component: remove device from master match list on failed add

Calling component_add() may result in the completion of a set of
devices, which will try to bring up a master. In bringing the master
up, we populate its match array with the current set of children.

If binding any of the devices fails, component_add() itself will fail,
free the struct component entry, and return to the caller. The
now-freed entry is never removed from the master's match array, and
will later be used in a futile attempt to bind to freed memory.

Bring component_add's behaviour on failure to bring up a master into
line with component_del by removing the (to-be-freed) component from
the master's match array.

The specific case which broke was:
  - rockchip_drm_drv adds a component master
  - dwhdmi_rockchip adds a child component in probe (master incomplete)
  - rockchip_drm_vop adds two children in probe, which completes the
  - inside component_add, we try to bring up the master, having
    populated the master's match array, and fail with EPROBE_DEFER from
    dwhdmi_rockchip; we delete the putative component
  - rockchip_drm_vop's probe fails and returns EPROBE_DEFER
  - we later re-probe rockchip_drm_vop and add the component; the
    master is complete, so we attempt to bring it up again
  - walking the match array, we find the previous child, whose master
    pointer doesn't match (as it has been freed in the meantime)
  - rockchip_drm_vop probe fails, and will never be attempted again

Fixes: ffc30b74fd6d01588bd3fdebc3b1acc0857e6fc8
Signed-off-by: Daniel Stone <>
Cc: Russell King <>
Cc: Thierry Reding <>
Cc: Laurent Pinchart <>
Signed-off-by: Russell King <>
1 file changed