From acde4003efc16480375543638484d8f13f2e99a3 Mon Sep 17 00:00:00 2001 From: Javier Martinez Canillas Date: Thu, 26 May 2022 21:47:52 +0200 Subject: [PATCH] video: fbdev: vesafb: Fix a use-after-free due early fb_info cleanup Commit b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove") fixed a use-after-free error due the vesafb driver freeing the fb_info in the .remove handler instead of doing it in .fb_destroy. This can happen if the .fb_destroy callback is executed after the .remove callback, since the former tries to access a pointer freed by the latter. But that change didn't take into account that another possible scenario is that .fb_destroy is called before the .remove callback. For example, if no process has the fbdev chardev opened by the time the driver is removed. If that's the case, fb_info will be freed when unregister_framebuffer() is called, making the fb_info pointer accessed in vesafb_remove() after that to no longer be valid. To prevent that, move the expression containing the info->par to happen before the unregister_framebuffer() function call. Fixes: b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove") Reported-by: Pascal Ernster Signed-off-by: Javier Martinez Canillas Tested-by: Pascal Ernster Signed-off-by: Helge Deller --- drivers/video/fbdev/vesafb.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c index e25e8de5ff67..929d4775cb4b 100644 --- a/drivers/video/fbdev/vesafb.c +++ b/drivers/video/fbdev/vesafb.c @@ -490,11 +490,12 @@ static int vesafb_remove(struct platform_device *pdev) { struct fb_info *info = platform_get_drvdata(pdev); - /* vesafb_destroy takes care of info cleanup */ - unregister_framebuffer(info); if (((struct vesafb_par *)(info->par))->region) release_region(0x3c0, 32); + /* vesafb_destroy takes care of info cleanup */ + unregister_framebuffer(info); + return 0; } -- 2.11.0