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Eric Dumazet
23c53269f2
Jaeyoung Chung and Eulgyu Kim reported a slab-use-after-free read
in slip_receive_buf() when racing against tty hangup.
tty_ldisc_hangup() calls ld->ops->hangup() while holding only
a read lock on tty->ldisc_sem (via tty_ldisc_ref()).
Because slip_hangup() simply called slip_close(), it ran concurrently
with reader functions such as slip_receive_buf().
slip_close() unregisters and frees the net device and its private
struct slip, causing concurrent reader threads in slip_receive_buf()
to dereference freed memory.
Line discipline close() is already guaranteed to be called under
the write lock of tty->ldisc_sem during hangup processing
(in tty_ldisc_reinit() or tty_ldisc_kill()).
Remove slip_hangup() so teardown is serialized cleanly by slip_close().
Fixes: 5342b77c41 ("slip: Clean up create and destroy")
Reported-by: Jaeyoung Chung <jjy600901@snu.ac.kr>
Reported-by: Eulgyu Kim <eulgyukim@snu.ac.kr>
Closes: https://lore.kernel.org/netdev/20260825150655.1450271-1-jjy600901@snu.ac.kr/
Cc: Qingfang Deng <qingfang.deng@linux.dev>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260826105238.3323436-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>