linux-kernel - [PATCH 5.10 103/126] video: hyperv_fb: Fix a double free in hvfb

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Date:   Mon,  5 Apr 2021 10:54:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lv Yunlong <lyl2019@...l.ustc.edu.cn>,
        Michael Kelley <mikelley@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 103/126] video: hyperv_fb: Fix a double free in hvfb_probe

From: Lv Yunlong <lyl2019@...l.ustc.edu.cn>

[ Upstream commit 37df9f3fedb6aeaff5564145e8162aab912c9284 ]

Function hvfb_probe() calls hvfb_getmem(), expecting upon return that
info->apertures is either NULL or points to memory that should be freed
by framebuffer_release().  But hvfb_getmem() is freeing the memory and
leaving the pointer non-NULL, resulting in a double free if an error
occurs or later if hvfb_remove() is called.

Fix this by removing all kfree(info->apertures) calls in hvfb_getmem().
This will allow framebuffer_release() to free the memory, which follows
the pattern of other fbdev drivers.

Fixes: 3a6fb6c4255c ("video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.")
Signed-off-by: Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
Link: https://lore.kernel.org/r/20210324103724.4189-1-lyl2019@mail.ustc.edu.cn
Signed-off-by: Wei Liu <wei.liu@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 @@ getmem_done:
 	} else {
 		pci_dev_put(pdev);
 	}
-	kfree(info->apertures);
 
 	return 0;
 
@@ -1141,7 +1139,6 @@ err2:
 err1:
 	if (!gen2vm)
 		pci_dev_put(pdev);
-	kfree(info->apertures);
 
 	return -ENOMEM;
 }
-- 
2.30.2