From 2459dcb96bcba94c08d6861f8a050185ff301672 Mon Sep 17 00:00:00 2001 From: Pali Rohár Date: Sat, 7 Aug 2021 15:27:03 +0200 Subject: ppp: Fix generating ifname when empty IFLA_IFNAME is specified MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit IFLA_IFNAME is nul-term string which means that IFLA_IFNAME buffer can be larger than length of string which contains. Function __rtnl_newlink() generates new own ifname if either IFLA_IFNAME was not specified at all or userspace passed empty nul-term string. It is expected that if userspace does not specify ifname for new ppp netdev then kernel generates one in format "ppp" where id matches to the ppp unit id which can be later obtained by PPPIOCGUNIT ioctl. And it works in this way if IFLA_IFNAME is not specified at all. But it does not work when IFLA_IFNAME is specified with empty string. So fix this logic also for empty IFLA_IFNAME in ppp_nl_newlink() function and correctly generates ifname based on ppp unit identifier if userspace did not provided preferred ifname. Without this patch when IFLA_IFNAME was specified with empty string then kernel created a new ppp interface in format "ppp" but id did not match ppp unit id returned by PPPIOCGUNIT ioctl. In this case id was some number generated by __rtnl_newlink() function. Signed-off-by: Pali Rohár Fixes: bb8082f69138 ("ppp: build ifname using unit identifier for rtnl based devices") Signed-off-by: David S. Miller --- drivers/net/ppp/ppp_generic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/net/ppp') diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 930e49ef15f6..b2b35ec37702 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -1306,7 +1306,7 @@ static int ppp_nl_newlink(struct net *src_net, struct net_device *dev, * the PPP unit identifer as suffix (i.e. ppp). This allows * userspace to infer the device name using to the PPPIOCGUNIT ioctl. */ - if (!tb[IFLA_IFNAME]) + if (!tb[IFLA_IFNAME] || !nla_len(tb[IFLA_IFNAME]) || !*(char *)nla_data(tb[IFLA_IFNAME])) conf.ifname_is_set = false; err = ppp_dev_configure(src_net, dev, &conf); -- cgit v1.2.3 From 3125f26c514826077f2a4490b75e9b1c7a644c42 Mon Sep 17 00:00:00 2001 From: Pali Rohár Date: Sat, 7 Aug 2021 18:00:50 +0200 Subject: ppp: Fix generating ppp unit id when ifname is not specified MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When registering new ppp interface via PPPIOCNEWUNIT ioctl then kernel has to choose interface name as this ioctl API does not support specifying it. Kernel in this case register new interface with name "ppp" where is the ppp unit id, which can be obtained via PPPIOCGUNIT ioctl. This applies also in the case when registering new ppp interface via rtnl without supplying IFLA_IFNAME. PPPIOCNEWUNIT ioctl allows to specify own ppp unit id which will kernel assign to ppp interface, in case this ppp id is not already used by other ppp interface. In case user does not specify ppp unit id then kernel choose the first free ppp unit id. This applies also for case when creating ppp interface via rtnl method as it does not provide a way for specifying own ppp unit id. If some network interface (does not have to be ppp) has name "ppp" with this first free ppp id then PPPIOCNEWUNIT ioctl or rtnl call fails. And registering new ppp interface is not possible anymore, until interface which holds conflicting name is renamed. Or when using rtnl method with custom interface name in IFLA_IFNAME. As list of allocated / used ppp unit ids is not possible to retrieve from kernel to userspace, userspace has no idea what happens nor which interface is doing this conflict. So change the algorithm how ppp unit id is generated. And choose the first number which is not neither used as ppp unit id nor in some network interface with pattern "ppp". This issue can be simply reproduced by following pppd call when there is no ppp interface registered and also no interface with name pattern "ppp": pppd ifname ppp1 +ipv6 noip noauth nolock local nodetach pty "pppd +ipv6 noip noauth nolock local nodetach notty" Or by creating the one ppp interface (which gets assigned ppp unit id 0), renaming it to "ppp1" and then trying to create a new ppp interface (which will always fails as next free ppp unit id is 1, but network interface with name "ppp1" exists). This patch fixes above described issue by generating new and new ppp unit id until some non-conflicting id with network interfaces is generated. Signed-off-by: Pali Rohár Cc: stable@vger.kernel.org Signed-off-by: David S. Miller --- drivers/net/ppp/ppp_generic.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) (limited to 'drivers/net/ppp') diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index b2b35ec37702..7a099c37527f 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -284,7 +284,7 @@ static struct channel *ppp_find_channel(struct ppp_net *pn, int unit); static int ppp_connect_channel(struct channel *pch, int unit); static int ppp_disconnect_channel(struct channel *pch); static void ppp_destroy_channel(struct channel *pch); -static int unit_get(struct idr *p, void *ptr); +static int unit_get(struct idr *p, void *ptr, int min); static int unit_set(struct idr *p, void *ptr, int n); static void unit_put(struct idr *p, int n); static void *unit_find(struct idr *p, int n); @@ -1155,9 +1155,20 @@ static int ppp_unit_register(struct ppp *ppp, int unit, bool ifname_is_set) mutex_lock(&pn->all_ppp_mutex); if (unit < 0) { - ret = unit_get(&pn->units_idr, ppp); + ret = unit_get(&pn->units_idr, ppp, 0); if (ret < 0) goto err; + if (!ifname_is_set) { + while (1) { + snprintf(ppp->dev->name, IFNAMSIZ, "ppp%i", ret); + if (!__dev_get_by_name(ppp->ppp_net, ppp->dev->name)) + break; + unit_put(&pn->units_idr, ret); + ret = unit_get(&pn->units_idr, ppp, ret + 1); + if (ret < 0) + goto err; + } + } } else { /* Caller asked for a specific unit number. Fail with -EEXIST * if unavailable. For backward compatibility, return -EEXIST @@ -3552,9 +3563,9 @@ static int unit_set(struct idr *p, void *ptr, int n) } /* get new free unit number and associate pointer with it */ -static int unit_get(struct idr *p, void *ptr) +static int unit_get(struct idr *p, void *ptr, int min) { - return idr_alloc(p, ptr, 0, 0, GFP_KERNEL); + return idr_alloc(p, ptr, min, 0, GFP_KERNEL); } /* put unit number back to a pool */ -- cgit v1.2.3