video: hyperv_fb: Fix a double free in hvfb_probe

BugLink: https://bugs.launchpad.net/bugs/1923069
[ 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@mail.ustc.edu.cn>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20210324103724.4189-1-lyl2019@mail.ustc.edu.cn
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
index c8b0ae676809ba041e954ad876ec71e76da8b0ba..4dc9077dd2ac04d07401e210b13fcb052b0f6ab1 100644 (file)
--- 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;
 }