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Pei XiaoandGreg Kroah-Hartman
7d3a708af7
The "removed" flag check in each tty op has a TOCTOU race with __ipoctal_remove(): the device could be removed between the flag check and the subsequent access to hardware resources (channel registers via iowrite8, or xmit_buf in write_tty). Close this race by introducing a read-write semaphore (remove_sem). The tty ops acquire the read lock via guard(rwsem_read) for the full duration of the operation, while __ipoctal_remove() acquires the write lock via scoped_guard(rwsem_write) when setting the removed flag. This ensures that once removed is true, no in-flight tty op can still be accessing resources that are about to be freed by the remove path. Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn> Link: https://patch.msgid.link/fbce75010a0f0a3a3709a5e06fd0ffd19ca0a0ed.1782870760.git.xiaopei01@kylinos.cn Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>