From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: linux-can@vger.kernel.org, tglx@linutronix.de,
Marc Kleine-Budde <mkl@pengutronix.de>
Subject: [PATCH v2] can: gw: fix RCU/BH usage in cgw_create_job()
Date: Tue, 29 Apr 2025 09:05:55 +0200 [thread overview]
Message-ID: <20250429070555.cs-7b_eZ@linutronix.de> (raw)
From: Oliver Hartkopp <socketcan@hartkopp.net>
As reported by Sebastian Andrzej Siewior the use of local_bh_disable()
is only feasible in uni processor systems to update the modification rules.
The usual use-case to update the modification rules is to update the data
of the modifications but not the modification types (AND/OR/XOR/SET) or
the checksum functions itself.
To omit additional memory allocations to maintain fast modification
switching times, the modification description space is doubled at gw-job
creation time so that only the reference to the active modification
desciption is changed under rcu protection.
Rename cgw_job::mod to cf_mod and make it a RCU pointer. Allocate in
cgw_create_job() and free it together with cgw_job in
cgw_job_free_rcu(). Update all users to dereference cgw_job::cf_mod with
a RCU accessor and if possible once.
[bigeasy: Replace mod1/mod2 from the Oliver's original patch with dynamic
allocation, use RCU annotation and accessor]
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Closes: https://lore.kernel.org/linux-can/20231031112349.y0aLoBrz@linutronix.de/
Fixes: dd895d7f21b2 ("can: cangw: introduce optional uid to reference created routing jobs")
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
v1…v2: https://lore.kernel.org/all/20250417144122.LVyWdXXO@linutronix.de/
- Add brackets around the error free in cgw_create_job() so that the
NULL assignment to mod can be avoided.
- Add Oliver's tested-by.
net/can/gw.c | 151 +++++++++++++++++++++++++++++++--------------------
1 file changed, 91 insertions(+), 60 deletions(-)
diff --git a/net/can/gw.c b/net/can/gw.c
index ef93293c1fae3..55eccb1c7620c 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -130,7 +130,7 @@ struct cgw_job {
u32 handled_frames;
u32 dropped_frames;
u32 deleted_frames;
- struct cf_mod mod;
+ struct cf_mod __rcu *cf_mod;
union {
/* CAN frame data source */
struct net_device *dev;
@@ -459,6 +459,7 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
struct cgw_job *gwj = (struct cgw_job *)data;
struct canfd_frame *cf;
struct sk_buff *nskb;
+ struct cf_mod *mod;
int modidx = 0;
/* process strictly Classic CAN or CAN FD frames */
@@ -506,7 +507,8 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
* When there is at least one modification function activated,
* we need to copy the skb as we want to modify skb->data.
*/
- if (gwj->mod.modfunc[0])
+ mod = rcu_dereference(gwj->cf_mod);
+ if (mod->modfunc[0])
nskb = skb_copy(skb, GFP_ATOMIC);
else
nskb = skb_clone(skb, GFP_ATOMIC);
@@ -529,8 +531,8 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
cf = (struct canfd_frame *)nskb->data;
/* perform preprocessed modification functions if there are any */
- while (modidx < MAX_MODFUNCTIONS && gwj->mod.modfunc[modidx])
- (*gwj->mod.modfunc[modidx++])(cf, &gwj->mod);
+ while (modidx < MAX_MODFUNCTIONS && mod->modfunc[modidx])
+ (*mod->modfunc[modidx++])(cf, mod);
/* Has the CAN frame been modified? */
if (modidx) {
@@ -546,11 +548,11 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
}
/* check for checksum updates */
- if (gwj->mod.csumfunc.crc8)
- (*gwj->mod.csumfunc.crc8)(cf, &gwj->mod.csum.crc8);
+ if (mod->csumfunc.crc8)
+ (*mod->csumfunc.crc8)(cf, &mod->csum.crc8);
- if (gwj->mod.csumfunc.xor)
- (*gwj->mod.csumfunc.xor)(cf, &gwj->mod.csum.xor);
+ if (mod->csumfunc.xor)
+ (*mod->csumfunc.xor)(cf, &mod->csum.xor);
}
/* clear the skb timestamp if not configured the other way */
@@ -581,9 +583,20 @@ static void cgw_job_free_rcu(struct rcu_head *rcu_head)
{
struct cgw_job *gwj = container_of(rcu_head, struct cgw_job, rcu);
+ /* cgw_job::cf_mod is always accessed from the same cgw_job object within
+ * the same RCU read section. Once cgw_job is scheduled for removal,
+ * cf_mod can also be removed without mandating an additional grace period.
+ */
+ kfree(rcu_access_pointer(gwj->cf_mod));
kmem_cache_free(cgw_cache, gwj);
}
+/* Return cgw_job::cf_mod with RTNL protected section */
+static struct cf_mod *cgw_job_cf_mod(struct cgw_job *gwj)
+{
+ return rcu_dereference_protected(gwj->cf_mod, rtnl_is_locked());
+}
+
static int cgw_notifier(struct notifier_block *nb,
unsigned long msg, void *ptr)
{
@@ -616,6 +629,7 @@ static int cgw_put_job(struct sk_buff *skb, struct cgw_job *gwj, int type,
{
struct rtcanmsg *rtcan;
struct nlmsghdr *nlh;
+ struct cf_mod *mod;
nlh = nlmsg_put(skb, pid, seq, type, sizeof(*rtcan), flags);
if (!nlh)
@@ -650,82 +664,83 @@ static int cgw_put_job(struct sk_buff *skb, struct cgw_job *gwj, int type,
goto cancel;
}
+ mod = cgw_job_cf_mod(gwj);
if (gwj->flags & CGW_FLAGS_CAN_FD) {
struct cgw_fdframe_mod mb;
- if (gwj->mod.modtype.and) {
- memcpy(&mb.cf, &gwj->mod.modframe.and, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.and;
+ if (mod->modtype.and) {
+ memcpy(&mb.cf, &mod->modframe.and, sizeof(mb.cf));
+ mb.modtype = mod->modtype.and;
if (nla_put(skb, CGW_FDMOD_AND, sizeof(mb), &mb) < 0)
goto cancel;
}
- if (gwj->mod.modtype.or) {
- memcpy(&mb.cf, &gwj->mod.modframe.or, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.or;
+ if (mod->modtype.or) {
+ memcpy(&mb.cf, &mod->modframe.or, sizeof(mb.cf));
+ mb.modtype = mod->modtype.or;
if (nla_put(skb, CGW_FDMOD_OR, sizeof(mb), &mb) < 0)
goto cancel;
}
- if (gwj->mod.modtype.xor) {
- memcpy(&mb.cf, &gwj->mod.modframe.xor, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.xor;
+ if (mod->modtype.xor) {
+ memcpy(&mb.cf, &mod->modframe.xor, sizeof(mb.cf));
+ mb.modtype = mod->modtype.xor;
if (nla_put(skb, CGW_FDMOD_XOR, sizeof(mb), &mb) < 0)
goto cancel;
}
- if (gwj->mod.modtype.set) {
- memcpy(&mb.cf, &gwj->mod.modframe.set, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.set;
+ if (mod->modtype.set) {
+ memcpy(&mb.cf, &mod->modframe.set, sizeof(mb.cf));
+ mb.modtype = mod->modtype.set;
if (nla_put(skb, CGW_FDMOD_SET, sizeof(mb), &mb) < 0)
goto cancel;
}
} else {
struct cgw_frame_mod mb;
- if (gwj->mod.modtype.and) {
- memcpy(&mb.cf, &gwj->mod.modframe.and, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.and;
+ if (mod->modtype.and) {
+ memcpy(&mb.cf, &mod->modframe.and, sizeof(mb.cf));
+ mb.modtype = mod->modtype.and;
if (nla_put(skb, CGW_MOD_AND, sizeof(mb), &mb) < 0)
goto cancel;
}
- if (gwj->mod.modtype.or) {
- memcpy(&mb.cf, &gwj->mod.modframe.or, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.or;
+ if (mod->modtype.or) {
+ memcpy(&mb.cf, &mod->modframe.or, sizeof(mb.cf));
+ mb.modtype = mod->modtype.or;
if (nla_put(skb, CGW_MOD_OR, sizeof(mb), &mb) < 0)
goto cancel;
}
- if (gwj->mod.modtype.xor) {
- memcpy(&mb.cf, &gwj->mod.modframe.xor, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.xor;
+ if (mod->modtype.xor) {
+ memcpy(&mb.cf, &mod->modframe.xor, sizeof(mb.cf));
+ mb.modtype = mod->modtype.xor;
if (nla_put(skb, CGW_MOD_XOR, sizeof(mb), &mb) < 0)
goto cancel;
}
- if (gwj->mod.modtype.set) {
- memcpy(&mb.cf, &gwj->mod.modframe.set, sizeof(mb.cf));
- mb.modtype = gwj->mod.modtype.set;
+ if (mod->modtype.set) {
+ memcpy(&mb.cf, &mod->modframe.set, sizeof(mb.cf));
+ mb.modtype = mod->modtype.set;
if (nla_put(skb, CGW_MOD_SET, sizeof(mb), &mb) < 0)
goto cancel;
}
}
- if (gwj->mod.uid) {
- if (nla_put_u32(skb, CGW_MOD_UID, gwj->mod.uid) < 0)
+ if (mod->uid) {
+ if (nla_put_u32(skb, CGW_MOD_UID, mod->uid) < 0)
goto cancel;
}
- if (gwj->mod.csumfunc.crc8) {
+ if (mod->csumfunc.crc8) {
if (nla_put(skb, CGW_CS_CRC8, CGW_CS_CRC8_LEN,
- &gwj->mod.csum.crc8) < 0)
+ &mod->csum.crc8) < 0)
goto cancel;
}
- if (gwj->mod.csumfunc.xor) {
+ if (mod->csumfunc.xor) {
if (nla_put(skb, CGW_CS_XOR, CGW_CS_XOR_LEN,
- &gwj->mod.csum.xor) < 0)
+ &mod->csum.xor) < 0)
goto cancel;
}
@@ -1059,7 +1074,7 @@ static int cgw_create_job(struct sk_buff *skb, struct nlmsghdr *nlh,
struct net *net = sock_net(skb->sk);
struct rtcanmsg *r;
struct cgw_job *gwj;
- struct cf_mod mod;
+ struct cf_mod *mod;
struct can_can_gw ccgw;
u8 limhops = 0;
int err = 0;
@@ -1078,37 +1093,48 @@ static int cgw_create_job(struct sk_buff *skb, struct nlmsghdr *nlh,
if (r->gwtype != CGW_TYPE_CAN_CAN)
return -EINVAL;
- err = cgw_parse_attr(nlh, &mod, CGW_TYPE_CAN_CAN, &ccgw, &limhops);
- if (err < 0)
- return err;
+ mod = kmalloc(sizeof(*mod), GFP_KERNEL);
+ if (!mod)
+ return -ENOMEM;
- if (mod.uid) {
+ err = cgw_parse_attr(nlh, mod, CGW_TYPE_CAN_CAN, &ccgw, &limhops);
+ if (err < 0)
+ goto out_free_cf;
+
+ if (mod->uid) {
ASSERT_RTNL();
/* check for updating an existing job with identical uid */
hlist_for_each_entry(gwj, &net->can.cgw_list, list) {
- if (gwj->mod.uid != mod.uid)
+ struct cf_mod *old_cf;
+
+ old_cf = cgw_job_cf_mod(gwj);
+ if (old_cf->uid != mod->uid)
continue;
/* interfaces & filters must be identical */
- if (memcmp(&gwj->ccgw, &ccgw, sizeof(ccgw)))
- return -EINVAL;
+ if (memcmp(&gwj->ccgw, &ccgw, sizeof(ccgw))) {
+ err = -EINVAL;
+ goto out_free_cf;
+ }
- /* update modifications with disabled softirq & quit */
- local_bh_disable();
- memcpy(&gwj->mod, &mod, sizeof(mod));
- local_bh_enable();
+ rcu_assign_pointer(gwj->cf_mod, mod);
+ kfree_rcu_mightsleep(old_cf);
return 0;
}
}
/* ifindex == 0 is not allowed for job creation */
- if (!ccgw.src_idx || !ccgw.dst_idx)
- return -ENODEV;
+ if (!ccgw.src_idx || !ccgw.dst_idx) {
+ err = -ENODEV;
+ goto out_free_cf;
+ }
gwj = kmem_cache_alloc(cgw_cache, GFP_KERNEL);
- if (!gwj)
- return -ENOMEM;
+ if (!gwj) {
+ err = -ENOMEM;
+ goto out_free_cf;
+ }
gwj->handled_frames = 0;
gwj->dropped_frames = 0;
@@ -1118,7 +1144,7 @@ static int cgw_create_job(struct sk_buff *skb, struct nlmsghdr *nlh,
gwj->limit_hops = limhops;
/* insert already parsed information */
- memcpy(&gwj->mod, &mod, sizeof(mod));
+ RCU_INIT_POINTER(gwj->cf_mod, mod);
memcpy(&gwj->ccgw, &ccgw, sizeof(ccgw));
err = -ENODEV;
@@ -1152,9 +1178,11 @@ static int cgw_create_job(struct sk_buff *skb, struct nlmsghdr *nlh,
if (!err)
hlist_add_head_rcu(&gwj->list, &net->can.cgw_list);
out:
- if (err)
+ if (err) {
kmem_cache_free(cgw_cache, gwj);
-
+out_free_cf:
+ kfree(mod);
+ }
return err;
}
@@ -1214,19 +1242,22 @@ static int cgw_remove_job(struct sk_buff *skb, struct nlmsghdr *nlh,
/* remove only the first matching entry */
hlist_for_each_entry_safe(gwj, nx, &net->can.cgw_list, list) {
+ struct cf_mod *cf_mod;
+
if (gwj->flags != r->flags)
continue;
if (gwj->limit_hops != limhops)
continue;
+ cf_mod = cgw_job_cf_mod(gwj);
/* we have a match when uid is enabled and identical */
- if (gwj->mod.uid || mod.uid) {
- if (gwj->mod.uid != mod.uid)
+ if (cf_mod->uid || mod.uid) {
+ if (cf_mod->uid != mod.uid)
continue;
} else {
/* no uid => check for identical modifications */
- if (memcmp(&gwj->mod, &mod, sizeof(mod)))
+ if (memcmp(cf_mod, &mod, sizeof(mod)))
continue;
}
--
2.49.0
next reply other threads:[~2025-04-29 7:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-29 7:05 Sebastian Andrzej Siewior [this message]
2025-05-03 12:45 ` [PATCH v2] can: gw: fix RCU/BH usage in cgw_create_job() Marc Kleine-Budde
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