• Xiaotian Feng's avatar
    tty_audit: fix tty_audit_add_data live lock on audit disabled · 00bff392
    Xiaotian Feng authored
    The current tty_audit_add_data code:
    
            do {
                    size_t run;
    
                    run = N_TTY_BUF_SIZE - buf->valid;
                    if (run > size)
                            run = size;
                    memcpy(buf->data + buf->valid, data, run);
                    buf->valid += run;
                    data += run;
                    size -= run;
                    if (buf->valid == N_TTY_BUF_SIZE)
                            tty_audit_buf_push_current(buf);
            } while (size != 0);
    
    If the current buffer is full, kernel will then call tty_audit_buf_push_current
    to empty the buffer. But if we disabled audit at the same time, tty_audit_buf_push()
    returns immediately if audit_enabled is zero.  Without emptying the buffer.
    With obvious effect on tty_audit_add_data() that ends up spinning in that loop,
    copying 0 bytes at each iteration and attempting to push each time without any effect.
    Holding the lock all along.
    Suggested-by: default avatarAlexander Viro <aviro@redhat.com>
    Signed-off-by: default avatarXiaotian Feng <dfeng@redhat.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    00bff392
tty_audit.c 8.55 KB