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[ Upstream commitf29ccaa07c] syzbot reported a refcount warning [1] caused by calling get_net() on a network namespace that is being destroyed (refcount=0). This happens when a TIPC discovery timer fires during network namespace cleanup. The recently added get_net() call in commite279024617("net/tipc: fix slab-use-after-free Read in tipc_aead_encrypt_done") attempts to hold a reference to the network namespace. However, if the namespace is already being destroyed, its refcount might be zero, leading to the use-after-free warning. Replace get_net() with maybe_get_net(), which safely checks if the refcount is non-zero before incrementing it. If the namespace is being destroyed, return -ENODEV early, after releasing the bearer reference. [1]: https://lore.kernel.org/all/68342b55.a70a0220.253bc2.0091.GAE@google.com/T/#m12019cf9ae77e1954f666914640efa36d52704a2 Reported-by: syzbot+f0c4a4aba757549ae26c@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68342b55.a70a0220.253bc2.0091.GAE@google.com/T/#m12019cf9ae77e1954f666914640efa36d52704a2 Fixes:e279024617("net/tipc: fix slab-use-after-free Read in tipc_aead_encrypt_done") Signed-off-by: Charalampos Mitrodimas <charmitro@posteo.net> Reviewed-by: Tung Nguyen <tung.quang.nguyen@est.tech> Link: https://patch.msgid.link/20250527-net-tipc-warning-v2-1-df3dc398a047@posteo.net Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>