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rtnetlink: use dev_isalive() in rtnl_getlink()

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rtnl_getlink() uses an RCU lookup to get the netdevice pointer.

When/If rtnl_lock() is used, we should check if the netdevice is not
being dismantled before potentially perform illegal actions.

Move dev_isalive() out of net/core/net-sysfs.c and make it available
in net/core/dev.h.

Return -ENODEV if rtnl_getlink() finds a device which is currently
being dismantled and RTNL is requested.

Fixes: e896e5c073 ("rtnetlink: do not acquire RTNL in rtnl_getlink() with RTEXT_FILTER_NAME_ONLY")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://patch.msgid.link/20260603180831.1024716-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-06-03 18:08:31 +00:00 committed by Jakub Kicinski
parent c1424df7ff
commit f3c4961054
3 changed files with 12 additions and 6 deletions
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6
net/core/dev.h
View File

@ -396,4 +396,10 @@ int dev_get_hwtstamp_phylib(struct net_device *dev,
struct kernel_hwtstamp_config *cfg);
int net_hwtstamp_validate(const struct kernel_hwtstamp_config *cfg);
/* Caller holds RTNL, netdev->lock or RCU */
static inline bool dev_isalive(const struct net_device *dev)
{
return READ_ONCE(dev->reg_state) <= NETREG_REGISTERED;
}
#endif

6
net/core/net-sysfs.c
View File

@ -37,12 +37,6 @@ static const char fmt_uint[] = "%u\n";
static const char fmt_ulong[] = "%lu\n";
static const char fmt_u64[] = "%llu\n";
/* Caller holds RTNL, netdev->lock or RCU */
static inline int dev_isalive(const struct net_device *dev)
{
return READ_ONCE(dev->reg_state) <= NETREG_REGISTERED;
}
/* There is a possible ABBA deadlock between rtnl_lock and kernfs_node->active,
* when unregistering a net device and accessing associated sysfs files. The
* potential deadlock is as follow:

6
net/core/rtnetlink.c
View File

@ -4265,6 +4265,11 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
retry:
if (need_rtnl) {
rtnl_lock();
if (!dev_isalive(dev)) {
err = -ENODEV;
nskb = NULL;
goto unlock;
}
/* Synchronize the carrier state so we don't report a state
* that we're not actually going to honour immediately; if
* the driver just did a carrier off->on transition, we can
@ -4282,6 +4287,7 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
nlh->nlmsg_seq, 0, 0, ext_filter_mask,
0, NULL, 0, netnsid, GFP_KERNEL);
unlock:
if (need_rtnl)
rtnl_unlock();