linux-stable.git, branch v5.10.262 Linux kernel stable tree Linux 5.10.262 2026-07-30T10:56:00+00:00 Greg Kroah-Hartman gregkh@linuxfoundation.org 2026-07-30T10:56:00+00:00 065a677fad98698de04279ba2cb152a472ab8b1f Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
posix-cpu-timers: Prevent UAF caused by non-leader exec() race 2026-07-30T10:56:00+00:00 Thomas Gleixner tglx@kernel.org 2026-07-27T09:13:08+00:00 67aa823e3e8c229c6d374df79c804f6721cb83b6 commit 920f893f735e92ba3a1cd9256899a186b161928d upstream. Wongi and Jungwoo decoded and reported a non-leader exec() related race which can result in an UAF: sys_timer_delete() exec() posix_cpu_timer_del() // Observes old leader p = pid_task(pid, pid_type); de_thread() switch_leader(); release_task(old_leader) __exit_signal(old_leader) sighand = lock(old_leader, sighand); posix_cpu_timers*_exit(); sighand = lock_task_sighand(p) unhash_task(old_leader); sh = lock(p, sighand) old_leader->sighand = NULL; unlock(sighand); (p->sighand == NULL) unlock(sh) return NULL; // Returns without action if(!sighand) return 0; free_posix_timer(); This is "harmless" unless the deleted timer was armed and enqueued in p->signal because on exec() a TGID targeted timer is inherited. As sys_timer_delete() freed the underlying posix timer object run_posix_cpu_timers() or any timerqueue related add/delete operations on other timers will access the freed object's timerqueue node, which results in an UAF. There is a similar problem vs. posix_cpu_timer_set(). For regular posix timers it just transiently returns -ESRCH to user space, but for the use case in do_cpu_nanosleep() it's the same UAF just that the k_itimer is allocated on the stack. Also posix_cpu_timer_rearm() fails to rearm the timer, which means it stops to expire. While debating solutions Frederic pointed out another problem: posix_cpu_timer_del(tmr) __exit_signal(p) posix_cpu_timers*_exit(p); unhash_task(p); p->sighand = NULL; sh = lock_task_sighand(p) sighand = p->sighand; if (!sighand) return NULL; lock(sighand); if (!sh) WARN_ON_ONCE(timer_queued(tmr)); On weakly ordered architectures it is not guaranteed that posix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit() when p->sighand is observed as NULL, which means the WARN() can be a false positive. Solve these issues by: 1) Changing the store in __exit_signal() to smp_store_release(). 2) Adding a smp_acquire__after_ctrl_dep() into the !sighand path of lock_task_sighand(). 3) Creating a helper function for looking up the task and locking sighand which does not return when sighand == NULL. Instead it retries the task lookup and only if that fails it gives up. 4) Using that helper in the three affected functions. #1/#2 ensures that the reader side which observes sighand == NULL also observes all preceeding stores, i.e. the stores in posix_cpu_timers*_exit() and the ones in unhash_task(). #3 ensures that the above described non-leader exec() situation is handled gracefully. When the task lookup returns the old leader, but sighand == NULL then it retries. In the non-leader exec() case the subsequent task lookup will observe the new leader due to #1/#2. In normal exit() scenarios the subsequent lookup fails. When the task lookup fails, the function also checks whether the timer is still enqueued and issues a warning if that's the case. Unfortunately there is nothing which can be done about it, but as the task is already not longer visible the timer should not be accessed anymore. This check also requires memory ordering, which is not provided when the first lookup fails. To achieve that the check is preceeded by a smp_rmb() which pairs with the smp_wmb() in write_seqlock() in __exit_signal(). That ensures that the stores in posix_cpu_timers*_exit() are visible. The history of the non-leader exec() issue goes back to the early days of posix CPU timers, which stored a pointer to the group leader task in the timer. That obviously fails when a non-leader exec() switches the leader. commit e0a70217107e ("posix-cpu-timers: workaround to suppress the problems with mt exec") added a temporary workaround for that in 2010 which survived about 10 years. The fix for the workaround changed the task pointer to a pid pointer, but failed to see the subtle race described above. So the Fixes tag picks that commit, which seems to be halfways accurate. Thanks to Frederic Weissbecker, Oleg Nesterov and Peter Zijlstra for review, feedback and suggestions and to Wongi and Jungwoo for the excellent bug report and analysis! Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task") Reported-by: Wongi Lee <qw3rtyp0@gmail.com> Reported-by: Jungwoo Lee <jwlee2217@gmail.com> Signed-off-by: Thomas Gleixner <tglx@kernel.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org> 
commit 920f893f735e92ba3a1cd9256899a186b161928d upstream.

Wongi and Jungwoo decoded and reported a non-leader exec() related race
which can result in an UAF:

 sys_timer_delete()			exec()
   posix_cpu_timer_del()
   // Observes old leader
   p = pid_task(pid, pid_type);		de_thread()
   					  switch_leader();
					  release_task(old_leader)
					    __exit_signal(old_leader)
					      sighand = lock(old_leader, sighand);
					      posix_cpu_timers*_exit();
   sighand = lock_task_sighand(p)	      unhash_task(old_leader);
     sh = lock(p, sighand)	    	      old_leader->sighand = NULL;
					      unlock(sighand);
     (p->sighand == NULL)
	unlock(sh)
	return NULL;

   // Returns without action
   if(!sighand)
      return 0;
   free_posix_timer();

This is "harmless" unless the deleted timer was armed and enqueued in
p->signal because on exec() a TGID targeted timer is inherited.

As sys_timer_delete() freed the underlying posix timer object
run_posix_cpu_timers() or any timerqueue related add/delete operations on
other timers will access the freed object's timerqueue node, which results
in an UAF.

There is a similar problem vs. posix_cpu_timer_set(). For regular posix
timers it just transiently returns -ESRCH to user space, but for the use
case in do_cpu_nanosleep() it's the same UAF just that the k_itimer is
allocated on the stack.

Also posix_cpu_timer_rearm() fails to rearm the timer, which means it stops
to expire.

While debating solutions Frederic pointed out another problem:

   posix_cpu_timer_del(tmr)
					__exit_signal(p)
					  posix_cpu_timers*_exit(p);
					  unhash_task(p);
					  p->sighand = NULL;
     sh = lock_task_sighand(p)
        sighand = p->sighand;
	if (!sighand)
	    return NULL;
	lock(sighand);

     if (!sh)
	WARN_ON_ONCE(timer_queued(tmr));

On weakly ordered architectures it is not guaranteed that
posix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit()
when p->sighand is observed as NULL, which means the WARN() can be a false
positive.

Solve these issues by:

  1) Changing the store in __exit_signal() to smp_store_release().

  2) Adding a smp_acquire__after_ctrl_dep() into the !sighand path
     of lock_task_sighand().

  3) Creating a helper function for looking up the task and locking sighand
     which does not return when sighand == NULL. Instead it retries the
     task lookup and only if that fails it gives up.

  4) Using that helper in the three affected functions.

#1/#2 ensures that the reader side which observes sighand == NULL also
observes all preceeding stores, i.e. the stores in posix_cpu_timers*_exit()
and the ones in unhash_task().

#3 ensures that the above described non-leader exec() situation is handled
gracefully. When the task lookup returns the old leader, but sighand ==
NULL then it retries. In the non-leader exec() case the subsequent task
lookup will observe the new leader due to #1/#2. In normal exit() scenarios
the subsequent lookup fails.

When the task lookup fails, the function also checks whether the timer is
still enqueued and issues a warning if that's the case. Unfortunately there
is nothing which can be done about it, but as the task is already not
longer visible the timer should not be accessed anymore. This check also
requires memory ordering, which is not provided when the first lookup
fails. To achieve that the check is preceeded by a smp_rmb() which pairs
with the smp_wmb() in write_seqlock() in __exit_signal(). That ensures that
the stores in posix_cpu_timers*_exit() are visible.

The history of the non-leader exec() issue goes back to the early days of
posix CPU timers, which stored a pointer to the group leader task in the
timer. That obviously fails when a non-leader exec() switches the leader.
commit e0a70217107e ("posix-cpu-timers: workaround to suppress the problems
with mt exec") added a temporary workaround for that in 2010 which survived
about 10 years. The fix for the workaround changed the task pointer to a
pid pointer, but failed to see the subtle race described above. So the
Fixes tag picks that commit, which seems to be halfways accurate.

Thanks to Frederic Weissbecker, Oleg Nesterov and Peter Zijlstra for
review, feedback and suggestions and to Wongi and Jungwoo for the excellent
bug report and analysis!

Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Reported-by: Wongi Lee <qw3rtyp0@gmail.com>
Reported-by: Jungwoo Lee <jwlee2217@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux 5.10.261 2026-07-24T13:49:24+00:00 Greg Kroah-Hartman gregkh@linuxfoundation.org 2026-07-24T13:49:24+00:00 8ba4813938919857c129400fae2d80fcebb69b8f Link: https://lore.kernel.org/r/20260721152355.667394603@linuxfoundation.org Tested-by: Woody Suwalski <terraluna977@gmail.com> Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Dominique Martinet <dominique.martinet@atmark-techno.com> Link: https://lore.kernel.org/r/20260722142749.280611149@linuxfoundation.org Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Florian Fainelli <florian.fainelli@broadcom.com> Tested-by: Pavel Machek (CIP) <pavel@nabladev.com> Tested-by: Mark Brown <broonie@kernel.org> Tested-by: Barry K. Nathan <barryn@pobox.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Link: https://lore.kernel.org/r/20260721152355.667394603@linuxfoundation.org
Tested-by: Woody Suwalski <terraluna977@gmail.com>
Tested-by: Brett A C Sheffield <bacs@librecast.net>
Tested-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
Link: https://lore.kernel.org/r/20260722142749.280611149@linuxfoundation.org
Tested-by: Brett A C Sheffield <bacs@librecast.net>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Tested-by: Pavel Machek (CIP) <pavel@nabladev.com>
Tested-by: Mark Brown <broonie@kernel.org>
Tested-by: Barry K. Nathan <barryn@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tools/resolve_btfids: Emit warnings and patch zero id for missing symbols 2026-07-24T13:49:24+00:00 Hengqi Chen hengqi.chen@gmail.com 2021-07-27T13:25:31+00:00 791f3a533aab39e2eb95528c5e5e66450f75ef0c commit 5aad03685185b5133a28e1ee1d4e98d3fd3642a3 upstream. Kernel functions referenced by .BTF_ids may be changed from global to static and get inlined or get renamed/removed, and thus disappears from BTF. This causes kernel build failure when resolve_btfids do id patch for symbols in .BTF_ids in vmlinux. Update resolve_btfids to emit warning messages and patch zero id for missing symbols instead of aborting kernel build process. Suggested-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20210727132532.2473636-2-hengqi.chen@gmail.com Cc: "Barry K. Nathan" <barryn@pobox.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 5aad03685185b5133a28e1ee1d4e98d3fd3642a3 upstream.

Kernel functions referenced by .BTF_ids may be changed from global to static
and get inlined or get renamed/removed, and thus disappears from BTF.
This causes kernel build failure when resolve_btfids do id patch for symbols
in .BTF_ids in vmlinux. Update resolve_btfids to emit warning messages and
patch zero id for missing symbols instead of aborting kernel build process.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210727132532.2473636-2-hengqi.chen@gmail.com
Cc: "Barry K. Nathan" <barryn@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tools/resolve_btfids: Fix some error messages 2026-07-24T13:49:24+00:00 Brendan Jackman jackmanb@google.com 2020-12-03T10:22:34+00:00 0a9bd606628c63233e673e1a1e53e5ee224a2387 commit 22e8ebe35a2e30ee19e02c41cacc99c2f896bc4b upstream. Add missing newlines and fix polarity of strerror argument. Signed-off-by: Brendan Jackman <jackmanb@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Jiri Olsa <jolsa@redhat.com> Link: https://lore.kernel.org/bpf/20201203102234.648540-1-jackmanb@google.com Cc: "Barry K. Nathan" <barryn@pobox.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 22e8ebe35a2e30ee19e02c41cacc99c2f896bc4b upstream.

Add missing newlines and fix polarity of strerror argument.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/bpf/20201203102234.648540-1-jackmanb@google.com
Cc: "Barry K. Nathan" <barryn@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
perf/x86/amd/core: Always use the NMI latency mitigation 2026-07-24T13:49:24+00:00 Sandipan Das sandipan.das@amd.com 2026-06-01T14:58:46+00:00 252bc0450f3b25bdf328975e5f11a1865951b241 commit 73a4c02f94a98d94480c3e5c81450215a4da05ba upstream. Commit df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation to use a timestamp") fixed handling of late-arriving NMIs but limited the mitigation to processors having X86_FEATURE_PERFCTR_CORE. However, it is unclear if processors without this feature are also affected. When Mediated vPMU is enabled on affected hardware, it is also possible to bypass the fix inside KVM guests if X86_FEATURE_PERFCTR_CORE is removed from the guest CPUID (e.g. using "-cpu host,-perfctr-core" with QEMU). Hence, use the mitigation at all times. Fixes: df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation to use a timestamp") Signed-off-by: Sandipan Das <sandipan.das@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/29a3c970da289ab8f24282933bdb36545c0403e8.1780325517.git.sandipan.das@amd.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 73a4c02f94a98d94480c3e5c81450215a4da05ba upstream.

Commit df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation
to use a timestamp") fixed handling of late-arriving NMIs but limited
the mitigation to processors having X86_FEATURE_PERFCTR_CORE. However,
it is unclear if processors without this feature are also affected.
When Mediated vPMU is enabled on affected hardware, it is also possible
to bypass the fix inside KVM guests if X86_FEATURE_PERFCTR_CORE is
removed from the guest CPUID (e.g. using "-cpu host,-perfctr-core" with
QEMU). Hence, use the mitigation at all times.

Fixes: df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation to use a timestamp")
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/29a3c970da289ab8f24282933bdb36545c0403e8.1780325517.git.sandipan.das@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mld: fix suspicious RCU usage in __ipv6_dev_mc_dec() 2026-07-24T13:49:24+00:00 Taehee Yoo ap420073@gmail.com 2021-04-16T14:16:06+00:00 b58363bf680a389501a20a551038d47b464f819b commit aa8caa767e319bad34a82bfce7da1ed2b9c0ed6f upstream. __ipv6_dev_mc_dec() internally uses sleepable functions so that caller must not acquire atomic locks. But caller, which is addrconf_verify_rtnl() acquires rcu_read_lock_bh(). So this warning occurs in the __ipv6_dev_mc_dec(). Test commands: ip netns add A ip link add veth0 type veth peer name veth1 ip link set veth1 netns A ip link set veth0 up ip netns exec A ip link set veth1 up ip a a 2001:db8::1/64 dev veth0 valid_lft 2 preferred_lft 1 Splat looks like: ============================ WARNING: suspicious RCU usage 5.12.0-rc6+ #515 Not tainted ----------------------------- kernel/sched/core.c:8294 Illegal context switch in RCU-bh read-side critical section! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 4 locks held by kworker/4:0/1997: #0: ffff88810bd72d48 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x761/0x1440 #1: ffff888105c8fe00 ((addr_chk_work).work){+.+.}-{0:0}, at: process_one_work+0x795/0x1440 #2: ffffffffb9279fb0 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0xa/0x20 #3: ffffffffb8e30860 (rcu_read_lock_bh){....}-{1:2}, at: addrconf_verify_rtnl+0x23/0xc60 stack backtrace: CPU: 4 PID: 1997 Comm: kworker/4:0 Not tainted 5.12.0-rc6+ #515 Workqueue: ipv6_addrconf addrconf_verify_work Call Trace: dump_stack+0xa4/0xe5 ___might_sleep+0x27d/0x2b0 __mutex_lock+0xc8/0x13f0 ? lock_downgrade+0x690/0x690 ? __ipv6_dev_mc_dec+0x49/0x2a0 ? mark_held_locks+0xb7/0x120 ? mutex_lock_io_nested+0x1270/0x1270 ? lockdep_hardirqs_on_prepare+0x12c/0x3e0 ? _raw_spin_unlock_irqrestore+0x47/0x50 ? trace_hardirqs_on+0x41/0x120 ? __wake_up_common_lock+0xc9/0x100 ? __wake_up_common+0x620/0x620 ? memset+0x1f/0x40 ? netlink_broadcast_filtered+0x2c4/0xa70 ? __ipv6_dev_mc_dec+0x49/0x2a0 __ipv6_dev_mc_dec+0x49/0x2a0 ? netlink_broadcast_filtered+0x2f6/0xa70 addrconf_leave_solict.part.64+0xad/0xf0 ? addrconf_join_solict.part.63+0xf0/0xf0 ? nlmsg_notify+0x63/0x1b0 __ipv6_ifa_notify+0x22c/0x9c0 ? inet6_fill_ifaddr+0xbe0/0xbe0 ? lockdep_hardirqs_on_prepare+0x12c/0x3e0 ? __local_bh_enable_ip+0xa5/0xf0 ? ipv6_del_addr+0x347/0x870 ipv6_del_addr+0x3b1/0x870 ? addrconf_ifdown+0xfe0/0xfe0 ? rcu_read_lock_any_held.part.27+0x20/0x20 addrconf_verify_rtnl+0x8a9/0xc60 addrconf_verify_work+0xf/0x20 process_one_work+0x84c/0x1440 In order to avoid this problem, it uses rcu_read_unlock_bh() for a short time. RCU is used for avoiding freeing ifp(struct *inet6_ifaddr) while ifp is being used. But this will not be released even if rcu_read_unlock_bh() is used. Because before rcu_read_unlock_bh(), it uses in6_ifa_hold(ifp). So this is safe. Fixes: 63ed8de4be81 ("mld: add mc_lock for protecting per-interface mld data") Suggested-by: Eric Dumazet <edumazet@google.com> Reported-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Taehee Yoo <ap420073@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit aa8caa767e319bad34a82bfce7da1ed2b9c0ed6f upstream.

__ipv6_dev_mc_dec() internally uses sleepable functions so that caller
must not acquire atomic locks. But caller, which is addrconf_verify_rtnl()
acquires rcu_read_lock_bh().
So this warning occurs in the __ipv6_dev_mc_dec().

Test commands:
    ip netns add A
    ip link add veth0 type veth peer name veth1
    ip link set veth1 netns A
    ip link set veth0 up
    ip netns exec A ip link set veth1 up
    ip a a 2001:db8::1/64 dev veth0 valid_lft 2 preferred_lft 1

Splat looks like:
============================
WARNING: suspicious RCU usage
5.12.0-rc6+ #515 Not tainted
-----------------------------
kernel/sched/core.c:8294 Illegal context switch in RCU-bh read-side
critical section!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
4 locks held by kworker/4:0/1997:
 #0: ffff88810bd72d48 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at:
process_one_work+0x761/0x1440
 #1: ffff888105c8fe00 ((addr_chk_work).work){+.+.}-{0:0}, at:
process_one_work+0x795/0x1440
 #2: ffffffffb9279fb0 (rtnl_mutex){+.+.}-{3:3}, at:
addrconf_verify_work+0xa/0x20
 #3: ffffffffb8e30860 (rcu_read_lock_bh){....}-{1:2}, at:
addrconf_verify_rtnl+0x23/0xc60

stack backtrace:
CPU: 4 PID: 1997 Comm: kworker/4:0 Not tainted 5.12.0-rc6+ #515
Workqueue: ipv6_addrconf addrconf_verify_work
Call Trace:
 dump_stack+0xa4/0xe5
 ___might_sleep+0x27d/0x2b0
 __mutex_lock+0xc8/0x13f0
 ? lock_downgrade+0x690/0x690
 ? __ipv6_dev_mc_dec+0x49/0x2a0
 ? mark_held_locks+0xb7/0x120
 ? mutex_lock_io_nested+0x1270/0x1270
 ? lockdep_hardirqs_on_prepare+0x12c/0x3e0
 ? _raw_spin_unlock_irqrestore+0x47/0x50
 ? trace_hardirqs_on+0x41/0x120
 ? __wake_up_common_lock+0xc9/0x100
 ? __wake_up_common+0x620/0x620
 ? memset+0x1f/0x40
 ? netlink_broadcast_filtered+0x2c4/0xa70
 ? __ipv6_dev_mc_dec+0x49/0x2a0
 __ipv6_dev_mc_dec+0x49/0x2a0
 ? netlink_broadcast_filtered+0x2f6/0xa70
 addrconf_leave_solict.part.64+0xad/0xf0
 ? addrconf_join_solict.part.63+0xf0/0xf0
 ? nlmsg_notify+0x63/0x1b0
 __ipv6_ifa_notify+0x22c/0x9c0
 ? inet6_fill_ifaddr+0xbe0/0xbe0
 ? lockdep_hardirqs_on_prepare+0x12c/0x3e0
 ? __local_bh_enable_ip+0xa5/0xf0
 ? ipv6_del_addr+0x347/0x870
 ipv6_del_addr+0x3b1/0x870
 ? addrconf_ifdown+0xfe0/0xfe0
 ? rcu_read_lock_any_held.part.27+0x20/0x20
 addrconf_verify_rtnl+0x8a9/0xc60
 addrconf_verify_work+0xf/0x20
 process_one_work+0x84c/0x1440

In order to avoid this problem, it uses rcu_read_unlock_bh() for
a short time. RCU is used for avoiding freeing
ifp(struct *inet6_ifaddr) while ifp is being used. But this will
not be released even if rcu_read_unlock_bh() is used.
Because before rcu_read_unlock_bh(), it uses in6_ifa_hold(ifp).
So this is safe.

Fixes: 63ed8de4be81 ("mld: add mc_lock for protecting per-interface mld data")
Suggested-by: Eric Dumazet <edumazet@google.com>
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ipv6: mcast: remove one synchronize_net() barrier in ipv6_mc_down() 2026-07-24T13:49:24+00:00 Eric Dumazet edumazet@google.com 2024-02-09T15:30:56+00:00 bfd2f3c58ad86ad33db80515e6c3503e0414e44b commit 17ef8efc00b34918b966388b2af0993811895a8c upstream. As discussed in the past (commit 2d3916f31891 ("ipv6: fix skb drops in igmp6_event_query() and igmp6_event_report()")) I think the synchronize_net() call in ipv6_mc_down() is not needed. Under load, synchronize_net() can last between 200 usec and 5 ms. KASAN seems to agree as well. Fixes: f185de28d9ae ("mld: add new workqueues for process mld events") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Taehee Yoo <ap420073@gmail.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: David Ahern <dsahern@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 17ef8efc00b34918b966388b2af0993811895a8c upstream.

As discussed in the past (commit 2d3916f31891 ("ipv6: fix skb drops
in igmp6_event_query() and igmp6_event_report()")) I think the
synchronize_net() call in ipv6_mc_down() is not needed.

Under load, synchronize_net() can last between 200 usec and 5 ms.

KASAN seems to agree as well.

Fixes: f185de28d9ae ("mld: add new workqueues for process mld events")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Taehee Yoo <ap420073@gmail.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work 2026-07-24T13:49:24+00:00 Nikita Zhandarovich n.zhandarovich@fintech.ru 2024-01-17T17:21:02+00:00 75ddcd741d2a30696f5893bc71a9d28f4ef22311 commit 2e7ef287f07c74985f1bf2858bedc62bd9ebf155 upstream. idev->mc_ifc_count can be written over without proper locking. Originally found by syzbot [1], fix this issue by encapsulating calls to mld_ifc_stop_work() (and mld_gq_stop_work() for good measure) with mutex_lock() and mutex_unlock() accordingly as these functions should only be called with mc_lock per their declarations. [1] BUG: KCSAN: data-race in ipv6_mc_down / mld_ifc_work write to 0xffff88813a80c832 of 1 bytes by task 3771 on cpu 0: mld_ifc_stop_work net/ipv6/mcast.c:1080 [inline] ipv6_mc_down+0x10a/0x280 net/ipv6/mcast.c:2725 addrconf_ifdown+0xe32/0xf10 net/ipv6/addrconf.c:3949 addrconf_notify+0x310/0x980 notifier_call_chain kernel/notifier.c:93 [inline] raw_notifier_call_chain+0x6b/0x1c0 kernel/notifier.c:461 __dev_notify_flags+0x205/0x3d0 dev_change_flags+0xab/0xd0 net/core/dev.c:8685 do_setlink+0x9f6/0x2430 net/core/rtnetlink.c:2916 rtnl_group_changelink net/core/rtnetlink.c:3458 [inline] __rtnl_newlink net/core/rtnetlink.c:3717 [inline] rtnl_newlink+0xbb3/0x1670 net/core/rtnetlink.c:3754 rtnetlink_rcv_msg+0x807/0x8c0 net/core/rtnetlink.c:6558 netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2545 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6576 netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline] netlink_unicast+0x589/0x650 net/netlink/af_netlink.c:1368 netlink_sendmsg+0x66e/0x770 net/netlink/af_netlink.c:1910 ... write to 0xffff88813a80c832 of 1 bytes by task 22 on cpu 1: mld_ifc_work+0x54c/0x7b0 net/ipv6/mcast.c:2653 process_one_work kernel/workqueue.c:2627 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2700 worker_thread+0x525/0x730 kernel/workqueue.c:2781 ... Fixes: 2d9a93b4902b ("mld: convert from timer to delayed work") Reported-by: syzbot+a9400cabb1d784e49abf@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/000000000000994e09060ebcdffb@google.com/ Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru> Acked-by: Taehee Yoo <ap420073@gmail.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Hangbin Liu <liuhangbin@gmail.com> Link: https://lore.kernel.org/r/20240117172102.12001-1-n.zhandarovich@fintech.ru Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 2e7ef287f07c74985f1bf2858bedc62bd9ebf155 upstream.

idev->mc_ifc_count can be written over without proper locking.

Originally found by syzbot [1], fix this issue by encapsulating calls
to mld_ifc_stop_work() (and mld_gq_stop_work() for good measure) with
mutex_lock() and mutex_unlock() accordingly as these functions
should only be called with mc_lock per their declarations.

[1]
BUG: KCSAN: data-race in ipv6_mc_down / mld_ifc_work

write to 0xffff88813a80c832 of 1 bytes by task 3771 on cpu 0:
 mld_ifc_stop_work net/ipv6/mcast.c:1080 [inline]
 ipv6_mc_down+0x10a/0x280 net/ipv6/mcast.c:2725
 addrconf_ifdown+0xe32/0xf10 net/ipv6/addrconf.c:3949
 addrconf_notify+0x310/0x980
 notifier_call_chain kernel/notifier.c:93 [inline]
 raw_notifier_call_chain+0x6b/0x1c0 kernel/notifier.c:461
 __dev_notify_flags+0x205/0x3d0
 dev_change_flags+0xab/0xd0 net/core/dev.c:8685
 do_setlink+0x9f6/0x2430 net/core/rtnetlink.c:2916
 rtnl_group_changelink net/core/rtnetlink.c:3458 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3717 [inline]
 rtnl_newlink+0xbb3/0x1670 net/core/rtnetlink.c:3754
 rtnetlink_rcv_msg+0x807/0x8c0 net/core/rtnetlink.c:6558
 netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2545
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6576
 netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]
 netlink_unicast+0x589/0x650 net/netlink/af_netlink.c:1368
 netlink_sendmsg+0x66e/0x770 net/netlink/af_netlink.c:1910
 ...

write to 0xffff88813a80c832 of 1 bytes by task 22 on cpu 1:
 mld_ifc_work+0x54c/0x7b0 net/ipv6/mcast.c:2653
 process_one_work kernel/workqueue.c:2627 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2700
 worker_thread+0x525/0x730 kernel/workqueue.c:2781
 ...

Fixes: 2d9a93b4902b ("mld: convert from timer to delayed work")
Reported-by: syzbot+a9400cabb1d784e49abf@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/000000000000994e09060ebcdffb@google.com/
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Acked-by: Taehee Yoo <ap420073@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20240117172102.12001-1-n.zhandarovich@fintech.ru
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net: mld: fix reference count leak in mld_{query | report}_work() 2026-07-24T13:49:24+00:00 Taehee Yoo ap420073@gmail.com 2022-07-22T17:06:35+00:00 f0759634e491fb30ca5aa60d71a15ca7c24ecd69 commit 3e7d18b9dca388940a19cae30bfc1f76dccd8c28 upstream. mld_{query | report}_work() processes queued events. If there are too many events in the queue, it re-queue a work. And then, it returns without in6_dev_put(). But if queuing is failed, it should call in6_dev_put(), but it doesn't. So, a reference count leak would occur. THREAD0 THREAD1 mld_report_work() spin_lock_bh() if (!mod_delayed_work()) in6_dev_hold(); spin_unlock_bh() spin_lock_bh() schedule_delayed_work() spin_unlock_bh() Script to reproduce(by Hangbin Liu): ip netns add ns1 ip netns add ns2 ip netns exec ns1 sysctl -w net.ipv6.conf.all.force_mld_version=1 ip netns exec ns2 sysctl -w net.ipv6.conf.all.force_mld_version=1 ip -n ns1 link add veth0 type veth peer name veth0 netns ns2 ip -n ns1 link set veth0 up ip -n ns2 link set veth0 up for i in `seq 50`; do for j in `seq 100`; do ip -n ns1 addr add 2021:${i}::${j}/64 dev veth0 ip -n ns2 addr add 2022:${i}::${j}/64 dev veth0 done done modprobe -r veth ip -a netns del splat looks like: unregister_netdevice: waiting for veth0 to become free. Usage count = 2 leaked reference. ipv6_add_dev+0x324/0xec0 addrconf_notify+0x481/0xd10 raw_notifier_call_chain+0xe3/0x120 call_netdevice_notifiers+0x106/0x160 register_netdevice+0x114c/0x16b0 veth_newlink+0x48b/0xa50 [veth] rtnl_newlink+0x11a2/0x1a40 rtnetlink_rcv_msg+0x63f/0xc00 netlink_rcv_skb+0x1df/0x3e0 netlink_unicast+0x5de/0x850 netlink_sendmsg+0x6c9/0xa90 ____sys_sendmsg+0x76a/0x780 __sys_sendmsg+0x27c/0x340 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Tested-by: Hangbin Liu <liuhangbin@gmail.com> Fixes: f185de28d9ae ("mld: add new workqueues for process mld events") Signed-off-by: Taehee Yoo <ap420073@gmail.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 3e7d18b9dca388940a19cae30bfc1f76dccd8c28 upstream.

mld_{query | report}_work() processes queued events.
If there are too many events in the queue, it re-queue a work.
And then, it returns without in6_dev_put().
But if queuing is failed, it should call in6_dev_put(), but it doesn't.
So, a reference count leak would occur.

THREAD0				THREAD1
mld_report_work()
				spin_lock_bh()
				if (!mod_delayed_work())
					in6_dev_hold();
				spin_unlock_bh()
	spin_lock_bh()
	schedule_delayed_work()
	spin_unlock_bh()

Script to reproduce(by Hangbin Liu):
   ip netns add ns1
   ip netns add ns2
   ip netns exec ns1 sysctl -w net.ipv6.conf.all.force_mld_version=1
   ip netns exec ns2 sysctl -w net.ipv6.conf.all.force_mld_version=1

   ip -n ns1 link add veth0 type veth peer name veth0 netns ns2
   ip -n ns1 link set veth0 up
   ip -n ns2 link set veth0 up

   for i in `seq 50`; do
           for j in `seq 100`; do
                   ip -n ns1 addr add 2021:${i}::${j}/64 dev veth0
                   ip -n ns2 addr add 2022:${i}::${j}/64 dev veth0
           done
   done
   modprobe -r veth
   ip -a netns del

splat looks like:
 unregister_netdevice: waiting for veth0 to become free. Usage count = 2
 leaked reference.
  ipv6_add_dev+0x324/0xec0
  addrconf_notify+0x481/0xd10
  raw_notifier_call_chain+0xe3/0x120
  call_netdevice_notifiers+0x106/0x160
  register_netdevice+0x114c/0x16b0
  veth_newlink+0x48b/0xa50 [veth]
  rtnl_newlink+0x11a2/0x1a40
  rtnetlink_rcv_msg+0x63f/0xc00
  netlink_rcv_skb+0x1df/0x3e0
  netlink_unicast+0x5de/0x850
  netlink_sendmsg+0x6c9/0xa90
  ____sys_sendmsg+0x76a/0x780
  __sys_sendmsg+0x27c/0x340
  do_syscall_64+0x43/0x90
  entry_SYSCALL_64_after_hwframe+0x63/0xcd

Tested-by: Hangbin Liu <liuhangbin@gmail.com>
Fixes: f185de28d9ae ("mld: add new workqueues for process mld events")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>