> + old_close_delay = jiffies_to_msecs(acm->port.close_delay) / 10;
> + old_closing_wait = acm->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
> + ASYNC_CLOSING_WAIT_NONE :
> + jiffies_to_msecs(acm->port.closing_wait) / 10;
> +
> mutex_lock(&acm->port.mutex);
>
> - if (!capable(CAP_SYS_ADMIN)) {
> - if ((close_delay != acm->port.close_delay) ||
> - (closing_wait != acm->port.closing_wait))
> + if ((ss->close_delay != old_close_delay) ||
> + (ss->closing_wait != old_closing_wait)) {
> + if (!capable(CAP_SYS_ADMIN))
> retval = -EPERM;
> - else
> - retval = -EOPNOTSUPP;
> - } else {
> - acm->port.close_delay = close_delay;
> - acm->port.closing_wait = closing_wait;
> - }
> + else {
> + acm->port.close_delay = close_delay;
> + acm->port.closing_wait = closing_wait;
> + }
> + } else
> + retval = -EOPNOTSUPP;
Swapping the order of the capability / close settings checks introduced
a rather unexpected regression: when running with CAP_SYS_ADMIN we now
get -EOPNOTSUPP when the close settings are unchanged.
This will break programs / scripts that set these settings to fixed
values.
eg (tested on vanilla 5.4.28) changing the settings works, but
setting the same value again fails:
# setserial -a /dev/ttyACM0
/dev/ttyACM0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0
Baud_base: 9600, close_delay: 50, divisor: 0
closing_wait: 3000
Flags: spd_normal
# setserial /dev/ttyACM0 closing_wait 2000
# setserial /dev/ttyACM0 closing_wait 2000
Cannot set serial info: Operation not supported
From the commit message it's not clear why this behaviour was changed
so I suspect this might be a bug.
so long,
Hias
>
> mutex_unlock(&acm->port.mutex);
> return retval;
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v4 2/2] USB: cdc-acm: fix rounding error in TIOCSSERIAL
2020-03-27 12:37 ` Matthias Reichl
@ 2020-03-27 12:53 ` Greg Kroah-Hartman
0 siblings, 0 replies; 4+ messages in thread
From: Greg Kroah-Hartman @ 2020-03-27 12:53 UTC (permalink / raw)
To: Matthias Reichl; +Cc: Anthony Mallet, Oliver Neukum, linux-usb
On Fri, Mar 27, 2020 at 01:37:24PM +0100, Matthias Reichl wrote:
> On Thu, Mar 12, 2020 at 02:31:01PM +0100, Anthony Mallet wrote:
> > By default, tty_port_init() initializes those parameters to a multiple
> > of HZ. For instance in line 69 of tty_port.c:
> > port->close_delay = (50 * HZ) / 100;
> > https://github.com/torvalds/linux/blob/master/drivers/tty/tty_port.c#L69
> >
> > With e.g. CONFIG_HZ = 250 (as this is the case for Ubuntu 18.04
> > linux-image-4.15.0-37-generic), the default setting for close_delay is
> > thus 125.
> >
> > When ioctl(fd, TIOCGSERIAL, &s) is executed, the setting returned in
> > user space is '12' (125/10). When ioctl(fd, TIOCSSERIAL, &s) is then
> > executed with the same setting '12', the value is interpreted as '120'
> > which is different from the current setting and a EPERM error may be
> > raised by set_serial_info() if !CAP_SYS_ADMIN.
> > https://github.com/torvalds/linux/blob/master/drivers/usb/class/cdc-acm.c#L919
> >
> > Fixes: ba2d8ce9db0a6 ("cdc-acm: implement TIOCSSERIAL to avoid blocking close(2)")
> > Signed-off-by: Anthony Mallet <anthony.mallet@laas.fr>
> > ---
> > Changed in v2: fix typo (extra closing brace)
> > Changed in v3: version this patch series
> > Changed in v4: diffed against e6e6ec4 from github.com/torvalds/linux.git
> > ---
> > drivers/usb/class/cdc-acm.c | 27 +++++++++++++++++----------
> > 1 file changed, 17 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
> > index da619176deca..a41a3d27016c 100644
> > --- a/drivers/usb/class/cdc-acm.c
> > +++ b/drivers/usb/class/cdc-acm.c
> > @@ -907,6 +907,7 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
> > {
> > struct acm *acm = tty->driver_data;
> > unsigned int closing_wait, close_delay;
> > + unsigned int old_closing_wait, old_close_delay;
> > int retval = 0;
> >
> > close_delay = msecs_to_jiffies(ss->close_delay * 10);
> > @@ -914,18 +915,24 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
> > ASYNC_CLOSING_WAIT_NONE :
> > msecs_to_jiffies(ss->closing_wait * 10);
> >
> > + /* we must redo the rounding here, so that the values match */
> > + old_close_delay = jiffies_to_msecs(acm->port.close_delay) / 10;
> > + old_closing_wait = acm->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
> > + ASYNC_CLOSING_WAIT_NONE :
> > + jiffies_to_msecs(acm->port.closing_wait) / 10;
> > +
> > mutex_lock(&acm->port.mutex);
> >
> > - if (!capable(CAP_SYS_ADMIN)) {
> > - if ((close_delay != acm->port.close_delay) ||
> > - (closing_wait != acm->port.closing_wait))
> > + if ((ss->close_delay != old_close_delay) ||
> > + (ss->closing_wait != old_closing_wait)) {
> > + if (!capable(CAP_SYS_ADMIN))
> > retval = -EPERM;
> > - else
> > - retval = -EOPNOTSUPP;
> > - } else {
> > - acm->port.close_delay = close_delay;
> > - acm->port.closing_wait = closing_wait;
> > - }
> > + else {
> > + acm->port.close_delay = close_delay;
> > + acm->port.closing_wait = closing_wait;
> > + }
> > + } else
> > + retval = -EOPNOTSUPP;
>
> Swapping the order of the capability / close settings checks introduced
> a rather unexpected regression: when running with CAP_SYS_ADMIN we now
> get -EOPNOTSUPP when the close settings are unchanged.
>
> This will break programs / scripts that set these settings to fixed
> values.
>
> eg (tested on vanilla 5.4.28) changing the settings works, but
> setting the same value again fails:
>
> # setserial -a /dev/ttyACM0
> /dev/ttyACM0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0
> Baud_base: 9600, close_delay: 50, divisor: 0
> closing_wait: 3000
> Flags: spd_normal
>
> # setserial /dev/ttyACM0 closing_wait 2000
> # setserial /dev/ttyACM0 closing_wait 2000
> Cannot set serial info: Operation not supported
>
> >From the commit message it's not clear why this behaviour was changed
> so I suspect this might be a bug.
Looks like a bug :(
Care to send a patch to fix this up?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-03-12 13:31 [PATCH v4 1/2] USB: cdc-acm: fix close_delay and closing_wait units in TIOCSSERIAL Anthony Mallet
2020-03-12 13:31 ` [PATCH v4 2/2] USB: cdc-acm: fix rounding error " Anthony Mallet
2020-03-27 12:37 ` Matthias Reichl
2020-03-27 12:53 ` Greg Kroah-Hartman
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