Hi Alan,
Sorry correcting the typo here:
+retval = tty_ldisc_lock(tty, 5 * HZ);
+if (retval)
+ goto err_release_lock;
tty->port->itty = tty;
/*
* Structures all installed ... call the ldisc open routines.
* If we fail here just call release_tty to clean up. No need
* to decrement the use counts, as release_tty doesn't care.
*/
retval = tty_ldisc_setup(tty, tty->link);
if (retval)
goto err_release_tty;
tty_ldisc_unlock(tty);
err_release_tty:
tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
retval, idx);
+err_release_lock;
+tty_unlock(tty);
+release_tty(tty, idx);
+tty_ldisc_unlock(tty);
+return ERR_PTR(retval);
On 1/6/2018 1:44 AM, Kohli, Gaurav wrote:
Hi Alan,
On 1/5/2018 7:45 PM, Alan Cox wrote:
But in above case , there we can hit another race, if we have a
sequence
like this
tty_init_dev->alloc_tty_struct -> tty_ldisc_init -> this will
initialize
ldisc ,
but at this moment disc_data is still NULL
And if flush_to_ldisc comes in between, it will take ldisc reference
and
proceeds receive buffer.
So you need to move the lock up one line to protect the assignment to
tty->port->itty. We can do that.
At that point your flush_to_ldisc should see either port->itty = NULL
or a
valid initialized ldisc.
Yes , with little modification this should work.
+retval = tty_ldisc_lock(tty, 5 * HZ);
+if (retval)
+ goto err_release_lock;
tty->port->itty = tty;
/*
* Structures all installed ... call the ldisc open routines.
* If we fail here just call release_tty to clean up. No need
* to decrement the use counts, as release_tty doesn't care.
*/
retval = tty_ldisc_setup(tty, tty->link);
if (retval)
goto err_release_tty;
tty_ldisc_unlock(tty);
err_release_tty:
tty_unlock(tty);
tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
retval, idx);
release_tty(tty, idx);
return ERR_PTR(retval);
+err_release_lock;
+tty_ldisc_unlock(tty);
+return ERR_PTR(retval);
Please let me know if above modification seems fine , then we can
upload this and try reproduction of Bug.
Regards
Gaurav
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