From: Zheyu Ma zheyuma97@gmail.com
[ Upstream commit 2f1c4523f7a3aaabe7e53d3ebd378292947e95c8 ]
Since the user can control the arguments of the ioctl() from the user space, under special arguments that may result in a divide-by-zero bug in: drivers/video/fbdev/arkfb.c:784: ark_set_pixclock(info, (hdiv * info->var.pixclock) / hmul); with hdiv=1, pixclock=1 and hmul=2 you end up with (1*1)/2 = (int) 0. and then in: drivers/video/fbdev/arkfb.c:504: rv = dac_set_freq(par->dac, 0, 1000000000 / pixclock); we'll get a division-by-zero.
The following log can reveal it:
divide error: 0000 [#1] PREEMPT SMP KASAN PTI RIP: 0010:ark_set_pixclock drivers/video/fbdev/arkfb.c:504 [inline] RIP: 0010:arkfb_set_par+0x10fc/0x24c0 drivers/video/fbdev/arkfb.c:784 Call Trace: fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1034 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189
Fix this by checking the argument of ark_set_pixclock() first.
Fixes: 681e14730c73 ("arkfb: new framebuffer driver for ARK Logic cards") Signed-off-by: Zheyu Ma zheyuma97@gmail.com Signed-off-by: Helge Deller deller@gmx.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/arkfb.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c index 13ba371e70aa..bfa221b68d71 100644 --- a/drivers/video/fbdev/arkfb.c +++ b/drivers/video/fbdev/arkfb.c @@ -778,7 +778,12 @@ static int arkfb_set_par(struct fb_info *info) return -EINVAL; }
- ark_set_pixclock(info, (hdiv * info->var.pixclock) / hmul); + value = (hdiv * info->var.pixclock) / hmul; + if (!value) { + fb_dbg(info, "invalid pixclock\n"); + value = 1; + } + ark_set_pixclock(info, value); svga_set_timings(par->state.vgabase, &ark_timing_regs, &(info->var), hmul, hdiv, (info->var.vmode & FB_VMODE_DOUBLE) ? 2 : 1, (info->var.vmode & FB_VMODE_INTERLACED) ? 2 : 1,