• Marcelo Ricardo Leitner's avatar
    sctp: deny peeloff operation on asocs with threads sleeping on it · 35b9d61e
    Marcelo Ricardo Leitner authored
    commit dfcb9f4f upstream.
    
    commit 2dcab598 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
    attempted to avoid a BUG_ON call when the association being used for a
    sendmsg() is blocked waiting for more sndbuf and another thread did a
    peeloff operation on such asoc, moving it to another socket.
    
    As Ben Hutchings noticed, then in such case it would return without
    locking back the socket and would cause two unlocks in a row.
    
    Further analysis also revealed that it could allow a double free if the
    application managed to peeloff the asoc that is created during the
    sendmsg call, because then sctp_sendmsg() would try to free the asoc
    that was created only for that call.
    
    This patch takes another approach. It will deny the peeloff operation
    if there is a thread sleeping on the asoc, so this situation doesn't
    exist anymore. This avoids the issues described above and also honors
    the syscalls that are already being handled (it can be multiple sendmsg
    calls).
    
    Joint work with Xin Long.
    
    Fixes: 2dcab598 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
    Cc: Alexander Popov <alex.popov@linux.com>
    Cc: Ben Hutchings <ben@decadent.org.uk>
    Signed-off-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Signed-off-by: default avatarXin Long <lucien.xin@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    35b9d61e
socket.c 219 KB