Currently N_HDLC line discipline uses a self-made singly linked list for
data buffers and has n_hdlc.tbuf pointer for buffer retransmitting after
an error.
The commit be10eb7589337e5defbe214dae038a53dd21add8
("tty: n_hdlc add buffer flushing") introduced racy access to n_hdlc.tbuf.
After tx error concurrent flush_tx_queue() and n_hdlc_send_frames() can put
one data buffer to tx_free_buf_list twice. That causes double free in
n_hdlc_release().
Let's use standard kernel linked list and get rid of n_hdlc.tbuf:
in case of tx error put current data buffer after the head of tx_buf_list.
Signed-off-by: Alexander Popov <email address hidden>
CVE-2017-2636
Signed-off-by: Stefan Bader <email address hidden>
The class of 4 n_hdls buf locks is the same because a single function
n_hdlc_buf_list_init is used to init all the locks. But since
flush_tx_queue takes n_hdlc->tx_buf_list.spinlock and then calls
n_hdlc_buf_put which takes n_hdlc->tx_free_buf_list.spinlock, lockdep
emits a warning:
=============================================
[ INFO: possible recursive locking detected ]
4.3.0-25.g91e30a7-default #1 Not tainted
---------------------------------------------
a.out/1248 is trying to acquire lock:
(&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fd020>] n_hdlc_buf_put+0x20/0x60 [n_hdlc]
but task is already holding lock:
(&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fdc07>] n_hdlc_tty_ioctl+0x127/0x1d0 [n_hdlc]
other info that might help us debug this:
Possible unsafe locking scenario:
Signed-off-by: Stefan Bader <email address hidden>
4feb04a...
by
Andrey Konovalov <email address hidden>
dccp: fix freeing skb too early for IPV6_RECVPKTINFO
In the current DCCP implementation an skb for a DCCP_PKT_REQUEST packet
is forcibly freed via __kfree_skb in dccp_rcv_state_process if
dccp_v6_conn_request successfully returns.
However, if IPV6_RECVPKTINFO is set on a socket, the address of the skb
is saved to ireq->pktopts and the ref count for skb is incremented in
dccp_v6_conn_request, so skb is still in use. Nevertheless, it gets freed
in dccp_rcv_state_process.
Fix by calling consume_skb instead of doing goto discard and therefore
calling __kfree_skb.
Similar fixes for TCP:
fb7e2399ec17f1004c0e0ccfd17439f8759ede01 [TCP]: skb is unexpectedly freed.
0aea76d35c9651d55bbaf746e7914e5f9ae5a25d tcp: SYN packets are now
simply consumed
Signed-off-by: Andrey Konovalov <email address hidden>
Acked-by: Eric Dumazet <email address hidden>
Signed-off-by: David S. Miller <email address hidden>
In 19be0eaff ("mm: remove gup_flags FOLL_WRITE games from __get_user_pages()"),
the mm code was changed from unsetting FOLL_WRITE after a COW was resolved to
setting the (newly introduced) FOLL_COW instead. Simultaneously, the check in
gup.c was updated to still allow writes with FOLL_FORCE set if FOLL_COW had
also been set. However, a similar check in huge_memory.c was forgotten. As a
result, remote memory writes to ro regions of memory backed by transparent huge
pages cause an infinite loop in the kernel (handle_mm_fault sets FOLL_COW and
returns 0 causing a retry, but follow_trans_huge_pmd bails out immidiately
because `(flags & FOLL_WRITE) && !pmd_write(*pmd)` is true. While in this
state the process is stil SIGKILLable, but little else works (e.g. no ptrace
attach, no other signals). This is easily reproduced with the following
code (assuming thp are set to always):
Fix this by updating follow_trans_huge_pmd in huge_memory.c analogously to
the update in gup.c in the original commit. The same pattern exists in
follow_devmap_pmd. However, we should not be able to reach that check
with FOLL_COW set, so add WARN_ONCE to make sure we notice if we ever
do.
Signed-off-by: Keno Fischer <email address hidden>
Acked-by: Kirill A. Shutemov <email address hidden>
Acked-by: Michal Hocko <email address hidden>
Tested-by: David Rientjes <email address hidden>
Signed-off-by: Joseph Salisbury <email address hidden>
Acked-by: Stefan Bader <email address hidden>
Acked-by: Tim Gardner <email address hidden>
Signed-off-by: Thadeu Lima de Souza Cascardo <email address hidden>