[PATCH AUTOSEL 6.6 074/139] fbdev: efifb: Register sysfs groups through driver core

[PATCH AUTOSEL 6.6 074/139] fbdev: efifb: Register sysfs groups through driver core

[Sasha Levin]

From: Thomas Weißschuh <linux@weissschuh.net>

[ Upstream commit 95cdd538e0e5677efbdf8aade04ec098ab98f457 ]

The driver core can register and cleanup sysfs groups already.
Make use of that functionality to simplify the error handling and
cleanup.

Also avoid a UAF race during unregistering where the sysctl attributes
were usable after the info struct was freed.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/video/fbdev/efifb.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
index f9b4ddd592ce4..88ac24202a1ff 100644
--- a/drivers/video/fbdev/efifb.c
+++ b/drivers/video/fbdev/efifb.c
@@ -571,15 +571,10 @@ static int efifb_probe(struct platform_device *dev)
 		break;
 	}
 
-	err = sysfs_create_groups(&dev->dev.kobj, efifb_groups);
-	if (err) {
-		pr_err("efifb: cannot add sysfs attrs\n");
-		goto err_unmap;
-	}
 	err = fb_alloc_cmap(&info->cmap, 256, 0);
 	if (err < 0) {
 		pr_err("efifb: cannot allocate colormap\n");
-		goto err_groups;
+		goto err_unmap;
 	}
 
 	if (efifb_pci_dev)
@@ -603,8 +598,6 @@ static int efifb_probe(struct platform_device *dev)
 		pm_runtime_put(&efifb_pci_dev->dev);
 
 	fb_dealloc_cmap(&info->cmap);
-err_groups:
-	sysfs_remove_groups(&dev->dev.kobj, efifb_groups);
 err_unmap:
 	if (mem_flags & (EFI_MEMORY_UC | EFI_MEMORY_WC))
 		iounmap(info->screen_base);
@@ -624,12 +617,12 @@ static void efifb_remove(struct platform_device *pdev)
 
 	/* efifb_destroy takes care of info cleanup */
 	unregister_framebuffer(info);
-	sysfs_remove_groups(&pdev->dev.kobj, efifb_groups);
 }
 
 static struct platform_driver efifb_driver = {
 	.driver = {
 		.name = "efi-framebuffer",
+		.dev_groups = efifb_groups,
 	},
 	.probe = efifb_probe,
 	.remove_new = efifb_remove,
-- 
2.43.0

[PATCH AUTOSEL 6.6 075/139] fbdev: pxafb: Fix possible use after free in pxafb_task()

[Sasha Levin]

From: Kaixin Wang <kxwang23@m.fudan.edu.cn>

[ Upstream commit 4a6921095eb04a900e0000da83d9475eb958e61e ]

In the pxafb_probe function, it calls the pxafb_init_fbinfo function,
after which &fbi->task is associated with pxafb_task. Moreover,
within this pxafb_init_fbinfo function, the pxafb_blank function
within the &pxafb_ops struct is capable of scheduling work.

If we remove the module which will call pxafb_remove to make cleanup,
it will call unregister_framebuffer function which can call
do_unregister_framebuffer to free fbi->fb through
put_fb_info(fb_info), while the work mentioned above will be used.
The sequence of operations that may lead to a UAF bug is as follows:

CPU0                                                CPU1

                                   | pxafb_task
pxafb_remove                       |
unregister_framebuffer(info)       |
do_unregister_framebuffer(fb_info) |
put_fb_info(fb_info)               |
// free fbi->fb                    | set_ctrlr_state(fbi, state)
                                   | __pxafb_lcd_power(fbi, 0)
                                   | fbi->lcd_power(on, &fbi->fb.var)
                                   | //use fbi->fb

Fix it by ensuring that the work is canceled before proceeding
with the cleanup in pxafb_remove.

Note that only root user can remove the driver at runtime.

Signed-off-by: Kaixin Wang <kxwang23@m.fudan.edu.cn>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/video/fbdev/pxafb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/video/fbdev/pxafb.c b/drivers/video/fbdev/pxafb.c
index fa943612c4e2b..3a2427eb29f23 100644
--- a/drivers/video/fbdev/pxafb.c
+++ b/drivers/video/fbdev/pxafb.c
@@ -2403,6 +2403,7 @@ static void pxafb_remove(struct platform_device *dev)
 	info = &fbi->fb;
 
 	pxafb_overlay_exit(fbi);
+	cancel_work_sync(&fbi->task);
 	unregister_framebuffer(info);
 
 	pxafb_disable_controller(fbi);
-- 
2.43.0