[v4] vgacon: Fix a UAF in vgacon_invert_region

[v4] vgacon: Fix a UAF in vgacon_invert_region

[Zhang Xiaoxu]

When syzkaller tests, there is a UAF:
  BUG: KASan: use after free in vgacon_invert_region+0x9d/0x110 at addr
    ffff880000100000
  Read of size 2 by task syz-executor.1/16489
  page:ffffea0000004000 count:0 mapcount:-127 mapping:          (null)
  index:0x0
  page flags: 0xfffff00000000()
  page dumped because: kasan: bad access detected
  CPU: 1 PID: 16489 Comm: syz-executor.1 Not tainted
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
  rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
  Call Trace:
    [<ffffffffb119f309>] dump_stack+0x1e/0x20
    [<ffffffffb04af957>] kasan_report+0x577/0x950
    [<ffffffffb04ae652>] __asan_load2+0x62/0x80
    [<ffffffffb090f26d>] vgacon_invert_region+0x9d/0x110
    [<ffffffffb0a39d95>] invert_screen+0xe5/0x470
    [<ffffffffb0a21dcb>] set_selection+0x44b/0x12f0
    [<ffffffffb0a3bfae>] tioclinux+0xee/0x490
    [<ffffffffb0a1d114>] vt_ioctl+0xff4/0x2670
    [<ffffffffb0a0089a>] tty_ioctl+0x46a/0x1a10
    [<ffffffffb052db3d>] do_vfs_ioctl+0x5bd/0xc40
    [<ffffffffb052e2f2>] SyS_ioctl+0x132/0x170
    [<ffffffffb11c9b1b>] system_call_fastpath+0x22/0x27
    Memory state around the buggy address:
     ffff8800000fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00
     00 00
     ffff8800000fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00
     00 00 00
    >ffff880000100000: ff ff ff ff ff ff ff ff ff ff ff ff ff
     ff ff ff

It can be reproduce in the linux mainline by the program:
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/ioctl.h>
  #include <linux/vt.h>

  struct tiocl_selection {
    unsigned short xs;      /* X start */
    unsigned short ys;      /* Y start */
    unsigned short xe;      /* X end */
    unsigned short ye;      /* Y end */
    unsigned short sel_mode; /* selection mode */
  };

  #define TIOCL_SETSEL    2
  struct tiocl {
    unsigned char type;
    unsigned char pad;
    struct tiocl_selection sel;
  };

  int main()
  {
    int fd = 0;
    const char *dev = "/dev/char/4:1";

    struct vt_consize v = {0};
    struct tiocl tioc = {0};

    fd = open(dev, O_RDWR, 0);

    v.v_rows = 3346;
    ioctl(fd, VT_RESIZEX, &v);

    tioc.type = TIOCL_SETSEL;
    ioctl(fd, TIOCLINUX, &tioc);

    return 0;
  }

When resize the screen, update the 'vc->vc_size_row' to the new_row_size,
but when 'set_origin' in 'vgacon_set_origin', vgacon use 'vga_vram_base'
for 'vc_origin' and 'vc_visible_origin', not 'vc_screenbuf'. It maybe
smaller than 'vc_screenbuf'. When TIOCLINUX, use the new_row_size to calc
the offset, it maybe larger than the vga_vram_size in vgacon driver, then
bad access.
Also, if set an larger screenbuf firstly, then set an more larger
screenbuf, when copy old_origin to new_origin, a bad access may happen.

So, If the screen size larger than vga_vram, resize screen should be
failed. This alse fix CVE-2020-8649 and CVE-2020-8647.

Fixes: 0aec4867dca14 ("[PATCH] SVGATextMode fix")
Reference: CVE-2020-8647 and CVE-2020-8649
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
---
 drivers/video/console/vgacon.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index de7b8382aba9..998b0de1812f 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -1316,6 +1316,9 @@ static int vgacon_font_get(struct vc_data *c, struct console_font *font)
 static int vgacon_resize(struct vc_data *c, unsigned int width,
 			 unsigned int height, unsigned int user)
 {
+	if ((width << 1) * height > vga_vram_size)
+		return -EINVAL;
+
 	if (width % 2 || width > screen_info.orig_video_cols ||
 	    height > (screen_info.orig_video_lines * vga_default_font_height)/
 	    c->vc_font.height)
-- 
2.17.2

[v4] vgacon: Fix a UAF in vgacon_invert_region

[Zhang Xiaoxu]

When syzkaller tests, there is a UAF:
  BUG: KASan: use after free in vgacon_invert_region+0x9d/0x110 at addr
    ffff880000100000
  Read of size 2 by task syz-executor.1/16489
  page:ffffea0000004000 count:0 mapcount:-127 mapping:          (null)
  index:0x0
  page flags: 0xfffff00000000()
  page dumped because: kasan: bad access detected
  CPU: 1 PID: 16489 Comm: syz-executor.1 Not tainted
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
  rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
  Call Trace:
    [<ffffffffb119f309>] dump_stack+0x1e/0x20
    [<ffffffffb04af957>] kasan_report+0x577/0x950
    [<ffffffffb04ae652>] __asan_load2+0x62/0x80
    [<ffffffffb090f26d>] vgacon_invert_region+0x9d/0x110
    [<ffffffffb0a39d95>] invert_screen+0xe5/0x470
    [<ffffffffb0a21dcb>] set_selection+0x44b/0x12f0
    [<ffffffffb0a3bfae>] tioclinux+0xee/0x490
    [<ffffffffb0a1d114>] vt_ioctl+0xff4/0x2670
    [<ffffffffb0a0089a>] tty_ioctl+0x46a/0x1a10
    [<ffffffffb052db3d>] do_vfs_ioctl+0x5bd/0xc40
    [<ffffffffb052e2f2>] SyS_ioctl+0x132/0x170
    [<ffffffffb11c9b1b>] system_call_fastpath+0x22/0x27
    Memory state around the buggy address:
     ffff8800000fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00
     00 00
     ffff8800000fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00
     00 00 00
    >ffff880000100000: ff ff ff ff ff ff ff ff ff ff ff ff ff
     ff ff ff

It can be reproduce in the linux mainline by the program:
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/ioctl.h>
  #include <linux/vt.h>

  struct tiocl_selection {
    unsigned short xs;      /* X start */
    unsigned short ys;      /* Y start */
    unsigned short xe;      /* X end */
    unsigned short ye;      /* Y end */
    unsigned short sel_mode; /* selection mode */
  };

  #define TIOCL_SETSEL    2
  struct tiocl {
    unsigned char type;
    unsigned char pad;
    struct tiocl_selection sel;
  };

  int main()
  {
    int fd = 0;
    const char *dev = "/dev/char/4:1";

    struct vt_consize v = {0};
    struct tiocl tioc = {0};

    fd = open(dev, O_RDWR, 0);

    v.v_rows = 3346;
    ioctl(fd, VT_RESIZEX, &v);

    tioc.type = TIOCL_SETSEL;
    ioctl(fd, TIOCLINUX, &tioc);

    return 0;
  }

When resize the screen, update the 'vc->vc_size_row' to the new_row_size,
but when 'set_origin' in 'vgacon_set_origin', vgacon use 'vga_vram_base'
for 'vc_origin' and 'vc_visible_origin', not 'vc_screenbuf'. It maybe
smaller than 'vc_screenbuf'. When TIOCLINUX, use the new_row_size to calc
the offset, it maybe larger than the vga_vram_size in vgacon driver, then
bad access.
Also, if set an larger screenbuf firstly, then set an more larger
screenbuf, when copy old_origin to new_origin, a bad access may happen.

So, If the screen size larger than vga_vram, resize screen should be
failed. This alse fix CVE-2020-8649 and CVE-2020-8647.

Fixes: 0aec4867dca14 ("[PATCH] SVGATextMode fix")
Reference: CVE-2020-8647 and CVE-2020-8649
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
---
 drivers/video/console/vgacon.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index de7b8382aba9..998b0de1812f 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -1316,6 +1316,9 @@ static int vgacon_font_get(struct vc_data *c, struct console_font *font)
 static int vgacon_resize(struct vc_data *c, unsigned int width,
 			 unsigned int height, unsigned int user)
 {
+	if ((width << 1) * height > vga_vram_size)
+		return -EINVAL;
+
 	if (width % 2 || width > screen_info.orig_video_cols ||
 	    height > (screen_info.orig_video_lines * vga_default_font_height)/
 	    c->vc_font.height)
-- 
2.17.2

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Daniel Vetter]

On Wed, Mar 04, 2020 at 10:24:29AM +0800, Zhang Xiaoxu wrote:
> When syzkaller tests, there is a UAF:
>   BUG: KASan: use after free in vgacon_invert_region+0x9d/0x110 at addr
>     ffff880000100000
>   Read of size 2 by task syz-executor.1/16489
>   page:ffffea0000004000 count:0 mapcount:-127 mapping:          (null)
>   index:0x0
>   page flags: 0xfffff00000000()
>   page dumped because: kasan: bad access detected
>   CPU: 1 PID: 16489 Comm: syz-executor.1 Not tainted
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>   rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
>   Call Trace:
>     [<ffffffffb119f309>] dump_stack+0x1e/0x20
>     [<ffffffffb04af957>] kasan_report+0x577/0x950
>     [<ffffffffb04ae652>] __asan_load2+0x62/0x80
>     [<ffffffffb090f26d>] vgacon_invert_region+0x9d/0x110
>     [<ffffffffb0a39d95>] invert_screen+0xe5/0x470
>     [<ffffffffb0a21dcb>] set_selection+0x44b/0x12f0
>     [<ffffffffb0a3bfae>] tioclinux+0xee/0x490
>     [<ffffffffb0a1d114>] vt_ioctl+0xff4/0x2670
>     [<ffffffffb0a0089a>] tty_ioctl+0x46a/0x1a10
>     [<ffffffffb052db3d>] do_vfs_ioctl+0x5bd/0xc40
>     [<ffffffffb052e2f2>] SyS_ioctl+0x132/0x170
>     [<ffffffffb11c9b1b>] system_call_fastpath+0x22/0x27
>     Memory state around the buggy address:
>      ffff8800000fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00 00
>      ffff8800000fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00 00 00
>     >ffff880000100000: ff ff ff ff ff ff ff ff ff ff ff ff ff
>      ff ff ff
> 
> It can be reproduce in the linux mainline by the program:
>   #include <stdio.h>
>   #include <stdlib.h>
>   #include <unistd.h>
>   #include <fcntl.h>
>   #include <sys/types.h>
>   #include <sys/stat.h>
>   #include <sys/ioctl.h>
>   #include <linux/vt.h>
> 
>   struct tiocl_selection {
>     unsigned short xs;      /* X start */
>     unsigned short ys;      /* Y start */
>     unsigned short xe;      /* X end */
>     unsigned short ye;      /* Y end */
>     unsigned short sel_mode; /* selection mode */
>   };
> 
>   #define TIOCL_SETSEL    2
>   struct tiocl {
>     unsigned char type;
>     unsigned char pad;
>     struct tiocl_selection sel;
>   };
> 
>   int main()
>   {
>     int fd = 0;
>     const char *dev = "/dev/char/4:1";
> 
>     struct vt_consize v = {0};
>     struct tiocl tioc = {0};
> 
>     fd = open(dev, O_RDWR, 0);
> 
>     v.v_rows = 3346;
>     ioctl(fd, VT_RESIZEX, &v);
> 
>     tioc.type = TIOCL_SETSEL;
>     ioctl(fd, TIOCLINUX, &tioc);
> 
>     return 0;
>   }
> 
> When resize the screen, update the 'vc->vc_size_row' to the new_row_size,
> but when 'set_origin' in 'vgacon_set_origin', vgacon use 'vga_vram_base'
> for 'vc_origin' and 'vc_visible_origin', not 'vc_screenbuf'. It maybe
> smaller than 'vc_screenbuf'. When TIOCLINUX, use the new_row_size to calc
> the offset, it maybe larger than the vga_vram_size in vgacon driver, then
> bad access.
> Also, if set an larger screenbuf firstly, then set an more larger
> screenbuf, when copy old_origin to new_origin, a bad access may happen.
> 
> So, If the screen size larger than vga_vram, resize screen should be
> failed. This alse fix CVE-2020-8649 and CVE-2020-8647.
> 
> Fixes: 0aec4867dca14 ("[PATCH] SVGATextMode fix")
> Reference: CVE-2020-8647 and CVE-2020-8649
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>

This seems to match the size computation used in other places in the vt
and vgacon code. So from that pov

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

There's also no other "is this going to be bigger than the vga memory we
have" checks anywhere, so makes sense to do that. There's a few copy
helpers that limit the copy size to the max of vga_ram_size and
vc->vc_screenbuf_size, but seems like not really done consistently. So
seems to make sense, but really how did I end up getting listed as
maintainer for vt stuff :-/

Anyway also needs

Cc: stable@vger.kernel.org

Linus, since this missed the -fixes pull from Dave maybe double check I'm
not grossly wrong here and apply directly?

Thanks, Daniel

> ---
>  drivers/video/console/vgacon.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> index de7b8382aba9..998b0de1812f 100644
> --- a/drivers/video/console/vgacon.c
> +++ b/drivers/video/console/vgacon.c
> @@ -1316,6 +1316,9 @@ static int vgacon_font_get(struct vc_data *c, struct console_font *font)
>  static int vgacon_resize(struct vc_data *c, unsigned int width,
>  			 unsigned int height, unsigned int user)
>  {
> +	if ((width << 1) * height > vga_vram_size)
> +		return -EINVAL;
> +
>  	if (width % 2 || width > screen_info.orig_video_cols ||
>  	    height > (screen_info.orig_video_lines * vga_default_font_height)/
>  	    c->vc_font.height)
> -- 
> 2.17.2
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Daniel Vetter]

On Wed, Mar 04, 2020 at 10:24:29AM +0800, Zhang Xiaoxu wrote:
> When syzkaller tests, there is a UAF:
>   BUG: KASan: use after free in vgacon_invert_region+0x9d/0x110 at addr
>     ffff880000100000
>   Read of size 2 by task syz-executor.1/16489
>   page:ffffea0000004000 count:0 mapcount:-127 mapping:          (null)
>   index:0x0
>   page flags: 0xfffff00000000()
>   page dumped because: kasan: bad access detected
>   CPU: 1 PID: 16489 Comm: syz-executor.1 Not tainted
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>   rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
>   Call Trace:
>     [<ffffffffb119f309>] dump_stack+0x1e/0x20
>     [<ffffffffb04af957>] kasan_report+0x577/0x950
>     [<ffffffffb04ae652>] __asan_load2+0x62/0x80
>     [<ffffffffb090f26d>] vgacon_invert_region+0x9d/0x110
>     [<ffffffffb0a39d95>] invert_screen+0xe5/0x470
>     [<ffffffffb0a21dcb>] set_selection+0x44b/0x12f0
>     [<ffffffffb0a3bfae>] tioclinux+0xee/0x490
>     [<ffffffffb0a1d114>] vt_ioctl+0xff4/0x2670
>     [<ffffffffb0a0089a>] tty_ioctl+0x46a/0x1a10
>     [<ffffffffb052db3d>] do_vfs_ioctl+0x5bd/0xc40
>     [<ffffffffb052e2f2>] SyS_ioctl+0x132/0x170
>     [<ffffffffb11c9b1b>] system_call_fastpath+0x22/0x27
>     Memory state around the buggy address:
>      ffff8800000fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00 00
>      ffff8800000fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00 00 00
>     >ffff880000100000: ff ff ff ff ff ff ff ff ff ff ff ff ff
>      ff ff ff
> 
> It can be reproduce in the linux mainline by the program:
>   #include <stdio.h>
>   #include <stdlib.h>
>   #include <unistd.h>
>   #include <fcntl.h>
>   #include <sys/types.h>
>   #include <sys/stat.h>
>   #include <sys/ioctl.h>
>   #include <linux/vt.h>
> 
>   struct tiocl_selection {
>     unsigned short xs;      /* X start */
>     unsigned short ys;      /* Y start */
>     unsigned short xe;      /* X end */
>     unsigned short ye;      /* Y end */
>     unsigned short sel_mode; /* selection mode */
>   };
> 
>   #define TIOCL_SETSEL    2
>   struct tiocl {
>     unsigned char type;
>     unsigned char pad;
>     struct tiocl_selection sel;
>   };
> 
>   int main()
>   {
>     int fd = 0;
>     const char *dev = "/dev/char/4:1";
> 
>     struct vt_consize v = {0};
>     struct tiocl tioc = {0};
> 
>     fd = open(dev, O_RDWR, 0);
> 
>     v.v_rows = 3346;
>     ioctl(fd, VT_RESIZEX, &v);
> 
>     tioc.type = TIOCL_SETSEL;
>     ioctl(fd, TIOCLINUX, &tioc);
> 
>     return 0;
>   }
> 
> When resize the screen, update the 'vc->vc_size_row' to the new_row_size,
> but when 'set_origin' in 'vgacon_set_origin', vgacon use 'vga_vram_base'
> for 'vc_origin' and 'vc_visible_origin', not 'vc_screenbuf'. It maybe
> smaller than 'vc_screenbuf'. When TIOCLINUX, use the new_row_size to calc
> the offset, it maybe larger than the vga_vram_size in vgacon driver, then
> bad access.
> Also, if set an larger screenbuf firstly, then set an more larger
> screenbuf, when copy old_origin to new_origin, a bad access may happen.
> 
> So, If the screen size larger than vga_vram, resize screen should be
> failed. This alse fix CVE-2020-8649 and CVE-2020-8647.
> 
> Fixes: 0aec4867dca14 ("[PATCH] SVGATextMode fix")
> Reference: CVE-2020-8647 and CVE-2020-8649
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>

This seems to match the size computation used in other places in the vt
and vgacon code. So from that pov

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

There's also no other "is this going to be bigger than the vga memory we
have" checks anywhere, so makes sense to do that. There's a few copy
helpers that limit the copy size to the max of vga_ram_size and
vc->vc_screenbuf_size, but seems like not really done consistently. So
seems to make sense, but really how did I end up getting listed as
maintainer for vt stuff :-/

Anyway also needs

Cc: stable@vger.kernel.org

Linus, since this missed the -fixes pull from Dave maybe double check I'm
not grossly wrong here and apply directly?

Thanks, Daniel

> ---
>  drivers/video/console/vgacon.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> index de7b8382aba9..998b0de1812f 100644
> --- a/drivers/video/console/vgacon.c
> +++ b/drivers/video/console/vgacon.c
> @@ -1316,6 +1316,9 @@ static int vgacon_font_get(struct vc_data *c, struct console_font *font)
>  static int vgacon_resize(struct vc_data *c, unsigned int width,
>  			 unsigned int height, unsigned int user)
>  {
> +	if ((width << 1) * height > vga_vram_size)
> +		return -EINVAL;
> +
>  	if (width % 2 || width > screen_info.orig_video_cols ||
>  	    height > (screen_info.orig_video_lines * vga_default_font_height)/
>  	    c->vc_font.height)
> -- 
> 2.17.2
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Linus Torvalds]

On Fri, Mar 6, 2020 at 4:38 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> Linus, since this missed the -fixes pull from Dave maybe double check I'm
> not grossly wrong here and apply directly?

Hmm. I don't have the original email, mind just sending it to me (with
the proper added sign-off chain)?

It does strike me that there's nothing that seems to check for
overflow in the "(width << 1) * height" calculation. Hmm?

            Linus

Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Linus Torvalds]

On Fri, Mar 6, 2020 at 4:38 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> Linus, since this missed the -fixes pull from Dave maybe double check I'm
> not grossly wrong here and apply directly?

Hmm. I don't have the original email, mind just sending it to me (with
the proper added sign-off chain)?

It does strike me that there's nothing that seems to check for
overflow in the "(width << 1) * height" calculation. Hmm?

            Linus
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Daniel Vetter]

On Fri, Mar 6, 2020 at 1:55 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Fri, Mar 6, 2020 at 4:38 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> >
> > Linus, since this missed the -fixes pull from Dave maybe double check I'm
> > not grossly wrong here and apply directly?
>
> Hmm. I don't have the original email, mind just sending it to me (with
> the proper added sign-off chain)?

I'll stuff it into a pull and throw that your way, that's simplest.
btw we did add dri-devel to lore a while back, so should be there:

Message-ID: <20200304022429.37738-1-zhangxiaoxu5@huawei.com>
https://lore.kernel.org/dri-devel/20200304022429.37738-1-zhangxiaoxu5@huawei.com/

> It does strike me that there's nothing that seems to check for
> overflow in the "(width << 1) * height" calculation. Hmm?

Indeed I failed to hunt for that :-/ But I think we're good, in
vc_do_resize() we have

    if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
        return -EINVAL;

And they're both (1<<15)-1 so I think should be good enough even on
32bit - I quickly checked and we're short of UINT_MAX:

$ echo $(((((1<<15)-1) << 1)*((1<<15)-1)))
2147352578

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Daniel Vetter]

On Fri, Mar 6, 2020 at 1:55 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Fri, Mar 6, 2020 at 4:38 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> >
> > Linus, since this missed the -fixes pull from Dave maybe double check I'm
> > not grossly wrong here and apply directly?
>
> Hmm. I don't have the original email, mind just sending it to me (with
> the proper added sign-off chain)?

I'll stuff it into a pull and throw that your way, that's simplest.
btw we did add dri-devel to lore a while back, so should be there:

Message-ID: <20200304022429.37738-1-zhangxiaoxu5@huawei.com>
https://lore.kernel.org/dri-devel/20200304022429.37738-1-zhangxiaoxu5@huawei.com/

> It does strike me that there's nothing that seems to check for
> overflow in the "(width << 1) * height" calculation. Hmm?

Indeed I failed to hunt for that :-/ But I think we're good, in
vc_do_resize() we have

    if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
        return -EINVAL;

And they're both (1<<15)-1 so I think should be good enough even on
32bit - I quickly checked and we're short of UINT_MAX:

$ echo $(((((1<<15)-1) << 1)*((1<<15)-1)))
2147352578

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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dri-devel mailing list
dri-devel@lists.freedesktop.org
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Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Linus Torvalds]

On Fri, Mar 6, 2020 at 7:12 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> I'll stuff it into a pull and throw that your way, that's simplest.

Thanks.

> btw we did add dri-devel to lore a while back, so should be there:

Indeed. I tried (incompetently) to look up your message ID, but I
didn't put the dri-devel part and saw the 404, and assumed it wasn't
there.

My bad.

> > It does strike me that there's nothing that seems to check for
> > overflow in the "(width << 1) * height" calculation. Hmm?
>
> Indeed I failed to hunt for that :-/ But I think we're good, in
> vc_do_resize() we have
>
>     if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
>         return -EINVAL;

Perfect. I just looked at the quoted patch itself.

            Linus

Re: [v4] vgacon: Fix a UAF in vgacon_invert_region

[Linus Torvalds]

On Fri, Mar 6, 2020 at 7:12 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> I'll stuff it into a pull and throw that your way, that's simplest.

Thanks.

> btw we did add dri-devel to lore a while back, so should be there:

Indeed. I tried (incompetently) to look up your message ID, but I
didn't put the dri-devel part and saw the 404, and assumed it wasn't
there.

My bad.

> > It does strike me that there's nothing that seems to check for
> > overflow in the "(width << 1) * height" calculation. Hmm?
>
> Indeed I failed to hunt for that :-/ But I think we're good, in
> vc_do_resize() we have
>
>     if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
>         return -EINVAL;

Perfect. I just looked at the quoted patch itself.

            Linus
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