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Gavrilov Ilia
0b9130247f
syzbot reported a memory leak in nr_create() [0]. Commit409db27e3a("netrom: Fix use-after-free of a listening socket.") added sock_hold() to the nr_heartbeat_expiry() function, where a) a socket has a SOCK_DESTROY flag or b) a listening socket has a SOCK_DEAD flag. But in the case "a," when the SOCK_DESTROY flag is set, the file descriptor has already been closed and the nr_release() function has been called. So it makes no sense to hold the reference count because no one will call another nr_destroy_socket() and put it as in the case "b." nr_connect nr_establish_data_link nr_start_heartbeat nr_release switch (nr->state) case NR_STATE_3 nr->state = NR_STATE_2 sock_set_flag(sk, SOCK_DESTROY); nr_rx_frame nr_process_rx_frame switch (nr->state) case NR_STATE_2 nr_state2_machine() nr_disconnect() nr_sk(sk)->state = NR_STATE_0 sock_set_flag(sk, SOCK_DEAD) nr_heartbeat_expiry switch (nr->state) case NR_STATE_0 if (sock_flag(sk, SOCK_DESTROY) || (sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_DEAD))) sock_hold() // ( !!! ) nr_destroy_socket() To fix the memory leak, let's call sock_hold() only for a listening socket. Found by InfoTeCS on behalf of Linux Verification Center (linuxtesting.org) with Syzkaller. [0]: https://syzkaller.appspot.com/bug?extid=d327a1f3b12e1e206c16 Reported-by: syzbot+d327a1f3b12e1e206c16@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d327a1f3b12e1e206c16 Fixes:409db27e3a("netrom: Fix use-after-free of a listening socket.") Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.