[PATCH stable 4.14 v2 0/3] add fix patches for CVE-2021-33655

[PATCH stable 4.14 v2 0/3] add fix patches for CVE-2021-33655

[Chen Jun]

v2: add patch d48de54a9dab ("printk: Export is_console_locked") to fix a build error
caused by v1 if CONFIG_FB = m.
	ERROR: "is_console_locked" [drivers/video/fbdev/core/fb.ko] undefined!

v1: https://lore.kernel.org/stable/20220729031140.21806-1-chenjun102@huawei.com/

Hans de Goede (1):
  printk: Export is_console_locked

Helge Deller (2):
  fbcon: Prevent that screen size is smaller than font size
  fbmem: Check virtual screen sizes in fb_set_var()

 drivers/video/fbdev/core/fbcon.c | 28 ++++++++++++++++++++++++++++
 drivers/video/fbdev/core/fbmem.c | 20 +++++++++++++++++---
 include/linux/fbcon.h            |  4 ++++
 kernel/printk/printk.c           |  1 +
 4 files changed, 50 insertions(+), 3 deletions(-)

-- 
2.17.1

[PATCH stable 4.14 v2 1/3] printk: Export is_console_locked

[Chen Jun]

From: Hans de Goede <hdegoede@redhat.com>

commit d48de54a9dab5370edd2e991f78cc7996cf5483e upstream

This is a preparation patch for adding a number of WARN_CONSOLE_UNLOCKED()
calls to the fbcon code, which may be built as a module (event though
usually it is not).

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
---
 kernel/printk/printk.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 11173d0b51bc..ad4772869d48 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2259,6 +2259,7 @@ int is_console_locked(void)
 {
 	return console_locked;
 }
+EXPORT_SYMBOL(is_console_locked);
 
 /*
  * Check if we have any console that is capable of printing while cpu is
-- 
2.17.1

[PATCH stable 4.14 v2 2/3] fbcon: Prevent that screen size is smaller than font size

[Chen Jun]

From: Helge Deller <deller@gmx.de>

commit e64242caef18b4a5840b0e7a9bff37abd4f4f933 upstream

We need to prevent that users configure a screen size which is smaller than the
currently selected font size. Otherwise rendering chars on the screen will
access memory outside the graphics memory region.

This patch adds a new function fbcon_modechange_possible() which
implements this check and which later may be extended with other checks
if necessary.  The new function is called from the FBIOPUT_VSCREENINFO
ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
for a too small screen size.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/all/20220706150253.2186-1-deller@gmx.de/
[sudip: adjust context]
Signed-off-by: Chen Jun <chenjun102@huawei.com>
---
 drivers/video/fbdev/core/fbcon.c | 28 ++++++++++++++++++++++++++++
 drivers/video/fbdev/core/fbmem.c | 10 +++++++---
 include/linux/fbcon.h            |  4 ++++
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index a97e94b1c84f..b84264e98929 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2706,6 +2706,34 @@ static void fbcon_set_all_vcs(struct fb_info *info)
 		fbcon_modechanged(info);
 }
 
+/* let fbcon check if it supports a new screen resolution */
+int fbcon_modechange_possible(struct fb_info *info, struct fb_var_screeninfo *var)
+{
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct vc_data *vc;
+	unsigned int i;
+
+	WARN_CONSOLE_UNLOCKED();
+
+	if (!ops)
+		return 0;
+
+	/* prevent setting a screen size which is smaller than font size */
+	for (i = first_fb_vc; i <= last_fb_vc; i++) {
+		vc = vc_cons[i].d;
+		if (!vc || vc->vc_mode != KD_TEXT ||
+			   registered_fb[con2fb_map[i]] != info)
+			continue;
+
+		if (vc->vc_font.width  > FBCON_SWAP(var->rotate, var->xres, var->yres) ||
+		    vc->vc_font.height > FBCON_SWAP(var->rotate, var->yres, var->xres))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fbcon_modechange_possible);
+
 static int fbcon_mode_deleted(struct fb_info *info,
 			      struct fb_videomode *mode)
 {
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 9087d467cc46..264e8ca5efa7 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1134,9 +1134,13 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
 			console_unlock();
 			return -ENODEV;
 		}
-		info->flags |= FBINFO_MISC_USEREVENT;
-		ret = fb_set_var(info, &var);
-		info->flags &= ~FBINFO_MISC_USEREVENT;
+		ret = fbcon_modechange_possible(info, &var);
+		if (!ret) {
+			info->flags |= FBINFO_MISC_USEREVENT;
+			ret = fb_set_var(info, &var);
+			info->flags &= ~FBINFO_MISC_USEREVENT;
+		}
+		lock_fb_info(info);
 		unlock_fb_info(info);
 		console_unlock();
 		if (!ret && copy_to_user(argp, &var, sizeof(var)))
diff --git a/include/linux/fbcon.h b/include/linux/fbcon.h
index f68a7db14165..39939d55c834 100644
--- a/include/linux/fbcon.h
+++ b/include/linux/fbcon.h
@@ -4,9 +4,13 @@
 #ifdef CONFIG_FRAMEBUFFER_CONSOLE
 void __init fb_console_init(void);
 void __exit fb_console_exit(void);
+int  fbcon_modechange_possible(struct fb_info *info,
+			       struct fb_var_screeninfo *var);
 #else
 static inline void fb_console_init(void) {}
 static inline void fb_console_exit(void) {}
+static inline int  fbcon_modechange_possible(struct fb_info *info,
+				struct fb_var_screeninfo *var) { return 0; }
 #endif
 
 #endif /* _LINUX_FBCON_H */
-- 
2.17.1

Re: [PATCH stable 4.14 v2 2/3] fbcon: Prevent that screen size is smaller than font size

[Greg KH]

On Thu, Aug 04, 2022 at 11:15:38AM +0000, Chen Jun wrote:
> From: Helge Deller <deller@gmx.de>
> 
> commit e64242caef18b4a5840b0e7a9bff37abd4f4f933 upstream
> 
> We need to prevent that users configure a screen size which is smaller than the
> currently selected font size. Otherwise rendering chars on the screen will
> access memory outside the graphics memory region.
> 
> This patch adds a new function fbcon_modechange_possible() which
> implements this check and which later may be extended with other checks
> if necessary.  The new function is called from the FBIOPUT_VSCREENINFO
> ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
> for a too small screen size.
> 
> Signed-off-by: Helge Deller <deller@gmx.de>
> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Link: https://lore.kernel.org/all/20220706150253.2186-1-deller@gmx.de/
> [sudip: adjust context]

Who is "sudip" here?

And the Link: line wasn't in the original commit, where did that come
from?

thanks,

greg k-h

Re: [PATCH stable 4.14 v2 2/3] fbcon: Prevent that screen size is smaller than font size

[chenjun (AM)]

在 2022/8/4 19:50, Greg KH 写道:
> On Thu, Aug 04, 2022 at 11:15:38AM +0000, Chen Jun wrote:
>> From: Helge Deller <deller@gmx.de>
>>
>> commit e64242caef18b4a5840b0e7a9bff37abd4f4f933 upstream
>>
>> We need to prevent that users configure a screen size which is smaller than the
>> currently selected font size. Otherwise rendering chars on the screen will
>> access memory outside the graphics memory region.
>>
>> This patch adds a new function fbcon_modechange_possible() which
>> implements this check and which later may be extended with other checks
>> if necessary.  The new function is called from the FBIOPUT_VSCREENINFO
>> ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
>> for a too small screen size.
>>
>> Signed-off-by: Helge Deller <deller@gmx.de>
>> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
>> Link: https://lore.kernel.org/all/20220706150253.2186-1-deller@gmx.de/
>> [sudip: adjust context]
> 
> Who is "sudip" here?

Em..I misunderstood the meaning "sudip". I just mean I made some 
contextual adjustments.

> And the Link: line wasn't in the original commit, where did that come
> from?
> 

The mainline commit appears to be from this link. Should I remove the link?

> thanks,
> 
> greg k-h
> 

-- 
Regards
Chen Jun

Re: [PATCH stable 4.14 v2 2/3] fbcon: Prevent that screen size is smaller than font size

[Greg KH]

On Thu, Aug 04, 2022 at 12:01:57PM +0000, chenjun (AM) wrote:
> 在 2022/8/4 19:50, Greg KH 写道:
> > On Thu, Aug 04, 2022 at 11:15:38AM +0000, Chen Jun wrote:
> >> From: Helge Deller <deller@gmx.de>
> >>
> >> commit e64242caef18b4a5840b0e7a9bff37abd4f4f933 upstream
> >>
> >> We need to prevent that users configure a screen size which is smaller than the
> >> currently selected font size. Otherwise rendering chars on the screen will
> >> access memory outside the graphics memory region.
> >>
> >> This patch adds a new function fbcon_modechange_possible() which
> >> implements this check and which later may be extended with other checks
> >> if necessary.  The new function is called from the FBIOPUT_VSCREENINFO
> >> ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
> >> for a too small screen size.
> >>
> >> Signed-off-by: Helge Deller <deller@gmx.de>
> >> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> >> Link: https://lore.kernel.org/all/20220706150253.2186-1-deller@gmx.de/
> >> [sudip: adjust context]
> > 
> > Who is "sudip" here?
> 
> Em..I misunderstood the meaning "sudip". I just mean I made some 
> contextual adjustments.

Then please use your name here when you resend them.

> > And the Link: line wasn't in the original commit, where did that come
> > from?
> > 
> 
> The mainline commit appears to be from this link. Should I remove the link?

It is odd to see fields that are not in the upstream commit be added
without any explaination (i.e. it's not an obvious signed-off-by
addition), which is why I asked where it came from.

We can add these, but for some reason the upstream maintainer did not
when applying it to their trees, so it's up to you if you want to dig up
the information like this or not, it's not a trivial task at times.

thanks,

greg k-h

Re: [PATCH stable 4.14 v2 2/3] fbcon: Prevent that screen size is smaller than font size

[chenjun (AM)]

在 2022/8/4 20:09, Greg KH 写道:
> On Thu, Aug 04, 2022 at 12:01:57PM +0000, chenjun (AM) wrote:
>> 在 2022/8/4 19:50, Greg KH 写道:
>>> On Thu, Aug 04, 2022 at 11:15:38AM +0000, Chen Jun wrote:
>>>> From: Helge Deller <deller@gmx.de>
>>>>
>>>> commit e64242caef18b4a5840b0e7a9bff37abd4f4f933 upstream
>>>>
>>>> We need to prevent that users configure a screen size which is smaller than the
>>>> currently selected font size. Otherwise rendering chars on the screen will
>>>> access memory outside the graphics memory region.
>>>>
>>>> This patch adds a new function fbcon_modechange_possible() which
>>>> implements this check and which later may be extended with other checks
>>>> if necessary.  The new function is called from the FBIOPUT_VSCREENINFO
>>>> ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
>>>> for a too small screen size.
>>>>
>>>> Signed-off-by: Helge Deller <deller@gmx.de>
>>>> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
>>>> Link: https://lore.kernel.org/all/20220706150253.2186-1-deller@gmx.de/
>>>> [sudip: adjust context]
>>>
>>> Who is "sudip" here?
>>
>> Em..I misunderstood the meaning "sudip". I just mean I made some
>> contextual adjustments.
> 
> Then please use your name here when you resend them >
>>> And the Link: line wasn't in the original commit, where did that come
>>> from?
>>>
>>
>> The mainline commit appears to be from this link. Should I remove the link?
> 
> It is odd to see fields that are not in the upstream commit be added
> without any explaination (i.e. it's not an obvious signed-off-by
> addition), which is why I asked where it came from.
> 
> We can add these, but for some reason the upstream maintainer did not
> when applying it to their trees, so it's up to you if you want to dig up
> the information like this or not, it's not a trivial task at times.
> 
> thanks,
> 
> greg k-h
> 

Very thanks for your opinion.
I will sent v3.

-- 
Regards
Chen Jun

[PATCH stable 4.14 v2 3/3] fbmem: Check virtual screen sizes in fb_set_var()

[Chen Jun]

From: Helge Deller <deller@gmx.de>

commit 6c11df58fd1ac0aefcb3b227f72769272b939e56 upstream

Verify that the fbdev or drm driver correctly adjusted the virtual
screen sizes. On failure report the failing driver and reject the screen
size change.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/all/20220706150253.2186-1-deller@gmx.de/
[sudip: adjust context]
Signed-off-by: Chen Jun <chenjun102@huawei.com>
---
 drivers/video/fbdev/core/fbmem.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 264e8ca5efa7..1238cc9f42c0 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1019,6 +1019,16 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 		if (ret)
 			goto done;
 
+		/* verify that virtual resolution >= physical resolution */
+		if (var->xres_virtual < var->xres ||
+		    var->yres_virtual < var->yres) {
+			pr_warn("WARNING: fbcon: Driver '%s' missed to adjust virtual screen size (%ux%u vs. %ux%u)\n",
+				info->fix.id,
+				var->xres_virtual, var->yres_virtual,
+				var->xres, var->yres);
+			return -EINVAL;
+		}
+
 		if ((var->activate & FB_ACTIVATE_MASK) == FB_ACTIVATE_NOW) {
 			struct fb_var_screeninfo old_var;
 			struct fb_videomode mode;
-- 
2.17.1