• R
    net: fix multithreaded signal handling in unix recv routines · b3ca9b02
    Rainer Weikusat 提交于
    The unix_dgram_recvmsg and unix_stream_recvmsg routines in
    net/af_unix.c utilize mutex_lock(&u->readlock) calls in order to
    serialize read operations of multiple threads on a single socket. This
    implies that, if all n threads of a process block in an AF_UNIX recv
    call trying to read data from the same socket, one of these threads
    will be sleeping in state TASK_INTERRUPTIBLE and all others in state
    TASK_UNINTERRUPTIBLE. Provided that a particular signal is supposed to
    be handled by a signal handler defined by the process and that none of
    this threads is blocking the signal, the complete_signal routine in
    kernel/signal.c will select the 'first' such thread it happens to
    encounter when deciding which thread to notify that a signal is
    supposed to be handled and if this is one of the TASK_UNINTERRUPTIBLE
    threads, the signal won't be handled until the one thread not blocking
    on the u->readlock mutex is woken up because some data to process has
    arrived (if this ever happens). The included patch fixes this by
    changing mutex_lock to mutex_lock_interruptible and handling possible
    error returns in the same way interruptions are handled by the actual
    receive-code.
    Signed-off-by: NRainer Weikusat <rweikusat@mobileactivedefense.com>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    b3ca9b02
af_unix.c 54.1 KB