Re: [PATCH 1/4] fbdev: imsttfb: Fix error handling in init_imstt()

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On 5/23/23 19:38, Markus Elfring wrote:
From: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 23 May 2023 14:32:39 +0200

The return value was overlooked from a call of
the function “fb_alloc_cmap”.

* Thus use a corresponding error check.

* Add two jump targets so that a bit of exception handling
   can be better reused at the end of this function.


Reported-by: Helge Deller <deller@xxxxxx>
Link: https://lore.kernel.org/dri-devel/069f2f78-01f3-9476-d860-2b695c122649@xxxxxx/
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Fixes: c75f5a550610 ("fbdev: imsttfb: Fix use after free bug in imsttfb_probe")
Signed-off-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
---
  drivers/video/fbdev/imsttfb.c | 18 +++++++++++++-----
  1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/video/fbdev/imsttfb.c b/drivers/video/fbdev/imsttfb.c
index 975dd682fae4..d3532def4707 100644
--- a/drivers/video/fbdev/imsttfb.c
+++ b/drivers/video/fbdev/imsttfb.c
@@ -1351,6 +1351,7 @@ static int init_imstt(struct fb_info *info)
  {
  	struct imstt_par *par = info->par;
  	__u32 i, tmp, *ip, *end;
+	int ret;

  	tmp = read_reg_le32(par->dc_regs, PRC);
  	if (par->ramdac == IBM)
@@ -1419,8 +1420,7 @@ static int init_imstt(struct fb_info *info)
  	if ((info->var.xres * info->var.yres) * (info->var.bits_per_pixel >> 3) > info->fix.smem_len
  	    || !(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 -ENODEV;
+		goto e_nodev;
  	}

  	sprintf(info->fix.id, "IMS TT (%s)", par->ramdac == IBM ? "IBM" : "TVP");
@@ -1452,17 +1452,25 @@ static int init_imstt(struct fb_info *info)
  	              FBINFO_HWACCEL_FILLRECT |
  	              FBINFO_HWACCEL_YPAN;

-	fb_alloc_cmap(&info->cmap, 0, 0);
+	ret = fb_alloc_cmap(&info->cmap, 0, 0);
+	if (ret)
+		goto release_framebuffer;

  	if (register_framebuffer(info) < 0) {
-		framebuffer_release(info);
-		return -ENODEV;
+		fb_dealloc_cmap(&info->cmap);
+		goto e_nodev;
  	}

  	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;
+
+e_nodev:
+	ret = -ENODEV;

I think the return value isn't checked at all, so you could
simply return below "-ENODEV" for all cases (instead of "return ret").
Then you don't need the e_nodev label and can simplify the flow.

Helge


+release_framebuffer:
+	framebuffer_release(info);
+	return ret;
  }

  static int imsttfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
--
2.40.1






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