6.6-stable review patch. If anyone has any objections, please let me know.
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From: Phil Sutter phil@nwl.cc
[ Upstream commit f36b01994d68ffc253c8296e2228dfe6e6431c03 ]
Deletion of the last rule referencing a given idletimer may happen at the same time as a read of its file in sysfs:
| ====================================================== | WARNING: possible circular locking dependency detected | 6.12.0-rc7-01692-g5e9a28f41134-dirty #594 Not tainted | ------------------------------------------------------ | iptables/3303 is trying to acquire lock: | ffff8881057e04b8 (kn->active#48){++++}-{0:0}, at: __kernfs_remove+0x20 | | but task is already holding lock: | ffffffffa0249068 (list_mutex){+.+.}-{3:3}, at: idletimer_tg_destroy_v] | | which lock already depends on the new lock.
A simple reproducer is:
| #!/bin/bash | | while true; do | iptables -A INPUT -i foo -j IDLETIMER --timeout 10 --label "testme" | iptables -D INPUT -i foo -j IDLETIMER --timeout 10 --label "testme" | done & | while true; do | cat /sys/class/xt_idletimer/timers/testme >/dev/null | done
Avoid this by freeing list_mutex right after deleting the element from the list, then continuing with the teardown.
Fixes: 0902b469bd25 ("netfilter: xtables: idletimer target implementation") Signed-off-by: Phil Sutter phil@nwl.cc Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/netfilter/xt_IDLETIMER.c | 52 +++++++++++++++++++----------------- 1 file changed, 28 insertions(+), 24 deletions(-)
diff --git a/net/netfilter/xt_IDLETIMER.c b/net/netfilter/xt_IDLETIMER.c index f8b25b6f5da7..9869ef3c2ab3 100644 --- a/net/netfilter/xt_IDLETIMER.c +++ b/net/netfilter/xt_IDLETIMER.c @@ -409,21 +409,23 @@ static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
mutex_lock(&list_mutex);
- if (--info->timer->refcnt == 0) { - pr_debug("deleting timer %s\n", info->label); - - list_del(&info->timer->entry); - timer_shutdown_sync(&info->timer->timer); - cancel_work_sync(&info->timer->work); - sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); - kfree(info->timer->attr.attr.name); - kfree(info->timer); - } else { + if (--info->timer->refcnt > 0) { pr_debug("decreased refcnt of timer %s to %u\n", info->label, info->timer->refcnt); + mutex_unlock(&list_mutex); + return; }
+ pr_debug("deleting timer %s\n", info->label); + + list_del(&info->timer->entry); mutex_unlock(&list_mutex); + + timer_shutdown_sync(&info->timer->timer); + cancel_work_sync(&info->timer->work); + sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); + kfree(info->timer->attr.attr.name); + kfree(info->timer); }
static void idletimer_tg_destroy_v1(const struct xt_tgdtor_param *par) @@ -434,25 +436,27 @@ static void idletimer_tg_destroy_v1(const struct xt_tgdtor_param *par)
mutex_lock(&list_mutex);
- if (--info->timer->refcnt == 0) { - pr_debug("deleting timer %s\n", info->label); - - list_del(&info->timer->entry); - if (info->timer->timer_type & XT_IDLETIMER_ALARM) { - alarm_cancel(&info->timer->alarm); - } else { - timer_shutdown_sync(&info->timer->timer); - } - cancel_work_sync(&info->timer->work); - sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); - kfree(info->timer->attr.attr.name); - kfree(info->timer); - } else { + if (--info->timer->refcnt > 0) { pr_debug("decreased refcnt of timer %s to %u\n", info->label, info->timer->refcnt); + mutex_unlock(&list_mutex); + return; }
+ pr_debug("deleting timer %s\n", info->label); + + list_del(&info->timer->entry); mutex_unlock(&list_mutex); + + if (info->timer->timer_type & XT_IDLETIMER_ALARM) { + alarm_cancel(&info->timer->alarm); + } else { + timer_shutdown_sync(&info->timer->timer); + } + cancel_work_sync(&info->timer->work); + sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); + kfree(info->timer->attr.attr.name); + kfree(info->timer); }