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author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-20 10:23:48 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-10-22 04:22:39 +0300 |
commit | 709c89b45b874b2f81a074b8802a736009873f48 (patch) | |
tree | 80ef98e8c9744487746d29eb1313d39762a08ac8 /drivers/net/ppp/ppp_synctty.c | |
parent | d780cd44e3cea119a3346e6d7c04d35b9c50d54b (diff) | |
download | linux-709c89b45b874b2f81a074b8802a736009873f48.tar.xz |
drivers, net, ppp: convert syncppp.refcnt from atomic_t to refcount_t
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable syncppp.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ppp/ppp_synctty.c')
-rw-r--r-- | drivers/net/ppp/ppp_synctty.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c index 7868c29071d4..7196f00f0991 100644 --- a/drivers/net/ppp/ppp_synctty.c +++ b/drivers/net/ppp/ppp_synctty.c @@ -46,6 +46,7 @@ #include <linux/init.h> #include <linux/interrupt.h> #include <linux/slab.h> +#include <linux/refcount.h> #include <asm/unaligned.h> #include <linux/uaccess.h> @@ -72,7 +73,7 @@ struct syncppp { struct tasklet_struct tsk; - atomic_t refcnt; + refcount_t refcnt; struct completion dead_cmp; struct ppp_channel chan; /* interface to generic ppp layer */ }; @@ -141,14 +142,14 @@ static struct syncppp *sp_get(struct tty_struct *tty) read_lock(&disc_data_lock); ap = tty->disc_data; if (ap != NULL) - atomic_inc(&ap->refcnt); + refcount_inc(&ap->refcnt); read_unlock(&disc_data_lock); return ap; } static void sp_put(struct syncppp *ap) { - if (atomic_dec_and_test(&ap->refcnt)) + if (refcount_dec_and_test(&ap->refcnt)) complete(&ap->dead_cmp); } @@ -182,7 +183,7 @@ ppp_sync_open(struct tty_struct *tty) skb_queue_head_init(&ap->rqueue); tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap); - atomic_set(&ap->refcnt, 1); + refcount_set(&ap->refcnt, 1); init_completion(&ap->dead_cmp); ap->chan.private = ap; @@ -232,7 +233,7 @@ ppp_sync_close(struct tty_struct *tty) * our channel ops (i.e. ppp_sync_send/ioctl) are in progress * by the time it returns. */ - if (!atomic_dec_and_test(&ap->refcnt)) + if (!refcount_dec_and_test(&ap->refcnt)) wait_for_completion(&ap->dead_cmp); tasklet_kill(&ap->tsk); |