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authorZheyu Ma <zheyuma97@gmail.com>2022-08-03 12:23:12 +0300
committerHelge Deller <deller@gmx.de>2022-08-03 16:13:15 +0300
commit2f1c4523f7a3aaabe7e53d3ebd378292947e95c8 (patch)
treead21f8e75f6d09410e326f4bf9c78f194449e91d
parentc5c7502e960d9128eae1a5663fb62506d8685ac3 (diff)
downloadlinux-2f1c4523f7a3aaabe7e53d3ebd378292947e95c8.tar.xz
video: fbdev: arkfb: Fix a divide-by-zero bug in ark_set_pixclock()
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>
-rw-r--r--drivers/video/fbdev/arkfb.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c
index eb3e47c58c5f..ed76ddc7df3d 100644
--- a/drivers/video/fbdev/arkfb.c
+++ b/drivers/video/fbdev/arkfb.c
@@ -781,7 +781,12 @@ 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,