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can: gw: fix RCU/BH usage in cgw_create_job()

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[ Upstream commit 511e64e13d8cc72853275832e3f372607466c18c ]

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
description 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: dd895d7f21 ("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>
Link: https://patch.msgid.link/20250429070555.cs-7b_eZ@linutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Oliver Hartkopp
2025-04-29 09:05:55 +02:00
committed by Greg Kroah-Hartman
parent 3455e6394f
commit 42b7a7c962
1 changed files with 91 additions and 60 deletions
Download Patch File Download Diff File Expand all files Collapse all files

151
net/can/gw.c
View File

@@ -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;
}