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ipv6/addrconf: fix a potential refcount underflow for idev

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Now in addrconf_mod_rs_timer(), reference idev depends on whether
rs_timer is not pending. Then modify rs_timer timeout.

There is a time gap in [1], during which if the pending rs_timer
becomes not pending. It will miss to hold idev, but the rs_timer
is activated. Thus rs_timer callback function addrconf_rs_timer()
will be executed and put idev later without holding idev. A refcount
underflow issue for idev can be caused by this.

	if (!timer_pending(&idev->rs_timer))
		in6_dev_hold(idev);
		  <--------------[1]
	mod_timer(&idev->rs_timer, jiffies + when);

To fix the issue, hold idev if mod_timer() return 0.

Fixes: b7b1bfce0b ("ipv6: split duplicate address detection and router solicitation timer")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ziyang Xuan 2023-07-08 14:59:10 +08:00 committed by David S. Miller
parent 51d03e2f22
commit 06a0716949
1 changed files with 1 additions and 2 deletions
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3
net/ipv6/addrconf.c
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@ -318,9 +318,8 @@ static void addrconf_del_dad_work(struct inet6_ifaddr *ifp)
static void addrconf_mod_rs_timer(struct inet6_dev *idev, static void addrconf_mod_rs_timer(struct inet6_dev *idev,
unsigned long when) unsigned long when)
{ {
if (!timer_pending(&idev->rs_timer)) if (!mod_timer(&idev->rs_timer, jiffies + when))
in6_dev_hold(idev); in6_dev_hold(idev);
mod_timer(&idev->rs_timer, jiffies + when);
} }
static void addrconf_mod_dad_work(struct inet6_ifaddr *ifp, static void addrconf_mod_dad_work(struct inet6_ifaddr *ifp,