6.15-stable review patch. If anyone has any objections, please let me know.
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From: Sravan Kumar Gundu sravankumarlpu@gmail.com
commit af0db3c1f898144846d4c172531a199bb3ca375d upstream.
This issue triggers when a userspace program does an ioctl FBIOPUT_CON2FBMAP by passing console number and frame buffer number. Ideally this maps console to frame buffer and updates the screen if console is visible.
As part of mapping it has to do resize of console according to frame buffer info. if this resize fails and returns from vc_do_resize() and continues further. At this point console and new frame buffer are mapped and sets display vars. Despite failure still it continue to proceed updating the screen at later stages where vc_data is related to previous frame buffer and frame buffer info and display vars are mapped to new frame buffer and eventully leading to out-of-bounds write in fast_imageblit(). This bheviour is excepted only when fg_console is equal to requested console which is a visible console and updates screen with invalid struct references in fbcon_putcs().
Reported-and-tested-by: syzbot+c4b7aa0513823e2ea880@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c4b7aa0513823e2ea880 Signed-off-by: Sravan Kumar Gundu sravankumarlpu@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Helge Deller deller@gmx.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/video/fbdev/core/fbcon.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
--- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -825,7 +825,8 @@ static void con2fb_init_display(struct v fg_vc->vc_rows); }
- update_screen(vc_cons[fg_console].d); + if (fg_console != unit) + update_screen(vc_cons[fg_console].d); }
/** @@ -1362,6 +1363,7 @@ static void fbcon_set_disp(struct fb_inf struct vc_data *svc; struct fbcon_ops *ops = info->fbcon_par; int rows, cols; + unsigned long ret = 0;
p = &fb_display[unit];
@@ -1412,11 +1414,10 @@ static void fbcon_set_disp(struct fb_inf rows = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres); cols /= vc->vc_font.width; rows /= vc->vc_font.height; - vc_resize(vc, cols, rows); + ret = vc_resize(vc, cols, rows);
- if (con_is_visible(vc)) { + if (con_is_visible(vc) && !ret) update_screen(vc); - } }
static __inline__ void ywrap_up(struct vc_data *vc, int count)