@@ -1,4 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
+
+CAPABILITY_ANALYSIS := y
+
obj-$(CONFIG_TTY) += tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \
tty_buffer.o tty_port.o tty_mutex.o \
tty_ldsem.o tty_baudrate.o tty_jobctrl.o \
@@ -1088,6 +1088,7 @@ static void __isig(int sig, struct tty_struct *tty)
* Locking: %ctrl.lock
*/
static void isig(int sig, struct tty_struct *tty)
+ __must_hold_shared(&tty->termios_rwsem)
{
struct n_tty_data *ldata = tty->disc_data;
@@ -1135,6 +1136,7 @@ static void isig(int sig, struct tty_struct *tty)
* Note: may get exclusive %termios_rwsem if flushing input buffer
*/
static void n_tty_receive_break(struct tty_struct *tty)
+ __must_hold_shared(&tty->termios_rwsem)
{
struct n_tty_data *ldata = tty->disc_data;
@@ -1204,6 +1206,7 @@ static void n_tty_receive_parity_error(const struct tty_struct *tty,
static void
n_tty_receive_signal_char(struct tty_struct *tty, int signal, u8 c)
+ __must_hold_shared(&tty->termios_rwsem)
{
isig(signal, tty);
if (I_IXON(tty))
@@ -1353,6 +1356,7 @@ static bool n_tty_receive_char_canon(struct tty_struct *tty, u8 c)
static void n_tty_receive_char_special(struct tty_struct *tty, u8 c,
bool lookahead_done)
+ __must_hold_shared(&tty->termios_rwsem)
{
struct n_tty_data *ldata = tty->disc_data;
@@ -1463,6 +1467,7 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, u8 c,
static void
n_tty_receive_char_flagged(struct tty_struct *tty, u8 c, u8 flag)
+ __must_hold_shared(&tty->termios_rwsem)
{
switch (flag) {
case TTY_BREAK:
@@ -1483,6 +1488,7 @@ n_tty_receive_char_flagged(struct tty_struct *tty, u8 c, u8 flag)
static void
n_tty_receive_char_lnext(struct tty_struct *tty, u8 c, u8 flag)
+ __must_hold_shared(&tty->termios_rwsem)
{
struct n_tty_data *ldata = tty->disc_data;
@@ -1540,6 +1546,7 @@ n_tty_receive_buf_real_raw(const struct tty_struct *tty, const u8 *cp,
static void
n_tty_receive_buf_raw(struct tty_struct *tty, const u8 *cp, const u8 *fp,
size_t count)
+ __must_hold_shared(&tty->termios_rwsem)
{
struct n_tty_data *ldata = tty->disc_data;
u8 flag = TTY_NORMAL;
@@ -1571,6 +1578,7 @@ n_tty_receive_buf_closing(struct tty_struct *tty, const u8 *cp, const u8 *fp,
static void n_tty_receive_buf_standard(struct tty_struct *tty, const u8 *cp,
const u8 *fp, size_t count,
bool lookahead_done)
+ __must_hold_shared(&tty->termios_rwsem)
{
struct n_tty_data *ldata = tty->disc_data;
u8 flag = TTY_NORMAL;
@@ -1609,6 +1617,7 @@ static void n_tty_receive_buf_standard(struct tty_struct *tty, const u8 *cp,
static void __receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp,
size_t count)
+ __must_hold_shared(&tty->termios_rwsem)
{
struct n_tty_data *ldata = tty->disc_data;
bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
@@ -2188,6 +2197,10 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
return kb - kbuf;
}
+ /* Adopted locks from prior call. */
+ __acquire(&ldata->atomic_read_lock);
+ __acquire_shared(&tty->termios_rwsem);
+
/* No more data - release locks and stop retries */
n_tty_kick_worker(tty);
n_tty_check_unthrottle(tty);
@@ -2305,6 +2318,9 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
more_to_be_read:
remove_wait_queue(&tty->read_wait, &wait);
*cookie = cookie;
+ /* Hand-off locks to retry with cookie set. */
+ __release_shared(&tty->termios_rwsem);
+ __release(&ldata->atomic_read_lock);
return kb - kbuf;
}
}
@@ -824,6 +824,7 @@ static int ptmx_open(struct inode *inode, struct file *filp)
tty = tty_init_dev(ptm_driver, index);
/* The tty returned here is locked so we can safely
drop the mutex */
+ lockdep_assert_held(&tty->legacy_mutex);
mutex_unlock(&tty_mutex);
retval = PTR_ERR(tty);
@@ -149,6 +149,7 @@ static const struct sysrq_key_op sysrq_unraw_op = {
static void sysrq_handle_crash(u8 key)
{
/* release the RCU read lock before crashing */
+ lockdep_assert_in_rcu_read_lock();
rcu_read_unlock();
panic("sysrq triggered crash\n");
@@ -60,15 +60,15 @@ static inline void tty_set_flow_change(struct tty_struct *tty,
smp_mb();
}
-int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout);
-void tty_ldisc_unlock(struct tty_struct *tty);
+int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) __cond_acquires(0, &tty->ldisc_sem);
+void tty_ldisc_unlock(struct tty_struct *tty) __releases(&tty->ldisc_sem);
int __tty_check_change(struct tty_struct *tty, int sig);
int tty_check_change(struct tty_struct *tty);
void __stop_tty(struct tty_struct *tty);
void __start_tty(struct tty_struct *tty);
-void tty_write_unlock(struct tty_struct *tty);
-int tty_write_lock(struct tty_struct *tty, bool ndelay);
+void tty_write_unlock(struct tty_struct *tty) __releases(&tty->atomic_write_lock);
+int tty_write_lock(struct tty_struct *tty, bool ndelay) __cond_acquires(0, &tty->atomic_write_lock);
void tty_vhangup_session(struct tty_struct *tty);
void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty);
int tty_signal_session_leader(struct tty_struct *tty, int exit_session);
@@ -52,10 +52,8 @@
*/
void tty_buffer_lock_exclusive(struct tty_port *port)
{
- struct tty_bufhead *buf = &port->buf;
-
- atomic_inc(&buf->priority);
- mutex_lock(&buf->lock);
+ atomic_inc(&port->buf.priority);
+ mutex_lock(&port->buf.lock);
}
EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
@@ -73,7 +71,7 @@ void tty_buffer_unlock_exclusive(struct tty_port *port)
bool restart = buf->head->commit != buf->head->read;
atomic_dec(&buf->priority);
- mutex_unlock(&buf->lock);
+ mutex_unlock(&port->buf.lock);
if (restart)
queue_work(system_unbound_wq, &buf->work);
@@ -167,6 +167,7 @@ static void release_tty(struct tty_struct *tty, int idx);
* Locking: none. Must be called after tty is definitely unused
*/
static void free_tty_struct(struct tty_struct *tty)
+ __capability_unsafe(/* destructor */)
{
tty_ldisc_deinit(tty);
put_device(tty->dev);
@@ -965,7 +966,7 @@ static ssize_t iterate_tty_write(struct tty_ldisc *ld, struct tty_struct *tty,
ssize_t ret, written = 0;
ret = tty_write_lock(tty, file->f_flags & O_NDELAY);
- if (ret < 0)
+ if (ret)
return ret;
/*
@@ -1154,7 +1155,7 @@ int tty_send_xchar(struct tty_struct *tty, u8 ch)
return 0;
}
- if (tty_write_lock(tty, false) < 0)
+ if (tty_write_lock(tty, false))
return -ERESTARTSYS;
down_read(&tty->termios_rwsem);
@@ -1391,6 +1392,7 @@ static int tty_reopen(struct tty_struct *tty)
* Return: new tty structure
*/
struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
+ __capability_unsafe(/* returns with locked tty */)
{
struct tty_struct *tty;
int retval;
@@ -1874,6 +1876,7 @@ int tty_release(struct inode *inode, struct file *filp)
* will not work then. It expects inodes to be from devpts FS.
*/
static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
+ __capability_unsafe(/* returns with locked tty */)
{
struct tty_struct *tty;
int retval;
@@ -2037,6 +2040,7 @@ EXPORT_SYMBOL_GPL(tty_kopen_shared);
*/
static struct tty_struct *tty_open_by_driver(dev_t device,
struct file *filp)
+ __capability_unsafe(/* returns with locked tty */)
{
struct tty_struct *tty;
struct tty_driver *driver = NULL;
@@ -2137,6 +2141,8 @@ static int tty_open(struct inode *inode, struct file *filp)
goto retry_open;
}
+ lockdep_assert_held(&tty->legacy_mutex);
+
tty_add_file(tty, filp);
check_tty_count(tty, __func__);
@@ -2486,7 +2492,7 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
return tty->ops->break_ctl(tty, duration);
/* Do the work ourselves */
- if (tty_write_lock(tty, false) < 0)
+ if (tty_write_lock(tty, false))
return -EINTR;
retval = tty->ops->break_ctl(tty, -1);
@@ -489,7 +489,7 @@ static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
if (retval < 0)
return retval;
- if (tty_write_lock(tty, false) < 0)
+ if (tty_write_lock(tty, false))
goto retry_write_wait;
/* Racing writer? */
@@ -237,6 +237,7 @@ const struct seq_operations tty_ldiscs_seq_ops = {
* to wait for any ldisc lifetime events to finish.
*/
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
+ __cond_acquires_shared(nonnull, &tty->ldisc_sem)
{
struct tty_ldisc *ld;
@@ -257,6 +258,7 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
* and timer functions.
*/
struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
+ __cond_acquires_shared(nonnull, &tty->ldisc_sem)
{
struct tty_ldisc *ld = NULL;
@@ -277,26 +279,43 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref);
* in IRQ context.
*/
void tty_ldisc_deref(struct tty_ldisc *ld)
+ __releases_shared(&ld->tty->ldisc_sem)
{
ldsem_up_read(&ld->tty->ldisc_sem);
}
EXPORT_SYMBOL_GPL(tty_ldisc_deref);
+/*
+ * Note: Capability analysis does not like asymmetric interfaces (above types
+ * for ref and deref are tty_struct and tty_ldisc respectively -- which are
+ * dependent, but the compiler cannot figure that out); in this case, work
+ * around that with this helper which takes an unused @tty argument but tells
+ * the analysis which lock is released.
+ */
+static inline void __tty_ldisc_deref(struct tty_struct *tty, struct tty_ldisc *ld)
+ __releases_shared(&tty->ldisc_sem)
+ __capability_unsafe(/* matches released with tty_ldisc_ref() */)
+{
+ tty_ldisc_deref(ld);
+}
static inline int
__tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
+ __cond_acquires(true, &tty->ldisc_sem)
{
return ldsem_down_write(&tty->ldisc_sem, timeout);
}
static inline int
__tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout)
+ __cond_acquires(true, &tty->ldisc_sem)
{
return ldsem_down_write_nested(&tty->ldisc_sem,
LDISC_SEM_OTHER, timeout);
}
static inline void __tty_ldisc_unlock(struct tty_struct *tty)
+ __releases(&tty->ldisc_sem)
{
ldsem_up_write(&tty->ldisc_sem);
}
@@ -328,6 +347,8 @@ void tty_ldisc_unlock(struct tty_struct *tty)
static int
tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
unsigned long timeout)
+ __cond_acquires(0, &tty->ldisc_sem)
+ __cond_acquires(0, &tty2->ldisc_sem)
{
int ret;
@@ -362,16 +383,23 @@ tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
}
static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
+ __acquires(&tty->ldisc_sem)
+ __acquires(&tty2->ldisc_sem)
+ __capability_unsafe(/* MAX_SCHEDULE_TIMEOUT ensures acquisition */)
{
tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT);
}
static void tty_ldisc_unlock_pair(struct tty_struct *tty,
struct tty_struct *tty2)
+ __releases(&tty->ldisc_sem)
+ __releases(&tty2->ldisc_sem)
{
__tty_ldisc_unlock(tty);
if (tty2)
__tty_ldisc_unlock(tty2);
+ else
+ __release(&tty2->ldisc_sem);
}
/**
@@ -387,7 +415,7 @@ void tty_ldisc_flush(struct tty_struct *tty)
tty_buffer_flush(tty, ld);
if (ld)
- tty_ldisc_deref(ld);
+ __tty_ldisc_deref(tty, ld);
}
EXPORT_SYMBOL_GPL(tty_ldisc_flush);
@@ -694,7 +722,7 @@ void tty_ldisc_hangup(struct tty_struct *tty, bool reinit)
tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc);
ld = tty_ldisc_ref(tty);
- if (ld != NULL) {
+ if (ld) {
if (ld->ops->flush_buffer)
ld->ops->flush_buffer(tty);
tty_driver_flush_buffer(tty);
@@ -703,7 +731,7 @@ void tty_ldisc_hangup(struct tty_struct *tty, bool reinit)
ld->ops->write_wakeup(tty);
if (ld->ops->hangup)
ld->ops->hangup(tty);
- tty_ldisc_deref(ld);
+ __tty_ldisc_deref(tty, ld);
}
wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
@@ -716,6 +744,7 @@ void tty_ldisc_hangup(struct tty_struct *tty, bool reinit)
* Avoid racing set_ldisc or tty_ldisc_release
*/
tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT);
+ lockdep_assert_held_write(&tty->ldisc_sem);
if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
tty_reset_termios(tty);
@@ -390,6 +390,7 @@ void ldsem_up_read(struct ld_semaphore *sem)
{
long count;
+ __release_shared(sem);
rwsem_release(&sem->dep_map, _RET_IP_);
count = atomic_long_add_return(-LDSEM_READ_BIAS, &sem->count);
@@ -404,6 +405,7 @@ void ldsem_up_write(struct ld_semaphore *sem)
{
long count;
+ __release(sem);
rwsem_release(&sem->dep_map, _RET_IP_);
count = atomic_long_add_return(-LDSEM_WRITE_BIAS, &sem->count);
@@ -41,12 +41,16 @@ void tty_lock_slave(struct tty_struct *tty)
{
if (tty && tty != tty->link)
tty_lock(tty);
+ else
+ __acquire(&tty->legacy_mutex);
}
void tty_unlock_slave(struct tty_struct *tty)
{
if (tty && tty != tty->link)
tty_unlock(tty);
+ else
+ __release(&tty->legacy_mutex);
}
void tty_set_lock_subclass(struct tty_struct *tty)
@@ -509,6 +509,7 @@ EXPORT_SYMBOL(tty_port_lower_dtr_rts);
*/
int tty_port_block_til_ready(struct tty_port *port,
struct tty_struct *tty, struct file *filp)
+ __must_hold(&tty->legacy_mutex)
{
int do_clocal = 0, retval;
unsigned long flags;
@@ -764,6 +765,7 @@ EXPORT_SYMBOL_GPL(tty_port_install);
*/
int tty_port_open(struct tty_port *port, struct tty_struct *tty,
struct file *filp)
+ __must_hold(&tty->legacy_mutex)
{
spin_lock_irq(&port->lock);
++port->count;
@@ -234,8 +234,8 @@ struct tty_struct {
void *disc_data;
void *driver_data;
spinlock_t files_lock;
- int write_cnt;
- u8 *write_buf;
+ int write_cnt __guarded_by(&atomic_write_lock);
+ u8 *write_buf __guarded_by(&atomic_write_lock);
struct list_head tty_files;
@@ -500,11 +500,11 @@ long vt_compat_ioctl(struct tty_struct *tty, unsigned int cmd,
/* tty_mutex.c */
/* functions for preparation of BKL removal */
-void tty_lock(struct tty_struct *tty);
-int tty_lock_interruptible(struct tty_struct *tty);
-void tty_unlock(struct tty_struct *tty);
-void tty_lock_slave(struct tty_struct *tty);
-void tty_unlock_slave(struct tty_struct *tty);
+void tty_lock(struct tty_struct *tty) __acquires(&tty->legacy_mutex);
+int tty_lock_interruptible(struct tty_struct *tty) __cond_acquires(0, &tty->legacy_mutex);
+void tty_unlock(struct tty_struct *tty) __releases(&tty->legacy_mutex);
+void tty_lock_slave(struct tty_struct *tty) __acquires(&tty->legacy_mutex);
+void tty_unlock_slave(struct tty_struct *tty) __releases(&tty->legacy_mutex);
void tty_set_lock_subclass(struct tty_struct *tty);
#endif
@@ -86,7 +86,7 @@ static inline size_t tty_insert_flip_string(struct tty_port *port,
size_t tty_ldisc_receive_buf(struct tty_ldisc *ld, const u8 *p, const u8 *f,
size_t count);
-void tty_buffer_lock_exclusive(struct tty_port *port);
-void tty_buffer_unlock_exclusive(struct tty_port *port);
+void tty_buffer_lock_exclusive(struct tty_port *port) __acquires(&port->buf.lock);
+void tty_buffer_unlock_exclusive(struct tty_port *port) __releases(&port->buf.lock);
#endif /* _LINUX_TTY_FLIP_H */
@@ -14,7 +14,7 @@ struct tty_struct;
/*
* the semaphore definition
*/
-struct ld_semaphore {
+struct_with_capability(ld_semaphore) {
atomic_long_t count;
raw_spinlock_t wait_lock;
unsigned int wait_readers;
@@ -33,21 +33,22 @@ do { \
static struct lock_class_key __key; \
\
__init_ldsem((sem), #sem, &__key); \
+ __assert_cap(sem); \
} while (0)
-int ldsem_down_read(struct ld_semaphore *sem, long timeout);
-int ldsem_down_read_trylock(struct ld_semaphore *sem);
-int ldsem_down_write(struct ld_semaphore *sem, long timeout);
-int ldsem_down_write_trylock(struct ld_semaphore *sem);
-void ldsem_up_read(struct ld_semaphore *sem);
-void ldsem_up_write(struct ld_semaphore *sem);
+int ldsem_down_read(struct ld_semaphore *sem, long timeout) __cond_acquires_shared(true, sem);
+int ldsem_down_read_trylock(struct ld_semaphore *sem) __cond_acquires_shared(true, sem);
+int ldsem_down_write(struct ld_semaphore *sem, long timeout) __cond_acquires(true, sem);
+int ldsem_down_write_trylock(struct ld_semaphore *sem) __cond_acquires(true, sem);
+void ldsem_up_read(struct ld_semaphore *sem) __releases_shared(sem);
+void ldsem_up_write(struct ld_semaphore *sem) __releases(sem);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
- long timeout);
+ long timeout) __cond_acquires_shared(true, sem);
int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
- long timeout);
+ long timeout) __cond_acquires(true, sem);
#else
# define ldsem_down_read_nested(sem, subclass, timeout) \
ldsem_down_read(sem, timeout)
Enable capability analysis for drivers/tty/*. This demonstrates a larger conversion to use Clang's capability analysis. The benefit is additional static checking of locking rules, along with better documentation. Signed-off-by: Marco Elver <elver@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jirislaby@kernel.org> --- v2: * New patch. --- drivers/tty/Makefile | 3 +++ drivers/tty/n_tty.c | 16 ++++++++++++++++ drivers/tty/pty.c | 1 + drivers/tty/sysrq.c | 1 + drivers/tty/tty.h | 8 ++++---- drivers/tty/tty_buffer.c | 8 +++----- drivers/tty/tty_io.c | 12 +++++++++--- drivers/tty/tty_ioctl.c | 2 +- drivers/tty/tty_ldisc.c | 35 ++++++++++++++++++++++++++++++++--- drivers/tty/tty_ldsem.c | 2 ++ drivers/tty/tty_mutex.c | 4 ++++ drivers/tty/tty_port.c | 2 ++ include/linux/tty.h | 14 +++++++------- include/linux/tty_flip.h | 4 ++-- include/linux/tty_ldisc.h | 19 ++++++++++--------- 15 files changed, 97 insertions(+), 34 deletions(-)