From: Peter Wu peter@lekensteyn.nl
[ Upstream commit 00eb5b0da8d27b3c944bfc959c3344d665caae26 ]
After drm_fb_helper_fbdev_setup calls drm_fb_helper_init, "dev->fb_helper" will be initialized (and thus drm_fb_helper_fini will have some effect). After that, drm_fb_helper_initial_config is called which may call the "fb_probe" driver callback.
This driver callback may call drm_fb_helper_defio_init (as is done by drm_fb_helper_generic_probe) or set a framebuffer (as is done by bochs) as documented. These are normally cleaned up on exit by drm_fb_helper_fbdev_teardown which also calls drm_fb_helper_fini.
If an error occurs after "fb_probe", but before setup is complete, then calling just drm_fb_helper_fini will leak resources. This was triggered by df2052cc922 ("bochs: convert to drm_fb_helper_fbdev_setup/teardown"):
[ 50.008030] bochsdrmfb: enable CONFIG_FB_LITTLE_ENDIAN to support this framebuffer [ 50.009436] bochs-drm 0000:00:02.0: [drm:drm_fb_helper_fbdev_setup] *ERROR* fbdev: Failed to set configuration (ret=-38) [ 50.011456] [drm] Initialized bochs-drm 1.0.0 20130925 for 0000:00:02.0 on minor 2 [ 50.013604] WARNING: CPU: 1 PID: 1 at drivers/gpu/drm/drm_mode_config.c:477 drm_mode_config_cleanup+0x280/0x2a0 [ 50.016175] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G T 4.20.0-rc7 #1 [ 50.017732] EIP: drm_mode_config_cleanup+0x280/0x2a0 ... [ 50.023155] Call Trace: [ 50.023155] ? bochs_kms_fini+0x1e/0x30 [ 50.023155] ? bochs_unload+0x18/0x40
This can be reproduced with QEMU and CONFIG_FB_LITTLE_ENDIAN=n.
Link: https://lkml.kernel.org/r/20181221083226.GI23332@shao2-debian Link: https://lkml.kernel.org/r/20181223004315.GA11455@al Fixes: 8741216396b2 ("drm/fb-helper: Add drm_fb_helper_fbdev_setup/teardown()") Reported-by: kernel test robot rong.a.chen@intel.com Cc: Noralf Trønnes noralf@tronnes.org Signed-off-by: Peter Wu peter@lekensteyn.nl Reviewed-by: Noralf Trønnes noralf@tronnes.org Signed-off-by: Noralf Trønnes noralf@tronnes.org Link: https://patchwork.freedesktop.org/patch/msgid/20181223005507.28328-1-peter@l... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/drm_fb_helper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 70fc8e356b18..edd8cb497f3b 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -2891,7 +2891,7 @@ int drm_fb_helper_fbdev_setup(struct drm_device *dev, return 0;
err_drm_fb_helper_fini: - drm_fb_helper_fini(fb_helper); + drm_fb_helper_fbdev_teardown(dev);
return ret; }