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ppp: require callers of ppp_dev_name() to hold RCU

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ppp_dev_name() holds the RCU read lock internally to protect pch->ppp.
However, as it returns netdev->name to the caller, the caller should
also hold either RCU or RTNL lock to prevent the netdev from being
freed.

The only two references of the function is in the L2TP driver, both of
which already hold RCU. So remove the internal RCU lock and document
that callers must hold RCU.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260316092824.479149-1-dqfext@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Qingfang Deng
2026-03-16 17:28:23 +08:00
committed by Jakub Kicinski
parent e3f741f587
commit bb8539e0e6
2 changed files with 4 additions and 3 deletions
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3
drivers/net/ppp/ppp_generic.c
View File

@@ -2969,6 +2969,7 @@ int ppp_unit_number(struct ppp_channel *chan)
/*
* Return the PPP device interface name of a channel.
* Caller must hold RCU read lock.
*/
char *ppp_dev_name(struct ppp_channel *chan)
{
@@ -2977,11 +2978,9 @@ char *ppp_dev_name(struct ppp_channel *chan)
struct ppp *ppp;
if (pch) {
rcu_read_lock();
ppp = rcu_dereference(pch->ppp);
if (ppp && ppp->dev)
name = ppp->dev->name;
rcu_read_unlock();
}
return name;
}

4
include/linux/ppp_channel.h
View File

@@ -72,7 +72,9 @@ extern int ppp_channel_index(struct ppp_channel *);
/* Get the unit number associated with a channel, or -1 if none */
extern int ppp_unit_number(struct ppp_channel *);
/* Get the device name associated with a channel, or NULL if none */
/* Get the device name associated with a channel, or NULL if none.
* Caller must hold RCU read lock.
*/
extern char *ppp_dev_name(struct ppp_channel *);
/*