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* [PATCH 1/1] fbmem: Do not delete the mode that is still in use
@ 2021-07-12  8:55 Zhen Lei
  2021-07-12 14:37 ` Daniel Vetter
  0 siblings, 1 reply; 3+ messages in thread
From: Zhen Lei @ 2021-07-12  8:55 UTC (permalink / raw)
  To: Daniel Vetter, Sam Ravnborg, dri-devel, linux-fbdev, linux-kernel
  Cc: Zhen Lei, Maarten Lankhorst

The execution of fb_delete_videomode() is not based on the result of the
previous fbcon_mode_deleted(). As a result, the mode is directly deleted,
regardless of whether it is still in use, which may cause UAF.

==================================================================
BUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \
drivers/video/fbdev/core/modedb.c:924
Read of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962

CPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ...
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x137/0x1be lib/dump_stack.c:118
 print_address_description+0x6c/0x640 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report+0x13d/0x1e0 mm/kasan/report.c:562
 fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924
 fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746
 fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975
 do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 18960:
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
 kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0x108/0x140 mm/kasan/common.c:422
 slab_free_hook mm/slub.c:1541 [inline]
 slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574
 slab_free mm/slub.c:3139 [inline]
 kfree+0xca/0x3d0 mm/slub.c:4121
 fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104
 fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978
 do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 13ff178ccd6d ("fbcon: Call fbcon_mode_deleted/new_modelist directly")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 drivers/video/fbdev/core/fbmem.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 98f193078c05..1c855145711b 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -970,13 +970,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 		fb_var_to_videomode(&mode2, &info->var);
 		/* make sure we don't delete the videomode of current var */
 		ret = fb_mode_is_equal(&mode1, &mode2);
-
-		if (!ret)
-			fbcon_mode_deleted(info, &mode1);
-
-		if (!ret)
-			fb_delete_videomode(&mode1, &info->modelist);
-
+		if (!ret) {
+			ret = fbcon_mode_deleted(info, &mode1);
+			if (!ret)
+				fb_delete_videomode(&mode1, &info->modelist);
+		}
 
 		return ret ? -EINVAL : 0;
 	}
-- 
2.25.1



^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH 1/1] fbmem: Do not delete the mode that is still in use
  2021-07-12  8:55 [PATCH 1/1] fbmem: Do not delete the mode that is still in use Zhen Lei
@ 2021-07-12 14:37 ` Daniel Vetter
  2021-07-13 11:15   ` Daniel Vetter
  0 siblings, 1 reply; 3+ messages in thread
From: Daniel Vetter @ 2021-07-12 14:37 UTC (permalink / raw)
  To: Zhen Lei
  Cc: Daniel Vetter, Sam Ravnborg, dri-devel, linux-fbdev,
	linux-kernel, Maarten Lankhorst

On Mon, Jul 12, 2021 at 04:55:44PM +0800, Zhen Lei wrote:
> The execution of fb_delete_videomode() is not based on the result of the
> previous fbcon_mode_deleted(). As a result, the mode is directly deleted,
> regardless of whether it is still in use, which may cause UAF.
> 
> ==================================================================
> BUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \
> drivers/video/fbdev/core/modedb.c:924
> Read of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962
> 
> CPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ...
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x137/0x1be lib/dump_stack.c:118
>  print_address_description+0x6c/0x640 mm/kasan/report.c:385
>  __kasan_report mm/kasan/report.c:545 [inline]
>  kasan_report+0x13d/0x1e0 mm/kasan/report.c:562
>  fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924
>  fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746
>  fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975
>  do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
>  vfs_ioctl fs/ioctl.c:48 [inline]
>  __do_sys_ioctl fs/ioctl.c:753 [inline]
>  __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Freed by task 18960:
>  kasan_save_stack mm/kasan/common.c:48 [inline]
>  kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
>  kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
>  __kasan_slab_free+0x108/0x140 mm/kasan/common.c:422
>  slab_free_hook mm/slub.c:1541 [inline]
>  slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574
>  slab_free mm/slub.c:3139 [inline]
>  kfree+0xca/0x3d0 mm/slub.c:4121
>  fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104
>  fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978
>  do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
>  vfs_ioctl fs/ioctl.c:48 [inline]
>  __do_sys_ioctl fs/ioctl.c:753 [inline]
>  __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Fixes: 13ff178ccd6d ("fbcon: Call fbcon_mode_deleted/new_modelist directly")
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>

Nice catch, that indeed got lost.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: <stable@vger.kernel.org> # v5.3+

Needs to be applied to drm-misc-fixes, but the tree isn't ready yet.
-Daniel

> ---
>  drivers/video/fbdev/core/fbmem.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 98f193078c05..1c855145711b 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -970,13 +970,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
>  		fb_var_to_videomode(&mode2, &info->var);
>  		/* make sure we don't delete the videomode of current var */
>  		ret = fb_mode_is_equal(&mode1, &mode2);
> -
> -		if (!ret)
> -			fbcon_mode_deleted(info, &mode1);
> -
> -		if (!ret)
> -			fb_delete_videomode(&mode1, &info->modelist);
> -
> +		if (!ret) {
> +			ret = fbcon_mode_deleted(info, &mode1);
> +			if (!ret)
> +				fb_delete_videomode(&mode1, &info->modelist);
> +		}
>  
>  		return ret ? -EINVAL : 0;
>  	}
> -- 
> 2.25.1
> 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH 1/1] fbmem: Do not delete the mode that is still in use
  2021-07-12 14:37 ` Daniel Vetter
@ 2021-07-13 11:15   ` Daniel Vetter
  0 siblings, 0 replies; 3+ messages in thread
From: Daniel Vetter @ 2021-07-13 11:15 UTC (permalink / raw)
  To: Zhen Lei, Thomas Zimmermann
  Cc: Sam Ravnborg, dri-devel, linux-fbdev, linux-kernel, Maarten Lankhorst

On Mon, Jul 12, 2021 at 4:37 PM Daniel Vetter <daniel@ffwll.ch> wrote:
> On Mon, Jul 12, 2021 at 04:55:44PM +0800, Zhen Lei wrote:
> > The execution of fb_delete_videomode() is not based on the result of the
> > previous fbcon_mode_deleted(). As a result, the mode is directly deleted,
> > regardless of whether it is still in use, which may cause UAF.
> >
> > ==================================================================
> > BUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \
> > drivers/video/fbdev/core/modedb.c:924
> > Read of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962
> >
> > CPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ...
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x137/0x1be lib/dump_stack.c:118
> >  print_address_description+0x6c/0x640 mm/kasan/report.c:385
> >  __kasan_report mm/kasan/report.c:545 [inline]
> >  kasan_report+0x13d/0x1e0 mm/kasan/report.c:562
> >  fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924
> >  fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746
> >  fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975
> >  do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
> >  vfs_ioctl fs/ioctl.c:48 [inline]
> >  __do_sys_ioctl fs/ioctl.c:753 [inline]
> >  __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
> >  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >
> > Freed by task 18960:
> >  kasan_save_stack mm/kasan/common.c:48 [inline]
> >  kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
> >  kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
> >  __kasan_slab_free+0x108/0x140 mm/kasan/common.c:422
> >  slab_free_hook mm/slub.c:1541 [inline]
> >  slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574
> >  slab_free mm/slub.c:3139 [inline]
> >  kfree+0xca/0x3d0 mm/slub.c:4121
> >  fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104
> >  fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978
> >  do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
> >  vfs_ioctl fs/ioctl.c:48 [inline]
> >  __do_sys_ioctl fs/ioctl.c:753 [inline]
> >  __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
> >  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >
> > Fixes: 13ff178ccd6d ("fbcon: Call fbcon_mode_deleted/new_modelist directly")
> > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>
> Nice catch, that indeed got lost.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: <stable@vger.kernel.org> # v5.3+
>
> Needs to be applied to drm-misc-fixes, but the tree isn't ready yet.

Tree still isn't ready, adding Thomas.

Thomas, can you pls apply this when drm-misc-fixes is forwarded?

Thanks, Daniel

> -Daniel
>
> > ---
> >  drivers/video/fbdev/core/fbmem.c | 12 +++++-------
> >  1 file changed, 5 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> > index 98f193078c05..1c855145711b 100644
> > --- a/drivers/video/fbdev/core/fbmem.c
> > +++ b/drivers/video/fbdev/core/fbmem.c
> > @@ -970,13 +970,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
> >               fb_var_to_videomode(&mode2, &info->var);
> >               /* make sure we don't delete the videomode of current var */
> >               ret = fb_mode_is_equal(&mode1, &mode2);
> > -
> > -             if (!ret)
> > -                     fbcon_mode_deleted(info, &mode1);
> > -
> > -             if (!ret)
> > -                     fb_delete_videomode(&mode1, &info->modelist);
> > -
> > +             if (!ret) {
> > +                     ret = fbcon_mode_deleted(info, &mode1);
> > +                     if (!ret)
> > +                             fb_delete_videomode(&mode1, &info->modelist);
> > +             }
> >
> >               return ret ? -EINVAL : 0;
> >       }
> > --
> > 2.25.1
> >
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-07-13 11:15 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-12  8:55 [PATCH 1/1] fbmem: Do not delete the mode that is still in use Zhen Lei
2021-07-12 14:37 ` Daniel Vetter
2021-07-13 11:15   ` Daniel Vetter

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