| Message ID | 8a9519431c30c6baa9c2135552009fcab850ae08.1646981034.git.duoming@zju.edu.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Fix refcount leak and NPD bugs in ax25 | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Clearly marked for net |
| netdev/fixes_present | success | Fixes tag present in non-next series |
| netdev/subject_prefix | success | Link |
| netdev/cover_letter | success | Series has a cover letter |
| netdev/patch_count | success | Link |
| netdev/header_inline | success | No static functions without inline keyword in header files |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/cc_maintainers | success | CCed 6 of 6 maintainers |
| netdev/build_clang | success | Errors and warnings before: 0 this patch: 0 |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Signed-off-by tag matches author and committer |
| netdev/verify_fixes | success | No Fixes tag |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 61 lines checked |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/source_inline | success | Was 0 now: 0 |
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index fc564b87acc..46e4d0cc878 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -90,18 +90,18 @@ static void ax25_kill_by_device(struct net_device *dev) sk = s->sk; if (!sk) { spin_unlock_bh(&ax25_list_lock); - s->ax25_dev = NULL; ax25_disconnect(s, ENETUNREACH); + s->ax25_dev = NULL; spin_lock_bh(&ax25_list_lock); goto again; } sock_hold(sk); spin_unlock_bh(&ax25_list_lock); lock_sock(sk); + ax25_disconnect(s, ENETUNREACH); s->ax25_dev = NULL; dev_put_track(ax25_dev->dev, &ax25_dev->dev_tracker); ax25_dev_put(ax25_dev); - ax25_disconnect(s, ENETUNREACH); release_sock(sk); spin_lock_bh(&ax25_list_lock); sock_put(sk); @@ -310,7 +310,8 @@ void ax25_destroy_socket(ax25_cb *ax25) ax25_cb_del(ax25); - ax25_stop_heartbeat(ax25); + if (!ax25->sk || !sock_flag(ax25->sk, SOCK_DESTROY)) + ax25_stop_heartbeat(ax25); ax25_stop_t1timer(ax25); ax25_stop_t2timer(ax25); ax25_stop_t3timer(ax25); diff --git a/net/ax25/ax25_timer.c b/net/ax25/ax25_timer.c index 85865ebfdfa..99af3d1aeec 100644 --- a/net/ax25/ax25_timer.c +++ b/net/ax25/ax25_timer.c @@ -78,27 +78,27 @@ void ax25_start_idletimer(ax25_cb *ax25) void ax25_stop_heartbeat(ax25_cb *ax25) { - del_timer(&ax25->timer); + del_timer_sync(&ax25->timer); } void ax25_stop_t1timer(ax25_cb *ax25) { - del_timer(&ax25->t1timer); + del_timer_sync(&ax25->t1timer); } void ax25_stop_t2timer(ax25_cb *ax25) { - del_timer(&ax25->t2timer); + del_timer_sync(&ax25->t2timer); } void ax25_stop_t3timer(ax25_cb *ax25) { - del_timer(&ax25->t3timer); + del_timer_sync(&ax25->t3timer); } void ax25_stop_idletimer(ax25_cb *ax25) { - del_timer(&ax25->idletimer); + del_timer_sync(&ax25->idletimer); } int ax25_t1timer_running(ax25_cb *ax25)
There are race conditions that may lead to null pointer dereferences in ax25_heartbeat_expiry(), ax25_t1timer_expiry(), ax25_t2timer_expiry(), ax25_t3timer_expiry() and ax25_idletimer_expiry(), when we use ax25_kill_by_device() to detach the ax25 device. One of the race conditions that cause null pointer dereferences can be shown as below: (Thread 1) | (Thread 2) ax25_connect() | ax25_std_establish_data_link() | ax25_start_t1timer() | mod_timer(&ax25->t1timer,..) | | ax25_kill_by_device() (wait a time) | ... | s->ax25_dev = NULL; //(1) ax25_t1timer_expiry() | ax25->ax25_dev->values[..] //(2)| ... ... | We set null to ax25_cb->ax25_dev in position (1) and dereference the null pointer in position (2). The corresponding fail log is shown below: =============================================================== BUG: kernel NULL pointer dereference, address: 0000000000000050 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc6-00794-g45690b7d0 RIP: 0010:ax25_t1timer_expiry+0x12/0x40 ... Call Trace: call_timer_fn+0x21/0x120 __run_timers.part.0+0x1ca/0x250 run_timer_softirq+0x2c/0x60 __do_softirq+0xef/0x2f3 irq_exit_rcu+0xb6/0x100 sysvec_apic_timer_interrupt+0xa2/0xd0 ... This patch uses ax25_disconnect() to delete timers before we set null to ax25_cb->ax25_dev in ax25_kill_by_device(). Function ax25_disconnect() will not return until all timers are stopped, because we have changed del_timer() to del_timer_sync(). What`s more, we add condition check in ax25_destroy_socket(), because ax25_stop_heartbeat() will not return, if there is still heartbeat. Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- net/ax25/af_ax25.c | 7 ++++--- net/ax25/ax25_timer.c | 10 +++++----- 2 files changed, 9 insertions(+), 8 deletions(-)