linux-kernel - [PATCH v2] video: hyperv_fb: Fix a double free in hvfb

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Date:   Wed, 24 Mar 2021 03:37:24 -0700
From:   Lv Yunlong <lyl2019@...l.ustc.edu.cn>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org
Cc:     linux-hyperv@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Subject: [PATCH v2] video: hyperv_fb: Fix a double free in hvfb_probe

In function hvfb_probe in hyperv_fb.c, it calls hvfb_getmem(hdev, info)
and return err when info->apertures is freed.

In the error1 label of hvfb_probe, info->apertures will be freed for the
second time in framebuffer_release(info).

My patch removes all kfree(info->apertures) instead of set info->apertures
to NULL. It is because that let framebuffer_release() handle freeing the
memory flows the fbdev pattern, and less code overall.

Signed-off-by: Lv Yunlong <lyl2019@...l.ustc.edu.cn>
---
 drivers/video/fbdev/hyperv_fb.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
index c8b0ae676809..4dc9077dd2ac 100644
--- a/drivers/video/fbdev/hyperv_fb.c
+++ b/drivers/video/fbdev/hyperv_fb.c
@@ -1031,7 +1031,6 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 			PCI_DEVICE_ID_HYPERV_VIDEO, NULL);
 		if (!pdev) {
 			pr_err("Unable to find PCI Hyper-V video\n");
-			kfree(info->apertures);
 			return -ENODEV;
 		}
 
@@ -1129,7 +1128,6 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 	} else {
 		pci_dev_put(pdev);
 	}
-	kfree(info->apertures);
 
 	return 0;
 
@@ -1141,7 +1139,6 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 err1:
 	if (!gen2vm)
 		pci_dev_put(pdev);
-	kfree(info->apertures);
 
 	return -ENOMEM;
 }
-- 
2.25.1