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Subjectnet/3com/3c515: Fix timer handling, prevent leaks and crashes
The timer handling in this driver is broken in several ways:

- corkscrew_open() initializes and arms a timer before requesting the
device interrupt. If the request fails the timer stays armed.

A second call to corkscrew_open will unconditionally reinitialize the
quued timer and arm it again. Also a immediate device removal will leave
the timer queued because close() is not called (open() failed) and
therefore nothing issues del_timer().

The reinitialization corrupts the link chain in the timer wheel hash
bucket and causes a NULL pointer dereference when the timer wheel tries
to operate on that hash bucket. Immediate device removal lets the link
chain poke into freed and possibly reused memory.

Solution: Arm the timer after the successful irq request.

- corkscrew_close() uses del_timer()

On close the timer is disarmed with del_timer() which lets the following
code race against a concurrent timer expiry function.

Solution: Use del_timer_sync() instead

- corkscrew_close() calls del_timer() unconditionally

del_timer() is invoked even if the timer was never initialized. This
works by chance because the struct containing the timer is zeroed at
allocation time.

Solution: Move the setup of the timer into corkscrew_setup().

Reported-by: Matthew Whitehead <tedheadster@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: netdev@vger.kernel.org
---
drivers/net/ethernet/3com/3c515.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

--- a/drivers/net/ethernet/3com/3c515.c
+++ b/drivers/net/ethernet/3com/3c515.c
@@ -628,6 +628,8 @@ static int corkscrew_setup(struct net_de

spin_lock_init(&vp->lock);

+ setup_timer(&vp->timer, corkscrew_timer, (unsigned long) dev);
+
/* Read the station address from the EEPROM. */
EL3WINDOW(0);
for (i = 0; i < 0x18; i++) {
@@ -708,6 +710,7 @@ static int corkscrew_open(struct net_dev
{
int ioaddr = dev->base_addr;
struct corkscrew_private *vp = netdev_priv(dev);
+ bool armtimer = false;
__u32 config;
int i;

@@ -732,12 +735,7 @@ static int corkscrew_open(struct net_dev
if (corkscrew_debug > 1)
pr_debug("%s: Initial media type %s.\n",
dev->name, media_tbl[dev->if_port].name);
-
- init_timer(&vp->timer);
- vp->timer.expires = jiffies + media_tbl[dev->if_port].wait;
- vp->timer.data = (unsigned long) dev;
- vp->timer.function = corkscrew_timer; /* timer handler */
- add_timer(&vp->timer);
+ armtimer = true;
} else
dev->if_port = vp->default_media;

@@ -777,6 +775,9 @@ static int corkscrew_open(struct net_dev
return -EAGAIN;
}

+ if (armtimer)
+ mod_timer(&vp->timer, jiffies + media_tbl[dev->if_port].wait);
+
if (corkscrew_debug > 1) {
EL3WINDOW(4);
pr_debug("%s: corkscrew_open() irq %d media status %4.4x.\n",
@@ -1427,7 +1428,7 @@ static int corkscrew_close(struct net_de
dev->name, rx_nocopy, rx_copy, queued_packet);
}

- del_timer(&vp->timer);
+ del_timer_sync(&vp->timer);

/* Turn off statistics ASAP. We update lp->stats below. */
outw(StatsDisable, ioaddr + EL3_CMD);
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