Hi,
This is a minor update to the previous version of the series, adding a
clarification to 3/3 as to the problem the original fix to which caused
the functional regression the removal of extra VT_RESIZEX parameter
handling caused. No change to actual code.
See individual change descriptions for details.
Please apply.
Maciej
Revert the removal of code handling extra VT_RESIZEX ioctl's parameters
beyond those that VT_RESIZE supports, fixing a functional regression
causing `svgatextmode' not to resize the VT anymore. As a consequence
of the reverted change when the video adapter is reprogrammed from the
original say 80x25 text mode using a 9x16 character cell (720x400 pixel
resolution) to say 80x37 text mode and the same character cell (720x592
pixel resolution), the VT geometry does not get updated and only upper
two thirds of the screen are used for the VT, and the lower part remains
blank. The proportions change according to text mode geometries chosen.
Revert the change verbatim then, bringing back previous VT resizing.
Signed-off-by: Maciej W. Rozycki <[email protected]>
Fixes: 988d0763361b ("vt_ioctl: make VT_RESIZEX behave like VT_RESIZE")
Cc: [email protected] # v5.10+
---
No changes from v1.
---
drivers/tty/vt/vt_ioctl.c | 57 +++++++++++++++++++++++++++++++++++++---------
1 file changed, 47 insertions(+), 10 deletions(-)
Index: linux-macro-ide/drivers/tty/vt/vt_ioctl.c
===================================================================
--- linux-macro-ide.orig/drivers/tty/vt/vt_ioctl.c
+++ linux-macro-ide/drivers/tty/vt/vt_ioctl.c
@@ -671,21 +671,58 @@ static int vt_resizex(struct vc_data *vc
if (copy_from_user(&v, cs, sizeof(struct vt_consize)))
return -EFAULT;
- if (v.v_vlin)
- pr_info_once("\"struct vt_consize\"->v_vlin is ignored. Please report if you need this.\n");
- if (v.v_clin)
- pr_info_once("\"struct vt_consize\"->v_clin is ignored. Please report if you need this.\n");
+ /* FIXME: Should check the copies properly */
+ if (!v.v_vlin)
+ v.v_vlin = vc->vc_scan_lines;
+
+ if (v.v_clin) {
+ int rows = v.v_vlin / v.v_clin;
+ if (v.v_rows != rows) {
+ if (v.v_rows) /* Parameters don't add up */
+ return -EINVAL;
+ v.v_rows = rows;
+ }
+ }
+
+ if (v.v_vcol && v.v_ccol) {
+ int cols = v.v_vcol / v.v_ccol;
+ if (v.v_cols != cols) {
+ if (v.v_cols)
+ return -EINVAL;
+ v.v_cols = cols;
+ }
+ }
+
+ if (v.v_clin > 32)
+ return -EINVAL;
- console_lock();
for (i = 0; i < MAX_NR_CONSOLES; i++) {
- vc = vc_cons[i].d;
+ struct vc_data *vcp;
- if (vc) {
- vc->vc_resize_user = 1;
- vc_resize(vc, v.v_cols, v.v_rows);
+ if (!vc_cons[i].d)
+ continue;
+ console_lock();
+ vcp = vc_cons[i].d;
+ if (vcp) {
+ int ret;
+ int save_scan_lines = vcp->vc_scan_lines;
+ int save_font_height = vcp->vc_font.height;
+
+ if (v.v_vlin)
+ vcp->vc_scan_lines = v.v_vlin;
+ if (v.v_clin)
+ vcp->vc_font.height = v.v_clin;
+ vcp->vc_resize_user = 1;
+ ret = vc_resize(vcp, v.v_cols, v.v_rows);
+ if (ret) {
+ vcp->vc_scan_lines = save_scan_lines;
+ vcp->vc_font.height = save_font_height;
+ console_unlock();
+ return ret;
+ }
}
+ console_unlock();
}
- console_unlock();
return 0;
}
Restore the original intent of the VT_RESIZEX ioctl's `v_clin' parameter
which is the number of pixel rows per character (cell) rather than the
height of the font used.
For framebuffer devices the two values are always the same, because the
former is inferred from the latter one. For VGA used as a true text
mode device these two parameters are independent from each other: the
number of pixel rows per character is set in the CRT controller, while
font height is in fact hardwired to 32 pixel rows and fonts of heights
below that value are handled by padding their data with blanks when
loaded to hardware for use by the character generator. One can change
the setting in the CRT controller and it will update the screen contents
accordingly regardless of the font loaded.
The `v_clin' parameter is used by the `vgacon' driver to set the height
of the character cell and then the cursor position within. Make the
parameter explicit then, by defining a new `vc_cell_height' struct
member of `vc_data', set it instead of `vc_font.height' from `v_clin' in
the VT_RESIZEX ioctl, and then use it throughout the `vgacon' driver
except where actual font data is accessed which as noted above is
independent from the CRTC setting.
This way the framebuffer console driver is free to ignore the `v_clin'
parameter as irrelevant, as it always should have, avoiding any issues
attempts to give the parameter a meaning there could have caused, such
as one that has led to commit 988d0763361b ("vt_ioctl: make VT_RESIZEX
behave like VT_RESIZE"):
"syzbot is reporting UAF/OOB read at bit_putcs()/soft_cursor() [1][2], for
vt_resizex() from ioctl(VT_RESIZEX) allows setting font height larger than
actual font height calculated by con_font_set() from ioctl(PIO_FONT).
Since fbcon_set_font() from con_font_set() allocates minimal amount of
memory based on actual font height calculated by con_font_set(),
use of vt_resizex() can cause UAF/OOB read for font data."
The problem first appeared around Linux 2.5.66 which predates our repo
history, but the origin could be identified with the old MIPS/Linux repo
also at: <git://git.kernel.org/pub/scm/linux/kernel/git/ralf/linux.git>
as commit 9736a3546de7 ("Merge with Linux 2.5.66."), where VT_RESIZEX
code in `vt_ioctl' was updated as follows:
if (clin)
- video_font_height = clin;
+ vc->vc_font.height = clin;
making the parameter apply to framebuffer devices as well, perhaps due
to the use of "font" in the name of the original `video_font_height'
variable. Use "cell" in the new struct member then to avoid ambiguity.
References:
[1] https://syzkaller.appspot.com/bug?id=32577e96d88447ded2d3b76d71254fb855245837
[2] https://syzkaller.appspot.com/bug?id=6b8355d27b2b94fb5cedf4655e3a59162d9e48e3
Signed-off-by: Maciej W. Rozycki <[email protected]>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: [email protected] # v2.6.12+
---
Changes from v1:
- Clarification added as to the previous attempt to fix a problem in
framebuffer triggered with the VT_RESIZEX ioctl.
---
drivers/tty/vt/vt_ioctl.c | 6 ++---
drivers/video/console/vgacon.c | 44 ++++++++++++++++++++---------------------
include/linux/console_struct.h | 1
3 files changed, 26 insertions(+), 25 deletions(-)
Index: linux-macro-ide/drivers/tty/vt/vt_ioctl.c
===================================================================
--- linux-macro-ide.orig/drivers/tty/vt/vt_ioctl.c
+++ linux-macro-ide/drivers/tty/vt/vt_ioctl.c
@@ -706,17 +706,17 @@ static int vt_resizex(struct vc_data *vc
if (vcp) {
int ret;
int save_scan_lines = vcp->vc_scan_lines;
- int save_font_height = vcp->vc_font.height;
+ int save_cell_height = vcp->vc_cell_height;
if (v.v_vlin)
vcp->vc_scan_lines = v.v_vlin;
if (v.v_clin)
- vcp->vc_font.height = v.v_clin;
+ vcp->vc_cell_height = v.v_clin;
vcp->vc_resize_user = 1;
ret = vc_resize(vcp, v.v_cols, v.v_rows);
if (ret) {
vcp->vc_scan_lines = save_scan_lines;
- vcp->vc_font.height = save_font_height;
+ vcp->vc_cell_height = save_cell_height;
console_unlock();
return ret;
}
Index: linux-macro-ide/drivers/video/console/vgacon.c
===================================================================
--- linux-macro-ide.orig/drivers/video/console/vgacon.c
+++ linux-macro-ide/drivers/video/console/vgacon.c
@@ -383,7 +383,7 @@ static void vgacon_init(struct vc_data *
vc_resize(c, vga_video_num_columns, vga_video_num_lines);
c->vc_scan_lines = vga_scan_lines;
- c->vc_font.height = vga_video_font_height;
+ c->vc_font.height = c->vc_cell_height = vga_video_font_height;
c->vc_complement_mask = 0x7700;
if (vga_512_chars)
c->vc_hi_font_mask = 0x0800;
@@ -518,32 +518,32 @@ static void vgacon_cursor(struct vc_data
switch (CUR_SIZE(c->vc_cursor_type)) {
case CUR_UNDERLINE:
vgacon_set_cursor_size(c->state.x,
- c->vc_font.height -
- (c->vc_font.height <
+ c->vc_cell_height -
+ (c->vc_cell_height <
10 ? 2 : 3),
- c->vc_font.height -
- (c->vc_font.height <
+ c->vc_cell_height -
+ (c->vc_cell_height <
10 ? 1 : 2));
break;
case CUR_TWO_THIRDS:
vgacon_set_cursor_size(c->state.x,
- c->vc_font.height / 3,
- c->vc_font.height -
- (c->vc_font.height <
+ c->vc_cell_height / 3,
+ c->vc_cell_height -
+ (c->vc_cell_height <
10 ? 1 : 2));
break;
case CUR_LOWER_THIRD:
vgacon_set_cursor_size(c->state.x,
- (c->vc_font.height * 2) / 3,
- c->vc_font.height -
- (c->vc_font.height <
+ (c->vc_cell_height * 2) / 3,
+ c->vc_cell_height -
+ (c->vc_cell_height <
10 ? 1 : 2));
break;
case CUR_LOWER_HALF:
vgacon_set_cursor_size(c->state.x,
- c->vc_font.height / 2,
- c->vc_font.height -
- (c->vc_font.height <
+ c->vc_cell_height / 2,
+ c->vc_cell_height -
+ (c->vc_cell_height <
10 ? 1 : 2));
break;
case CUR_NONE:
@@ -554,7 +554,7 @@ static void vgacon_cursor(struct vc_data
break;
default:
vgacon_set_cursor_size(c->state.x, 1,
- c->vc_font.height);
+ c->vc_cell_height);
break;
}
break;
@@ -565,13 +565,13 @@ static int vgacon_doresize(struct vc_dat
unsigned int width, unsigned int height)
{
unsigned long flags;
- unsigned int scanlines = height * c->vc_font.height;
+ unsigned int scanlines = height * c->vc_cell_height;
u8 scanlines_lo = 0, r7 = 0, vsync_end = 0, mode, max_scan;
raw_spin_lock_irqsave(&vga_lock, flags);
vgacon_xres = width * VGA_FONTWIDTH;
- vgacon_yres = height * c->vc_font.height;
+ vgacon_yres = height * c->vc_cell_height;
if (vga_video_type >= VIDEO_TYPE_VGAC) {
outb_p(VGA_CRTC_MAX_SCAN, vga_video_port_reg);
max_scan = inb_p(vga_video_port_val);
@@ -626,9 +626,9 @@ static int vgacon_doresize(struct vc_dat
static int vgacon_switch(struct vc_data *c)
{
int x = c->vc_cols * VGA_FONTWIDTH;
- int y = c->vc_rows * c->vc_font.height;
+ int y = c->vc_rows * c->vc_cell_height;
int rows = screen_info.orig_video_lines * vga_default_font_height/
- c->vc_font.height;
+ c->vc_cell_height;
/*
* We need to save screen size here as it's the only way
* we can spot the screen has been resized and we need to
@@ -1041,7 +1041,7 @@ static int vgacon_adjust_height(struct v
cursor_size_lastto = 0;
c->vc_sw->con_cursor(c, CM_DRAW);
}
- c->vc_font.height = fontheight;
+ c->vc_font.height = c->vc_cell_height = fontheight;
vc_resize(c, 0, rows); /* Adjust console size */
}
}
@@ -1096,12 +1096,12 @@ static int vgacon_resize(struct vc_data
*/
screen_info.orig_video_cols = width;
screen_info.orig_video_lines = height;
- vga_default_font_height = c->vc_font.height;
+ vga_default_font_height = c->vc_cell_height;
return 0;
}
if (width % 2 || width > screen_info.orig_video_cols ||
height > (screen_info.orig_video_lines * vga_default_font_height)/
- c->vc_font.height)
+ c->vc_cell_height)
return -EINVAL;
if (con_is_visible(c) && !vga_is_gfx) /* who knows */
Index: linux-macro-ide/include/linux/console_struct.h
===================================================================
--- linux-macro-ide.orig/include/linux/console_struct.h
+++ linux-macro-ide/include/linux/console_struct.h
@@ -101,6 +101,7 @@ struct vc_data {
unsigned int vc_rows;
unsigned int vc_size_row; /* Bytes per row */
unsigned int vc_scan_lines; /* # of scan lines */
+ unsigned int vc_cell_height; /* CRTC character cell height */
unsigned long vc_origin; /* [!] Start of real screen */
unsigned long vc_scr_end; /* [!] End of real screen */
unsigned long vc_visible_origin; /* [!] Top of visible window */
Fix an issue with VGA console font size changes made after the initial
video text mode has been changed with a user tool like `svgatextmode'
calling the VT_RESIZEX ioctl. As it stands in that case the original
screen geometry continues being used to validate further VT resizing.
Consequently when the video adapter is firstly reprogrammed from the
original say 80x25 text mode using a 9x16 character cell (720x400 pixel
resolution) to say 80x37 text mode and the same character cell (720x592
pixel resolution), and secondly the CRTC character cell updated to 9x8
(by loading a suitable font with the KD_FONT_OP_SET request of the
KDFONTOP ioctl), the VT geometry does not get further updated from 80x37
and only upper half of the screen is used for the VT, with the lower
half showing rubbish corresponding to whatever happens to be there in
the video memory that maps to that part of the screen. Of course the
proportions change according to text mode geometries and font sizes
chosen.
Address the problem then, by updating the text mode geometry defaults
rather than checking against them whenever the VT is resized via a user
ioctl.
Signed-off-by: Maciej W. Rozycki <[email protected]>
Fixes: e400b6ec4ede ("vt/vgacon: Check if screen resize request comes from userspace")
Cc: [email protected] # v2.6.24+
---
No changes from v1.
---
drivers/video/console/vgacon.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
Index: linux-macro-ide/drivers/video/console/vgacon.c
===================================================================
--- linux-macro-ide.orig/drivers/video/console/vgacon.c
+++ linux-macro-ide/drivers/video/console/vgacon.c
@@ -1089,12 +1089,20 @@ static int vgacon_resize(struct vc_data
if ((width << 1) * height > vga_vram_size)
return -EINVAL;
+ if (user) {
+ /*
+ * Ho ho! Someone (svgatextmode, eh?) may have reprogrammed
+ * the video mode! Set the new defaults then and go away.
+ */
+ screen_info.orig_video_cols = width;
+ screen_info.orig_video_lines = height;
+ vga_default_font_height = c->vc_font.height;
+ return 0;
+ }
if (width % 2 || width > screen_info.orig_video_cols ||
height > (screen_info.orig_video_lines * vga_default_font_height)/
c->vc_font.height)
- /* let svgatextmode tinker with video timings and
- return success */
- return (user) ? 0 : -EINVAL;
+ return -EINVAL;
if (con_is_visible(c) && !vga_is_gfx) /* who knows */
vgacon_doresize(c, width, height);