• Jan Beulich's avatar
    xen/hypercall: fix hypercall fallback code for very old hypervisors · cf47a83f
    Jan Beulich authored
    While copying the argument structures in HYPERVISOR_event_channel_op()
    and HYPERVISOR_physdev_op() into the local variable is sufficiently
    safe even if the actual structure is smaller than the container one,
    copying back eventual output values the same way isn't: This may
    collide with on-stack variables (particularly "rc") which may change
    between the first and second memcpy() (i.e. the second memcpy() could
    discard that change).
    Move the fallback code into out-of-line functions, and handle all of
    the operations known by this old a hypervisor individually: Some don't
    require copying back anything at all, and for the rest use the
    individual argument structures' sizes rather than the container's.
    Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: default avatarJan Beulich <jbeulich@suse.com>
    [v2: Reduce #define/#undef usage in HYPERVISOR_physdev_op_compat().]
    [v3: Fix compile errors when modules use said hypercalls]
    [v4: Add xen_ prefix to the HYPERCALL_..]
    [v5: Alter the name and only EXPORT_SYMBOL_GPL one of them]
    Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
fallback.c 1.49 KB