Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
On Thu, Oct 29, 2020 at 01:13:01PM +0200, Jani Nikula wrote: > On Thu, 29 Oct 2020, Greg KH wrote: > > On Tue, Oct 27, 2020 at 10:12:49AM -0700, Saeed Mirzamohammadi wrote: > >> Hi Greg, > >> > >> Sorry for the confusion. I’m requesting stable maintainers to cherry-pick > >> this patch into stable 5.4 and 5.8. > >> commit cc07057c7c88fb8eff3b1991131ded0f0bcfa7e3 > >> Author: Saeed Mirzamohammadi > >> Date: Wed Oct 21 16:57:58 2020 -0700 > >> > >> video: fbdev: fix divide error in fbcon_switch > > > > I do not see that commit in Linus's tree, do you? > > It's in drm-misc-next, IIUC heading for Linus' tree in the next merge > window in 6-8 weeks. Which is to say this should probably have been > applied to drm-misc-fixes branch heading for v5.10-rcX, with a Cc: > stable tag, to begin with. Ok, nothing I can do with this now, please email sta...@vger.kernel.org when it hits Linus's tree and we can take it then. Saeed, please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly. thanks, greg k-h
Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
On Thu, 29 Oct 2020, Greg KH wrote: > On Tue, Oct 27, 2020 at 10:12:49AM -0700, Saeed Mirzamohammadi wrote: >> Hi Greg, >> >> Sorry for the confusion. I’m requesting stable maintainers to cherry-pick >> this patch into stable 5.4 and 5.8. >> commit cc07057c7c88fb8eff3b1991131ded0f0bcfa7e3 >> Author: Saeed Mirzamohammadi >> Date: Wed Oct 21 16:57:58 2020 -0700 >> >> video: fbdev: fix divide error in fbcon_switch > > I do not see that commit in Linus's tree, do you? It's in drm-misc-next, IIUC heading for Linus' tree in the next merge window in 6-8 weeks. Which is to say this should probably have been applied to drm-misc-fixes branch heading for v5.10-rcX, with a Cc: stable tag, to begin with. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center
Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
On Tue, Oct 27, 2020 at 10:12:49AM -0700, Saeed Mirzamohammadi wrote: > Hi Greg, > > Sorry for the confusion. I’m requesting stable maintainers to cherry-pick > this patch into stable 5.4 and 5.8. > commit cc07057c7c88fb8eff3b1991131ded0f0bcfa7e3 > Author: Saeed Mirzamohammadi > Date: Wed Oct 21 16:57:58 2020 -0700 > > video: fbdev: fix divide error in fbcon_switch I do not see that commit in Linus's tree, do you? confused, greg k-h
Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
On Mon, Oct 26, 2020 at 10:00:11AM -0700, Saeed Mirzamohammadi wrote: > Thanks, adding stable. Why? What are we supposed to do with this?
Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
Thanks, adding stable.
Saeed
> On Oct 22, 2020, at 12:34 AM, Thomas Zimmermann wrote:
>
> Hi
>
> On 22.10.20 01:57, saeed.mirzamohamm...@oracle.com wrote:
>> From: Saeed Mirzamohammadi
>>
>> This patch fixes the issue due to:
>>
>> [ 89.572883] divide_error: [#1] SMP KASAN PTI
>> [ 89.572897] CPU: 3 PID: 16083 Comm: repro Not tainted
>> 5.9.0-rc7.20200930.rc1.allarch-19-g3e32d0d.syzk #5
>> [ 89.572902] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>> 0.5.1 01/01/2011
>> [ 89.572934] RIP: 0010:cirrusfb_check_var+0x84/0x1260
>
> BTW, if you run qemu with cirrus, there's also a DRM driver named
> cirrus.ko. Might be a better choice than the old fbdev driver. If you
> just care about qemu, but not the actual graphics device, take a look at
>
>
> https://urldefense.com/v3/__https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/__;!!GqivPVa7Brio!LmgeM-pVBVH80uVELF1P1nBGAbAlhvnxKKE_ZrEc9d76AznvAAgP1FAp3_zNa2frKaIUZteK$
>
>
> Anyway, thanks for your patch.
>
> Best regards
> Thomas
>
>>
>> The error happens when the pixels value is calculated before performing the
>> sanity checks on bits_per_pixel.
>> A bits_per_pixel set to zero causes divide by zero error.
>>
>> This patch moves the calculation after the sanity check.
>>
>> Signed-off-by: Saeed Mirzamohammadi
>> Tested-by: Saeed Mirzamohammadi
>> ---
>> drivers/video/fbdev/cirrusfb.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/video/fbdev/cirrusfb.c b/drivers/video/fbdev/cirrusfb.c
>> index 15a9ee7cd734..a7749101b094 100644
>> --- a/drivers/video/fbdev/cirrusfb.c
>> +++ b/drivers/video/fbdev/cirrusfb.c
>> @@ -531,7 +531,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
>> *var,
>> {
>> int yres;
>> /* memory size in pixels */
>> -unsigned pixels = info->screen_size * 8 / var->bits_per_pixel;
>> +unsigned int pixels;
>> struct cirrusfb_info *cinfo = info->par;
>>
>> switch (var->bits_per_pixel) {
>> @@ -573,6 +573,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
>> *var,
>> return -EINVAL;
>> }
>>
>> +pixels = info->screen_size * 8 / var->bits_per_pixel;
>> if (var->xres_virtual < var->xres)
>> var->xres_virtual = var->xres;
>> /* use highest possible virtual resolution */
>>
>
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
Hi
On 22.10.20 01:57, saeed.mirzamohamm...@oracle.com wrote:
> From: Saeed Mirzamohammadi
>
> This patch fixes the issue due to:
>
> [ 89.572883] divide_error: [#1] SMP KASAN PTI
> [ 89.572897] CPU: 3 PID: 16083 Comm: repro Not tainted
> 5.9.0-rc7.20200930.rc1.allarch-19-g3e32d0d.syzk #5
> [ 89.572902] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 0.5.1 01/01/2011
> [ 89.572934] RIP: 0010:cirrusfb_check_var+0x84/0x1260
BTW, if you run qemu with cirrus, there's also a DRM driver named
cirrus.ko. Might be a better choice than the old fbdev driver. If you
just care about qemu, but not the actual graphics device, take a look at
https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/
Anyway, thanks for your patch.
Best regards
Thomas
>
> The error happens when the pixels value is calculated before performing the
> sanity checks on bits_per_pixel.
> A bits_per_pixel set to zero causes divide by zero error.
>
> This patch moves the calculation after the sanity check.
>
> Signed-off-by: Saeed Mirzamohammadi
> Tested-by: Saeed Mirzamohammadi
> ---
> drivers/video/fbdev/cirrusfb.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/cirrusfb.c b/drivers/video/fbdev/cirrusfb.c
> index 15a9ee7cd734..a7749101b094 100644
> --- a/drivers/video/fbdev/cirrusfb.c
> +++ b/drivers/video/fbdev/cirrusfb.c
> @@ -531,7 +531,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
> *var,
> {
> int yres;
> /* memory size in pixels */
> - unsigned pixels = info->screen_size * 8 / var->bits_per_pixel;
> + unsigned int pixels;
> struct cirrusfb_info *cinfo = info->par;
>
> switch (var->bits_per_pixel) {
> @@ -573,6 +573,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
> *var,
> return -EINVAL;
> }
>
> + pixels = info->screen_size * 8 / var->bits_per_pixel;
> if (var->xres_virtual < var->xres)
> var->xres_virtual = var->xres;
> /* use highest possible virtual resolution */
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
Hi
On 22.10.20 01:57, saeed.mirzamohamm...@oracle.com wrote:
> From: Saeed Mirzamohammadi
>
> This patch fixes the issue due to:
>
> [ 89.572883] divide_error: [#1] SMP KASAN PTI
> [ 89.572897] CPU: 3 PID: 16083 Comm: repro Not tainted
> 5.9.0-rc7.20200930.rc1.allarch-19-g3e32d0d.syzk #5
> [ 89.572902] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 0.5.1 01/01/2011
> [ 89.572934] RIP: 0010:cirrusfb_check_var+0x84/0x1260
>
> The error happens when the pixels value is calculated before performing the
> sanity checks on bits_per_pixel.
> A bits_per_pixel set to zero causes divide by zero error.
>
> This patch moves the calculation after the sanity check.
>
> Signed-off-by: Saeed Mirzamohammadi
> Tested-by: Saeed Mirzamohammadi
Looks good, thanks a lot. I'll add the patch to drm-misc-next
Reviewed-by: Thomas Zimemrmann
Best regards
Thomas
> ---
> drivers/video/fbdev/cirrusfb.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/cirrusfb.c b/drivers/video/fbdev/cirrusfb.c
> index 15a9ee7cd734..a7749101b094 100644
> --- a/drivers/video/fbdev/cirrusfb.c
> +++ b/drivers/video/fbdev/cirrusfb.c
> @@ -531,7 +531,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
> *var,
> {
> int yres;
> /* memory size in pixels */
> - unsigned pixels = info->screen_size * 8 / var->bits_per_pixel;
> + unsigned int pixels;
> struct cirrusfb_info *cinfo = info->par;
>
> switch (var->bits_per_pixel) {
> @@ -573,6 +573,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
> *var,
> return -EINVAL;
> }
>
> + pixels = info->screen_size * 8 / var->bits_per_pixel;
> if (var->xres_virtual < var->xres)
> var->xres_virtual = var->xres;
> /* use highest possible virtual resolution */
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
Re: [PATCH 1/1] video: fbdev: fix divide error in fbcon_switch
Attached the Syzkaller C reproducer.
repro.c
Description: Binary data
> On Oct 21, 2020, at 4:57 PM, saeed.mirzamohamm...@oracle.com wrote:
>
> From: Saeed Mirzamohammadi
>
> This patch fixes the issue due to:
>
> [ 89.572883] divide_error: [#1] SMP KASAN PTI
> [ 89.572897] CPU: 3 PID: 16083 Comm: repro Not tainted
> 5.9.0-rc7.20200930.rc1.allarch-19-g3e32d0d.syzk #5
> [ 89.572902] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 0.5.1 01/01/2011
> [ 89.572934] RIP: 0010:cirrusfb_check_var+0x84/0x1260
>
> The error happens when the pixels value is calculated before performing the
> sanity checks on bits_per_pixel.
> A bits_per_pixel set to zero causes divide by zero error.
>
> This patch moves the calculation after the sanity check.
>
> Signed-off-by: Saeed Mirzamohammadi
> Tested-by: Saeed Mirzamohammadi
> ---
> drivers/video/fbdev/cirrusfb.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/cirrusfb.c b/drivers/video/fbdev/cirrusfb.c
> index 15a9ee7cd734..a7749101b094 100644
> --- a/drivers/video/fbdev/cirrusfb.c
> +++ b/drivers/video/fbdev/cirrusfb.c
> @@ -531,7 +531,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
> *var,
> {
> int yres;
> /* memory size in pixels */
> - unsigned pixels = info->screen_size * 8 / var->bits_per_pixel;
> + unsigned int pixels;
> struct cirrusfb_info *cinfo = info->par;
>
> switch (var->bits_per_pixel) {
> @@ -573,6 +573,7 @@ static int cirrusfb_check_var(struct fb_var_screeninfo
> *var,
> return -EINVAL;
> }
>
> + pixels = info->screen_size * 8 / var->bits_per_pixel;
> if (var->xres_virtual < var->xres)
> var->xres_virtual = var->xres;
> /* use highest possible virtual resolution */
> --
> 2.27.0
>
