When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
race with an associated action.
Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:
0: mutex_lock() <-- holds the idr lock
0: rcu_read_lock()
0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)
0: mutex_unlock() <-- releases the idr lock
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index) <-- Action removed from IDR
1: mutex_unlock() <-- mutex released allowing us to delete the action
1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory
This patch fixes the race condition between NEWTFILTER and DELFILTER by
adding struct rcu_head to tc_action used in the deferral and introducing a
call_rcu() in the delete path to defer the final kfree().
Note: this is a revert of commit d7fb60b9ca ("net_sched: get rid of tcfa_rcu")
but also modernization/simplification to directly use kfree_rcu().
Let's illustrate the new restored code path:
0: rcu_read_lock()
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index)
1: mutex_unlock()
1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period
0: p = idr_find(idr, index)
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0
1: rcu_read_unlock() <-- release so freeing can run after grace period
After CPU1 calls idr_remove(), the object is no longer reachable through the IDR.
CPU0's subsequent idr_find() will return NULL, and even if it still held a
stale pointer, the immediate kfree() is now deferred until after the RCU grace
period, so no UAF can occur.
Fixes: d7fb60b9ca ("net_sched: get rid of tcfa_rcu")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reported-by: Kyle Zeng <kylebot@openai.com>
Tested-by: Victor Nogueira <victor@mojatatu.com>
Tested-by: syzbot@syzkaller.appspotmail.com
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Tested-by: Kyle Zeng <kylebot@openai.com>
Reviewed-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Link: https://patch.msgid.link/20260531160812.68020-1-jhs@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This was done entirely with mindless brute force, using
git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'
to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.
Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.
For the same reason the 'flex' versions will be done as a separate
conversion.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
tc_action_net_exit() got an rtnl exclusion in commit
a159d3c4b8 ("net_sched: acquire RTNL in tc_action_net_exit()")
Since then, commit 16af606739 ("net: sched: implement reference
counted action release") made this RTNL exclusion obsolete for
most cases.
Only tcf_action_offload_del() might still require it.
Move the rtnl locking into tcf_idrinfo_destroy() when
an offload action is found.
Most netns do not have actions, yet deleting them is adding a lot
of pressure on RTNL, which is for many the most contended mutex
in the kernel.
We are moving to a per-netns 'rtnl', so tc_action_net_exit()
will not be able to grab 'rtnl' a single time for a batch of netns.
Before the patch:
perf probe -a rtnl_lock
perf record -e probe:rtnl_lock -a /bin/bash -c 'unshare -n "/bin/true"; sleep 1'
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.305 MB perf.data (25 samples) ]
After the patch:
perf record -e probe:rtnl_lock -a /bin/bash -c 'unshare -n "/bin/true"; sleep 1'
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.304 MB perf.data (9 samples) ]
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vlad Buslov <vladbu@nvidia.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://patch.msgid.link/20250702071230.1892674-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
While developing the fix for the buffer sizing issue in [0], I noticed
that the kernel will happily accept a long list of actions for a filter,
and then just silently truncate that list down to a maximum of 32
actions.
That seems less than ideal, so this patch changes the action parsing to
return an error message and refuse to create the filter in this case.
This results in an error like:
# ip link add type veth
# tc qdisc replace dev veth0 root handle 1: fq_codel
# tc -echo filter add dev veth0 parent 1: u32 match u32 0 0 $(for i in $(seq 33); do echo action pedit munge ip dport set 22; done)
Error: Only 32 actions supported per filter.
We have an error talking to the kernel
Instead of just creating a filter with 32 actions and dropping the last
one.
This is obviously a change in UAPI. But seeing as creating more than 32
filters has never actually *worked*, it seems that returning an explicit
error is better, and any use cases that get broken by this were already
broken just in more subtle ways.
[0] https://lore.kernel.org/r/20250407105542.16601-1-toke@redhat.com
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://patch.msgid.link/20250409145523.164506-1-toke@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tcf_action_init() has logic for checking mismatches between action and
filter offload flags (skip_sw/skip_hw). AFAIU, this is intended to run
on the transition between the new tc_act_bind(flags) returning true (aka
now gets bound to classifier) and tc_act_bind(act->tcfa_flags) returning
false (aka action was not bound to classifier before). Otherwise, the
check is skipped.
For the case where an action is not standalone, but rather it was
created by a classifier and is bound to it, tcf_action_init() skips the
check entirely, and this means it allows mismatched flags to occur.
Taking the matchall classifier code path as an example (with mirred as
an action), the reason is the following:
1 | mall_change()
2 | -> mall_replace_hw_filter()
3 | -> tcf_exts_validate_ex()
4 | -> flags |= TCA_ACT_FLAGS_BIND;
5 | -> tcf_action_init()
6 | -> tcf_action_init_1()
7 | -> a_o->init()
8 | -> tcf_mirred_init()
9 | -> tcf_idr_create_from_flags()
10 | -> tcf_idr_create()
11 | -> p->tcfa_flags = flags;
12 | -> tc_act_bind(flags))
13 | -> tc_act_bind(act->tcfa_flags)
When invoked from tcf_exts_validate_ex() like matchall does (but other
classifiers validate their extensions as well), tcf_action_init() runs
in a call path where "flags" always contains TCA_ACT_FLAGS_BIND (set by
line 4). So line 12 is always true, and line 13 is always true as well.
No transition ever takes place, and the check is skipped.
The code was added in this form in commit c86e0209dc ("flow_offload:
validate flags of filter and actions"), but I'm attributing the blame
even earlier in that series, to when TCA_ACT_FLAGS_SKIP_HW and
TCA_ACT_FLAGS_SKIP_SW were added to the UAPI.
Following the development process of this change, the check did not
always exist in this form. A change took place between v3 [1] and v4 [2],
AFAIU due to review feedback that it doesn't make sense for action flags
to be different than classifier flags. I think I agree with that
feedback, but it was translated into code that omits enforcing this for
"classic" actions created at the same time with the filters themselves.
There are 3 more important cases to discuss. First there is this command:
$ tc qdisc add dev eth0 clasct
$ tc filter add dev eth0 ingress matchall skip_sw \
action mirred ingress mirror dev eth1
which should be allowed, because prior to the concept of dedicated
action flags, it used to work and it used to mean the action inherited
the skip_sw/skip_hw flags from the classifier. It's not a mismatch.
Then we have this command:
$ tc qdisc add dev eth0 clasct
$ tc filter add dev eth0 ingress matchall skip_sw \
action mirred ingress mirror dev eth1 skip_hw
where there is a mismatch and it should be rejected.
Finally, we have:
$ tc qdisc add dev eth0 clasct
$ tc filter add dev eth0 ingress matchall skip_sw \
action mirred ingress mirror dev eth1 skip_sw
where the offload flags coincide, and this should be treated the same as
the first command based on inheritance, and accepted.
[1]: https://lore.kernel.org/netdev/20211028110646.13791-9-simon.horman@corigine.com/
[2]: https://lore.kernel.org/netdev/20211118130805.23897-10-simon.horman@corigine.com/
Fixes: 7adc576512 ("flow_offload: add skip_hw and skip_sw to control if offload the action")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20241017161049.3570037-1-vladimir.oltean@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
We will remove rtnl_register() in favour of rtnl_register_many().
When it succeeds, rtnl_register_many() guarantees all rtnetlink types
in the passed array are supported, and there is no chance that a part
of message types is not supported.
Let's use rtnl_register_many() instead.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/20241014201828.91221-5-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Cross-merge networking fixes after downstream PR.
Conflicts:
drivers/net/ethernet/broadcom/bnxt/bnxt.c
1e7962114c ("bnxt_en: Restore PTP tx_avail count in case of skb_pad() error")
165f87691a ("bnxt_en: add timestamping statistics support")
No adjacent changes.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
syzbot found hanging tasks waiting on rtnl_lock [1]
A reproducer is available in the syzbot bug.
When a request to add multiple actions with the same index is sent, the
second request will block forever on the first request. This holds
rtnl_lock, and causes tasks to hang.
Return -EAGAIN to prevent infinite looping, while keeping documented
behavior.
[1]
INFO: task kworker/1:0:5088 blocked for more than 143 seconds.
Not tainted 6.9.0-rc4-syzkaller-00173-g3cdb45594619 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:0 state:D stack:23744 pid:5088 tgid:5088 ppid:2 flags:0x00004000
Workqueue: events_power_efficient reg_check_chans_work
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5409 [inline]
__schedule+0xf15/0x5d00 kernel/sched/core.c:6746
__schedule_loop kernel/sched/core.c:6823 [inline]
schedule+0xe7/0x350 kernel/sched/core.c:6838
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6895
__mutex_lock_common kernel/locking/mutex.c:684 [inline]
__mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752
wiphy_lock include/net/cfg80211.h:5953 [inline]
reg_leave_invalid_chans net/wireless/reg.c:2466 [inline]
reg_check_chans_work+0x10a/0x10e0 net/wireless/reg.c:2481
Fixes: 0190c1d452 ("net: sched: atomically check-allocate action")
Reported-by: syzbot+b87c222546179f4513a7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b87c222546179f4513a7
Signed-off-by: David Ruth <druth@chromium.org>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/r/20240614190326.1349786-1-druth@chromium.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
The cls_,sch_,act_ modules may be loaded lazily during network
configuration but without user's awareness and control.
Switch the lazy loading from canonical module names to a module alias.
This allows finer control over lazy loading, the precedent from
commit 7f78e03513 ("fs: Limit sys_mount to only request filesystem
modules.") explains it already:
Using aliases means user space can control the policy of which
filesystem^W net/sched modules are auto-loaded by editing
/etc/modprobe.d/*.conf with blacklist and alias directives.
Allowing simple, safe, well understood work-arounds to known
problematic software.
By default, nothing changes. However, if a specific module is
blacklisted (its canonical name), it won't be modprobe'd when requested
under its alias (i.e. kernel auto-loading). It would appear as if the
given module was unknown.
The module can still be loaded under its canonical name, which is an
explicit (privileged) user action.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240201130943.19536-4-mkoutny@suse.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Instead of using two bools derived from a flags passed as arguments to
the parent function of tc_action_load_ops, just pass the flags itself
to tc_action_load_ops to simplify its parameters.
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Bound actions always return '0' and as of today we rely on '0'
being returned in order to properly skip bound actions in
tcf_idr_insert_many. In order to further improve maintainability,
introduce the ACT_P_BOUND return code.
Actions are updated to return 'ACT_P_BOUND' instead of plain '0'.
tcf_idr_insert_many is then updated to check for 'ACT_P_BOUND'.
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/r/20231229132642.1489088-1-pctammela@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Continue expanding Daniel's patch by adding new skb drop reasons that
are idiosyncratic to TC.
More specifically:
- SKB_DROP_REASON_TC_COOKIE_ERROR: An error occurred whilst
processing a tc ext cookie.
- SKB_DROP_REASON_TC_CHAIN_NOTFOUND: tc chain lookup failed.
- SKB_DROP_REASON_TC_RECLASSIFY_LOOP: tc exceeded max reclassify loop
iterations
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Move drop_reason from struct tcf_result to skb cb - more specifically to
struct tc_skb_cb. With that, we'll be able to also set the drop reason for
the remaining qdiscs (aside from clsact) that do not have access to
tcf_result when time comes to set the skb drop reason.
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
tcf_idr_insert_many will replace the allocated -EBUSY pointer in
tcf_idr_check_alloc with the real action pointer, exposing it
to all operations. This operation is only needed when the action pointer
is created (ACT_P_CREATED). For actions which are bound to (returned 0),
the pointer already resides in the idr making such operation a nop.
Even though it's a nop, it's still not a cheap operation as internally
the idr code walks the idr and then does a replace on the appropriate slot.
So if the action was bound, better skip the idr replace entirely.
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Link: https://lore.kernel.org/r/20231211181807.96028-3-pctammela@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Instead of relying only on the idrinfo->lock mutex for
bind/alloc logic, rely on a combination of rcu + mutex + atomics
to better scale the case where multiple rtnl-less filters are
binding to the same action object.
Action binding happens when an action index is specified explicitly and
an action exists which such index exists. Example:
tc actions add action drop index 1
tc filter add ... matchall action drop index 1
tc filter add ... matchall action drop index 1
tc filter add ... matchall action drop index 1
tc filter ls ...
filter protocol all pref 49150 matchall chain 0 filter protocol all pref 49150 matchall chain 0 handle 0x1
not_in_hw
action order 1: gact action drop
random type none pass val 0
index 1 ref 4 bind 3
filter protocol all pref 49151 matchall chain 0 filter protocol all pref 49151 matchall chain 0 handle 0x1
not_in_hw
action order 1: gact action drop
random type none pass val 0
index 1 ref 4 bind 3
filter protocol all pref 49152 matchall chain 0 filter protocol all pref 49152 matchall chain 0 handle 0x1
not_in_hw
action order 1: gact action drop
random type none pass val 0
index 1 ref 4 bind 3
When no index is specified, as before, grab the mutex and allocate
in the idr the next available id. In this version, as opposed to before,
it's simplified to store the -EBUSY pointer instead of the previous
alloc + replace combination.
When an index is specified, rely on rcu to find if there's an object in
such index. If there's none, fallback to the above, serializing on the
mutex and reserving the specified id. If there's one, it can be an -EBUSY
pointer, in which case we just try again until it's an action, or an action.
Given the rcu guarantees, the action found could be dead and therefore
we need to bump the refcount if it's not 0, handling the case it's
in fact 0.
As bind and the action refcount are already atomics, these increments can
happen without the mutex protection while many tcf_idr_check_alloc race
to bind to the same action instance.
In case binding encounters a parallel delete or add, it will return
-EAGAIN in order to try again. Both filter and action apis already
have the retry machinery in-place. In case it's an unlocked filter it
retries under the rtnl lock.
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Link: https://lore.kernel.org/r/20231211181807.96028-2-pctammela@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
