fbdev: imsttfb: Fix use after free bug in imsttfb_probe

commit c75f5a55061091030a13fef71b9995b89bc86213 upstream.

A use-after-free bug may occur if init_imstt invokes framebuffer_release
and free the info ptr. The caller, imsttfb_probe didn't notice that and
still keep the ptr as private data in pdev.

If we remove the driver which will call imsttfb_remove to make cleanup,
UAF happens.

Fix it by return error code if bad case happens in init_imstt.

Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/video/fbdev/imsttfb.c b/drivers/video/fbdev/imsttfb.c
index 6589d5f0a5a4062eba413841f85c389b31e62c7d..9b1a11bcd92135f82ef10cb60a0155f7eaffc615 100644 (file)
--- a/drivers/video/fbdev/imsttfb.c
+++ b/drivers/video/fbdev/imsttfb.c
@@ -1348,7 +1348,7 @@ static struct fb_ops imsttfb_ops = {
        .fb_ioctl       = imsttfb_ioctl,
 };
 
-static void init_imstt(struct fb_info *info)
+static int init_imstt(struct fb_info *info)
 {
        struct imstt_par *par = info->par;
        __u32 i, tmp, *ip, *end;
@@ -1420,7 +1420,7 @@ static void init_imstt(struct fb_info *info)
            || !(compute_imstt_regvals(par, info->var.xres, info->var.yres))) {
                printk("imsttfb: %ux%ux%u not supported\n", info->var.xres, info->var.yres, info->var.bits_per_pixel);
                framebuffer_release(info);
-               return;
+               return -ENODEV;
        }
 
        sprintf(info->fix.id, "IMS TT (%s)", par->ramdac == IBM ? "IBM" : "TVP");
@@ -1460,12 +1460,13 @@ static void init_imstt(struct fb_info *info)
        if (register_framebuffer(info) < 0) {
                fb_dealloc_cmap(&info->cmap);
                framebuffer_release(info);
-               return;
+               return -ENODEV;
        }
 
        tmp = (read_reg_le32(par->dc_regs, SSTATUS) & 0x0f00) >> 8;
        fb_info(info, "%s frame buffer; %uMB vram; chip version %u\n",
                info->fix.id, info->fix.smem_len >> 20, tmp);
+       return 0;
 }
 
 static int imsttfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
@@ -1474,7 +1475,8 @@ static int imsttfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
        struct imstt_par *par;
        struct fb_info *info;
        struct device_node *dp;
-       
+       int ret;
+
        dp = pci_device_to_OF_node(pdev);
        if(dp)
                printk(KERN_INFO "%s: OF name %s\n",__func__, dp->name);
@@ -1525,10 +1527,10 @@ static int imsttfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
        par->cmap_regs_phys = addr + 0x840000;
        par->cmap_regs = (__u8 *)ioremap(addr + 0x840000, 0x1000);
        info->pseudo_palette = par->palette;
-       init_imstt(info);
-
-       pci_set_drvdata(pdev, info);
-       return 0;
+       ret = init_imstt(info);
+       if (!ret)
+               pci_set_drvdata(pdev, info);
+       return ret;
 }
 
 static void imsttfb_remove(struct pci_dev *pdev)