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net: add missing ref_tracker_dir_exit() to net_passive_dec()

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I found that trying to read /sys/kernel/debug/ref_tracker/* causes NULL
pointer dereference crash when alloc_netdev_mqs() via unshare() returned
NULL, for commit 9ba74e6c9e ("net: add networking namespace refcount
tracker") added ref_tracker_dir_exit(&net->refcnt_tracker) to only
__put_net() path whereas commit 65b584f536 ("ref_tracker: automatically
register a file in debugfs for a ref_tracker_dir") added
ref_tracker_dir_debugfs() to ref_tracker_dir_init() path.

Since preinit_net() calls ref_tracker_dir_init(&net->refcnt_tracker) and
ref_tracker_dir_init(&net->notrefcnt_tracker), we need to make sure that
both ref_tracker_dir_exit(&net->refcnt_tracker) and
ref_tracker_dir_exit(&net->notrefcnt_tracker) are called before
net_passive_dec() schedules for kmem_cache_free() via net_complete_free().

ref_tracker_dir_exit(&net->refcnt_tracker) is called via put_net() when
ns_ref_put() returned true. But put_net() is not called when copy_net_ns()
fails. Therefore, call ref_tracker_dir_exit() from net_passive_dec() if
put_net() is not yet called.

Link: https://sashiko.dev/#/patchset/b06ce35d-e7bc-47a5-8e0a-e82be7e4dd08%40I-love.SAKURA.ne.jp
Fixes: 9ba74e6c9e ("net: add networking namespace refcount tracker")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://patch.msgid.link/64254d80-9248-466c-8108-95f43bd71117@I-love.SAKURA.ne.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Tetsuo Handa 2026-08-17 23:08:15 +09:00 • committed by Jakub Kicinski
commit f85dc137aa
1 changed files with 4 additions and 0 deletions
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