[PATCH v2 1/4] staging: sm750fb: add bounds checking to option parsing in lynxfb_setup()

[PATCH v2 1/4] staging: sm750fb: add bounds checking to option parsing in lynxfb_setup()

[Artem Lytkin]

Replace strcat() with memcpy() and add explicit bounds checking on the
remaining buffer space before each copy. The original code lacked any
validation that the write position stays within the allocated buffer.

Signed-off-by: Artem Lytkin <iprintercanon@gmail.com>
---
 drivers/staging/sm750fb/sm750.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750.c b/drivers/staging/sm750fb/sm750.c
index fecd7457e..0eacb522d 100644
--- a/drivers/staging/sm750fb/sm750.c
+++ b/drivers/staging/sm750fb/sm750.c
@@ -1163,8 +1163,15 @@ static int __init lynxfb_setup(char *options)
 		} else if (!strncmp(opt, "dual", strlen("dual"))) {
 			g_dualview = 1;
 		} else {
-			strcat(tmp, opt);
-			tmp += strlen(opt);
+			size_t opt_len = strlen(opt);
+			size_t remaining = len - (tmp - g_settings);
+
+			if (opt_len + 1 >= remaining) {
+				pr_warn("option string too long\n");
+				break;
+			}
+			memcpy(tmp, opt, opt_len);
+			tmp += opt_len;
 			if (options)
 				*tmp++ = ':';
 			else
-- 
2.43.0

[PATCH v2 2/4] staging: sm750fb: use strcmp() for exact option matching

[Artem Lytkin]

Replace strncmp(opt, "...", strlen("...")) with strcmp() in option
parsing functions. Options from strsep() are complete null-terminated
tokens, so prefix matching via strncmp() could cause false positives
for options like "noaccelXYZ" matching "noaccel".

Signed-off-by: Artem Lytkin <iprintercanon@gmail.com>
---
 drivers/staging/sm750fb/sm750.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750.c b/drivers/staging/sm750fb/sm750.c
index 0eacb522d..73d78f893 100644
--- a/drivers/staging/sm750fb/sm750.c
+++ b/drivers/staging/sm750fb/sm750.c
@@ -937,21 +937,21 @@ static void sm750fb_setup(struct sm750_dev *sm750_dev, char *src)
 		dev_info(&sm750_dev->pdev->dev, "opt=%s\n", opt);
 		dev_info(&sm750_dev->pdev->dev, "src=%s\n", src);
 
-		if (!strncmp(opt, "swap", strlen("swap"))) {
+		if (!strcmp(opt, "swap")) {
 			swap = 1;
-		} else if (!strncmp(opt, "nocrt", strlen("nocrt"))) {
+		} else if (!strcmp(opt, "nocrt")) {
 			sm750_dev->nocrt = 1;
-		} else if (!strncmp(opt, "36bit", strlen("36bit"))) {
+		} else if (!strcmp(opt, "36bit")) {
 			sm750_dev->pnltype = sm750_doubleTFT;
-		} else if (!strncmp(opt, "18bit", strlen("18bit"))) {
+		} else if (!strcmp(opt, "18bit")) {
 			sm750_dev->pnltype = sm750_dualTFT;
-		} else if (!strncmp(opt, "24bit", strlen("24bit"))) {
+		} else if (!strcmp(opt, "24bit")) {
 			sm750_dev->pnltype = sm750_24TFT;
-		} else if (!strncmp(opt, "nohwc0", strlen("nohwc0"))) {
+		} else if (!strcmp(opt, "nohwc0")) {
 			g_hwcursor &= ~0x1;
-		} else if (!strncmp(opt, "nohwc1", strlen("nohwc1"))) {
+		} else if (!strcmp(opt, "nohwc1")) {
 			g_hwcursor &= ~0x2;
-		} else if (!strncmp(opt, "nohwc", strlen("nohwc"))) {
+		} else if (!strcmp(opt, "nohwc")) {
 			g_hwcursor = 0;
 		} else {
 			if (!g_fbmode[0]) {
@@ -1156,11 +1156,11 @@ static int __init lynxfb_setup(char *options)
 	 */
 	while ((opt = strsep(&options, ":")) != NULL) {
 		/* options that mean for any lynx chips are configured here */
-		if (!strncmp(opt, "noaccel", strlen("noaccel"))) {
+		if (!strcmp(opt, "noaccel")) {
 			g_noaccel = 1;
-		} else if (!strncmp(opt, "nomtrr", strlen("nomtrr"))) {
+		} else if (!strcmp(opt, "nomtrr")) {
 			g_nomtrr = 1;
-		} else if (!strncmp(opt, "dual", strlen("dual"))) {
+		} else if (!strcmp(opt, "dual")) {
 			g_dualview = 1;
 		} else {
 			size_t opt_len = strlen(opt);
-- 
2.43.0

[PATCH v2 3/4] staging: sm750fb: remove debug prints and convert logging in sm750.c

[Artem Lytkin]

Remove debug prints disguised as pr_info that dump internal variable
values, pointer addresses, and structure contents. Convert remaining
meaningful pr_err and pr_warn calls to dev_err and dev_warn where
device context is available.

Signed-off-by: Artem Lytkin <iprintercanon@gmail.com>
---
 drivers/staging/sm750fb/sm750.c | 85 ++++++++-------------------------
 1 file changed, 20 insertions(+), 65 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750.c b/drivers/staging/sm750fb/sm750.c
index 73d78f893..1feb97bee 100644
--- a/drivers/staging/sm750fb/sm750.c
+++ b/drivers/staging/sm750fb/sm750.c
@@ -375,7 +375,6 @@ static int lynxfb_ops_set_par(struct fb_info *info)
 	line_length = var->xres_virtual * var->bits_per_pixel / 8;
 	line_length = ALIGN(line_length, crtc->line_pad);
 	fix->line_length = line_length;
-	pr_info("fix->line_length = %d\n", fix->line_length);
 
 	/*
 	 * var->red,green,blue,transp are need to be set by driver
@@ -389,7 +388,8 @@ static int lynxfb_ops_set_par(struct fb_info *info)
 	var->accel_flags = 0;/*FB_ACCELF_TEXT;*/
 
 	if (ret) {
-		pr_err("bpp %d not supported\n", var->bits_per_pixel);
+		dev_err(info->device, "bpp %d not supported\n",
+			var->bits_per_pixel);
 		return ret;
 	}
 	ret = hw_sm750_crtc_set_mode(crtc, var, fix);
@@ -485,15 +485,11 @@ static int lynxfb_ops_check_var(struct fb_var_screeninfo *var,
 	par = info->par;
 	crtc = &par->crtc;
 
-	pr_debug("check var:%dx%d-%d\n",
-		 var->xres,
-		 var->yres,
-		 var->bits_per_pixel);
-
 	ret = lynxfb_set_color_offsets(info);
 
 	if (ret) {
-		pr_err("bpp %d not supported\n", var->bits_per_pixel);
+		dev_err(info->device, "bpp %d not supported\n",
+			var->bits_per_pixel);
 		return ret;
 	}
 
@@ -508,7 +504,7 @@ static int lynxfb_ops_check_var(struct fb_var_screeninfo *var,
 	request = ALIGN(request, crtc->line_pad);
 	request = request * var->yres_virtual;
 	if (crtc->vidmem_size < request) {
-		pr_err("not enough video memory for mode\n");
+		dev_err(info->device, "not enough video memory for mode\n");
 		return -ENOMEM;
 	}
 
@@ -533,7 +529,7 @@ static int lynxfb_ops_setcolreg(unsigned int regno,
 	ret = 0;
 
 	if (regno > 256) {
-		pr_err("regno = %d\n", regno);
+		dev_err(info->device, "regno = %d\n", regno);
 		return -EINVAL;
 	}
 
@@ -580,7 +576,6 @@ static int lynxfb_ops_blank(int blank, struct fb_info *info)
 	struct lynxfb_par *par;
 	struct lynxfb_output *output;
 
-	pr_debug("blank = %d.\n", blank);
 	par = info->par;
 	output = &par->output;
 	sm750_dev = par->dev;
@@ -625,7 +620,6 @@ static int sm750fb_set_drv(struct lynxfb_par *par)
 		crtc->channel = sm750_primary;
 		crtc->o_screen = 0;
 		crtc->v_screen = sm750_dev->pvMem;
-		pr_info("use simul primary mode\n");
 		break;
 	case sm750_simul_sec:
 		output->paths = sm750_pnc;
@@ -767,7 +761,6 @@ static int lynxfb_set_fbinfo(struct fb_info *info, int index)
 	crtc->cursor.mmio = sm750_dev->pvReg +
 		0x800f0 + (int)crtc->channel * 0x140;
 
-	pr_info("crtc->cursor.mmio = %p\n", crtc->cursor.mmio);
 	crtc->cursor.max_h = 64;
 	crtc->cursor.max_w = 64;
 	crtc->cursor.size = crtc->cursor.max_h * crtc->cursor.max_w * 2 / 8;
@@ -802,46 +795,26 @@ static int lynxfb_set_fbinfo(struct fb_info *info, int index)
 				   pdb[i], cdb[i], NULL, 8);
 
 		if (ret == 1) {
-			pr_info("success! use specified mode:%s in %s\n",
-				g_fbmode[index],
-				mdb_desc[i]);
+			dev_info(info->device,
+				 "use specified mode:%s in %s\n",
+				 g_fbmode[index],
+				 mdb_desc[i]);
 			break;
 		} else if (ret == 2) {
-			pr_warn("use specified mode:%s in %s,with an ignored refresh rate\n",
-				g_fbmode[index],
-				mdb_desc[i]);
+			dev_warn(info->device,
+				 "use specified mode:%s in %s, with an ignored refresh rate\n",
+				 g_fbmode[index],
+				 mdb_desc[i]);
 			break;
-		} else if (ret == 3) {
-			pr_warn("wanna use default mode\n");
-			/*break;*/
-		} else if (ret == 4) {
-			pr_warn("fall back to any valid mode\n");
+		} else if (ret == 3 || ret == 4) {
+			continue;
 		} else {
-			pr_warn("ret = %d,fb_find_mode failed,with %s\n",
-				ret,
-				mdb_desc[i]);
+			dev_warn(info->device,
+				 "fb_find_mode failed with %s (ret=%d)\n",
+				 mdb_desc[i], ret);
 		}
 	}
 
-	/* some member of info->var had been set by fb_find_mode */
-
-	pr_info("Member of info->var is :\n"
-		"xres=%d\n"
-		"yres=%d\n"
-		"xres_virtual=%d\n"
-		"yres_virtual=%d\n"
-		"xoffset=%d\n"
-		"yoffset=%d\n"
-		"bits_per_pixel=%d\n"
-		" ...\n",
-		var->xres,
-		var->yres,
-		var->xres_virtual,
-		var->yres_virtual,
-		var->xoffset,
-		var->yoffset,
-		var->bits_per_pixel);
-
 	/* set par */
 	par->info = info;
 
@@ -851,7 +824,6 @@ static int lynxfb_set_fbinfo(struct fb_info *info, int index)
 
 	info->pseudo_palette = &par->pseudo_palette[0];
 	info->screen_base = crtc->v_screen;
-	pr_debug("screen_base vaddr = %p\n", info->screen_base);
 	info->screen_size = line_length * var->yres_virtual;
 
 	/* set info->fix */
@@ -865,7 +837,6 @@ static int lynxfb_set_fbinfo(struct fb_info *info, int index)
 	strscpy(fix->id, fixId[index], sizeof(fix->id));
 
 	fix->smem_start = crtc->o_screen + sm750_dev->vidmem_start;
-	pr_info("fix->smem_start = %lx\n", fix->smem_start);
 	/*
 	 * according to mmap experiment from user space application,
 	 * fix->mmio_len should not larger than virtual size
@@ -874,13 +845,10 @@ static int lynxfb_set_fbinfo(struct fb_info *info, int index)
 	 * data into the bound over virtual size
 	 */
 	fix->smem_len = crtc->vidmem_size;
-	pr_info("fix->smem_len = %x\n", fix->smem_len);
 	info->screen_size = fix->smem_len;
 	fix->line_length = line_length;
 	fix->mmio_start = sm750_dev->vidreg_start;
-	pr_info("fix->mmio_start = %lx\n", fix->mmio_start);
 	fix->mmio_len = sm750_dev->vidreg_size;
-	pr_info("fix->mmio_len = %x\n", fix->mmio_len);
 
 	lynxfb_set_visual_mode(info);
 
@@ -889,22 +857,12 @@ static int lynxfb_set_fbinfo(struct fb_info *info, int index)
 	var->accel_flags = 0;
 	var->vmode = FB_VMODE_NONINTERLACED;
 
-	pr_debug("#1 show info->cmap :\nstart=%d,len=%d,red=%p,green=%p,blue=%p,transp=%p\n",
-		 info->cmap.start, info->cmap.len,
-		 info->cmap.red, info->cmap.green, info->cmap.blue,
-		 info->cmap.transp);
-
 	ret = fb_alloc_cmap(&info->cmap, 256, 0);
 	if (ret < 0) {
-		pr_err("Could not allocate memory for cmap.\n");
+		dev_err(info->device, "Could not allocate memory for cmap.\n");
 		goto exit;
 	}
 
-	pr_debug("#2 show info->cmap :\nstart=%d,len=%d,red=%p,green=%p,blue=%p,transp=%p\n",
-		 info->cmap.start, info->cmap.len,
-		 info->cmap.red, info->cmap.green, info->cmap.blue,
-		 info->cmap.transp);
-
 exit:
 	lynxfb_ops_check_var(var, info);
 	return ret;
@@ -934,9 +892,6 @@ static void sm750fb_setup(struct sm750_dev *sm750_dev, char *src)
 	}
 
 	while ((opt = strsep(&src, ":")) != NULL && *opt != 0) {
-		dev_info(&sm750_dev->pdev->dev, "opt=%s\n", opt);
-		dev_info(&sm750_dev->pdev->dev, "src=%s\n", src);
-
 		if (!strcmp(opt, "swap")) {
 			swap = 1;
 		} else if (!strcmp(opt, "nocrt")) {
-- 
2.43.0

[PATCH v2 4/4] staging: sm750fb: remove debug prints and convert logging in sm750_hw.c

[Artem Lytkin]

Remove diagnostic pr_info prints that dump physical and virtual
memory addresses. Convert remaining pr_err calls to dev_err in
hw_sm750_map() where struct pci_dev *pdev is available.

Signed-off-by: Artem Lytkin <iprintercanon@gmail.com>
---
 drivers/staging/sm750fb/sm750_hw.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750_hw.c b/drivers/staging/sm750fb/sm750_hw.c
index ce46f240c..420ebe057 100644
--- a/drivers/staging/sm750fb/sm750_hw.c
+++ b/drivers/staging/sm750fb/sm750_hw.c
@@ -34,8 +34,6 @@ int hw_sm750_map(struct sm750_dev *sm750_dev, struct pci_dev *pdev)
 	sm750_dev->vidreg_start = pci_resource_start(pdev, 1);
 	sm750_dev->vidreg_size = SZ_2M;
 
-	pr_info("mmio phyAddr = %lx\n", sm750_dev->vidreg_start);
-
 	/*
 	 * reserve the vidreg space of smi adaptor
 	 * if you do this, you need to add release region code
@@ -44,7 +42,7 @@ int hw_sm750_map(struct sm750_dev *sm750_dev, struct pci_dev *pdev)
 	 */
 	ret = pci_request_region(pdev, 1, "sm750fb");
 	if (ret) {
-		pr_err("Can not request PCI regions.\n");
+		dev_err(&pdev->dev, "Can not request PCI regions.\n");
 		goto exit;
 	}
 
@@ -52,12 +50,10 @@ int hw_sm750_map(struct sm750_dev *sm750_dev, struct pci_dev *pdev)
 	sm750_dev->pvReg =
 		ioremap(sm750_dev->vidreg_start, sm750_dev->vidreg_size);
 	if (!sm750_dev->pvReg) {
-		pr_err("mmio failed\n");
+		dev_err(&pdev->dev, "mmio failed\n");
 		ret = -EFAULT;
 		goto exit;
 	}
-	pr_info("mmio virtual addr = %p\n", sm750_dev->pvReg);
-
 	sm750_dev->accel.dpr_base = sm750_dev->pvReg + DE_BASE_ADDR_TYPE1;
 	sm750_dev->accel.dp_port_base = sm750_dev->pvReg + DE_PORT_ADDR_TYPE1;
 
@@ -72,19 +68,16 @@ int hw_sm750_map(struct sm750_dev *sm750_dev, struct pci_dev *pdev)
 	 * @ddk750_get_vm_size function can be safe.
 	 */
 	sm750_dev->vidmem_size = ddk750_get_vm_size();
-	pr_info("video memory phyAddr = %lx, size = %u bytes\n",
-		sm750_dev->vidmem_start, sm750_dev->vidmem_size);
 
 	/* reserve the vidmem space of smi adaptor */
 	sm750_dev->pvMem =
 		ioremap_wc(sm750_dev->vidmem_start, sm750_dev->vidmem_size);
 	if (!sm750_dev->pvMem) {
 		iounmap(sm750_dev->pvReg);
-		pr_err("Map video memory failed\n");
+		dev_err(&pdev->dev, "Map video memory failed\n");
 		ret = -EFAULT;
 		goto exit;
 	}
-	pr_info("video memory vaddr = %p\n", sm750_dev->pvMem);
 exit:
 	return ret;
 }
@@ -163,11 +156,11 @@ int hw_sm750_inithw(struct sm750_dev *sm750_dev, struct pci_dev *pdev)
 			 * The following register values for CH7301 are from
 			 * Chrontel app note and our experiment.
 			 */
-			pr_info("yes,CH7301 DVI chip found\n");
+			dev_info(&pdev->dev, "CH7301 DVI chip found\n");
 			sm750_sw_i2c_write_reg(0xec, 0x1d, 0x16);
 			sm750_sw_i2c_write_reg(0xec, 0x21, 0x9);
 			sm750_sw_i2c_write_reg(0xec, 0x49, 0xC0);
-			pr_info("okay,CH7301 DVI chip setup done\n");
+			dev_info(&pdev->dev, "CH7301 DVI chip setup done\n");
 		}
 	}
 
-- 
2.43.0

Re: [PATCH v2 1/4] staging: sm750fb: add bounds checking to option parsing in lynxfb_setup()

[Dan Carpenter]

On Wed, Feb 04, 2026 at 10:15:33AM +0000, Artem Lytkin wrote:
> Replace strcat() with memcpy() and add explicit bounds checking on the
> remaining buffer space before each copy. The original code lacked any
> validation that the write position stays within the allocated buffer.
> 

This implies that there is a buffer overflow.  It's important to review
this sort of thing and add a Fixes tag if the buffer overflow is real.

In this case the code works ok as-is.  My main problem with the
original code is what you explained in the v1 commit, the strcat() was
just doing a memcpy().  It wasn't concatenating two strings.

Just resend the v1 patch with the following commit message:

  As part of kernel hardening, I am auditing calls to strcat().  This
  code works but it is a bit ugly.

  This function takes a string "options" and allocates "g_settings"
  which is large enough to hold a copy of "options".  It copies all the
  options from "options" to "g_settings" except "noaccel", "nomtrr" and
  "dual".  The new buffer is large enough to fit all the options so
  there is no buffer overflow in using strcat() here.

  However, using strcat() is misleading because "tmp" always points
  to the next unused character in the "g_settings" buffer and it's
  always the NUL character.  Use memcpy() instead to make the code
  easier to read.  This also removes an instance of strcat() which
  is a #NiceBonus.

regards,
dan carpenter

Re: [PATCH v2 2/4] staging: sm750fb: use strcmp() for exact option matching

[Dan Carpenter]

On Wed, Feb 04, 2026 at 10:15:34AM +0000, Artem Lytkin wrote:
> Replace strncmp(opt, "...", strlen("...")) with strcmp() in option
> parsing functions. Options from strsep() are complete null-terminated
> tokens, so prefix matching via strncmp() could cause false positives
> for options like "noaccelXYZ" matching "noaccel".
> 
> Signed-off-by: Artem Lytkin <iprintercanon@gmail.com>
> ---

You've changed how the code works and this is a bugfix.  It should have
a Fixes tag.

regards,
dan carpenter

Re: [PATCH v2 3/4] staging: sm750fb: remove debug prints and convert logging in sm750.c

[Dan Carpenter]

On Wed, Feb 04, 2026 at 10:15:35AM +0000, Artem Lytkin wrote:
> Remove debug prints disguised as pr_info that dump internal variable
> values, pointer addresses, and structure contents. Convert remaining
> meaningful pr_err and pr_warn calls to dev_err and dev_warn where
> device context is available.

I feel like you should delete things as a separate step.  It makes it
slightly easier to think about.

It's really a no brainer to delete all the pr_info() stuff.  I don't
really have a problem deleting the debug code as well, but that's a
slightly more involved question because it doesn't really hurt anyone.
I guess no one will complain.  Greg tends to be a fan of deleting stuff
as well.

regards,
dan carpenter

Re: [PATCH v2 4/4] staging: sm750fb: remove debug prints and convert logging in sm750_hw.c

[Dan Carpenter]

On Wed, Feb 04, 2026 at 10:15:36AM +0000, Artem Lytkin wrote:
> @@ -163,11 +156,11 @@ int hw_sm750_inithw(struct sm750_dev *sm750_dev, struct pci_dev *pdev)
>  			 * The following register values for CH7301 are from
>  			 * Chrontel app note and our experiment.
>  			 */
> -			pr_info("yes,CH7301 DVI chip found\n");
> +			dev_info(&pdev->dev, "CH7301 DVI chip found\n");
>  			sm750_sw_i2c_write_reg(0xec, 0x1d, 0x16);
>  			sm750_sw_i2c_write_reg(0xec, 0x21, 0x9);
>  			sm750_sw_i2c_write_reg(0xec, 0x49, 0xC0);
> -			pr_info("okay,CH7301 DVI chip setup done\n");
> +			dev_info(&pdev->dev, "CH7301 DVI chip setup done\n");

Delete at least one of these.  Pretty sure that Greg will want you to
delete both actually.

regards,
dan carpenter