media: v4l2-core: Avoid the dangling pointer in v4l2_fh_release

Yunlongs · gregkh · commit eec7de8ef2d7 · 2021-07-20T16:22:32.000+02:00
[ Upstream commit 7dd0c9e547b6924e18712b6b51aa3cba1896ee2c ] A use after free bug caused by the dangling pointer filp->privitate_data in v4l2_fh_release. See https://lore.kernel.org/patchwork/patch/1419058/. My patch sets the dangling pointer to NULL to provide robust. Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/media/v4l2-core/v4l2-fh.c b/drivers/media/v4l2-core/v4l2-fh.c
@@ -107,6 +107,7 @@ int v4l2_fh_release(struct file *filp)
 		v4l2_fh_del(fh);
 		v4l2_fh_exit(fh);
 		kfree(fh);
+		filp->private_data = NULL;
 	}
 	return 0;
 }

Original file line number	Diff line number	Diff line change
`@@ -107,6 +107,7 @@ int v4l2_fh_release(struct file *filp)`
`107`	`107`	`v4l2_fh_del(fh);`
`108`	`108`	`v4l2_fh_exit(fh);`
`109`	`109`	`kfree(fh);`
	`110`	`+ filp->private_data = NULL;`
`110`	`111`	`}`
`111`	`112`	`return 0;`
`112`	`113`	`}`