| Message ID | 20220803092419.2821723-1-zheyuma97@gmail.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | video: fbdev: i740fb: Check the argument of i740_calc_vclk() | expand |
On 8/3/22 11:24, Zheyu Ma wrote: > 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. > > If the user provides an improper 'pixclock' value that makes the argumet > of i740_calc_vclk() less than 'I740_RFREQ_FIX', it will cause a > divide-by-zero bug in: > drivers/video/fbdev/i740fb.c:353 p_best = min(15, ilog2(I740_MAX_VCO_FREQ / (freq / I740_RFREQ_FIX))); > > The following log can reveal it: > > divide error: 0000 [#1] PREEMPT SMP KASAN PTI > RIP: 0010:i740_calc_vclk drivers/video/fbdev/i740fb.c:353 [inline] > RIP: 0010:i740fb_decode_var drivers/video/fbdev/i740fb.c:646 [inline] > RIP: 0010:i740fb_set_par+0x163f/0x3b70 drivers/video/fbdev/i740fb.c:742 > 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 i740_calc_vclk() first. > > Signed-off-by: Zheyu Ma <zheyuma97@gmail.com> applied to fbdev git tree. Thanks! Helge > --- > drivers/video/fbdev/i740fb.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/video/fbdev/i740fb.c b/drivers/video/fbdev/i740fb.c > index 09dd85553d4f..7f09a0daaaa2 100644 > --- a/drivers/video/fbdev/i740fb.c > +++ b/drivers/video/fbdev/i740fb.c > @@ -400,7 +400,7 @@ static int i740fb_decode_var(const struct fb_var_screeninfo *var, > u32 xres, right, hslen, left, xtotal; > u32 yres, lower, vslen, upper, ytotal; > u32 vxres, xoffset, vyres, yoffset; > - u32 bpp, base, dacspeed24, mem; > + u32 bpp, base, dacspeed24, mem, freq; > u8 r7; > int i; > > @@ -643,7 +643,12 @@ static int i740fb_decode_var(const struct fb_var_screeninfo *var, > par->atc[VGA_ATC_OVERSCAN] = 0; > > /* Calculate VCLK that most closely matches the requested dot clock */ > - i740_calc_vclk((((u32)1e9) / var->pixclock) * (u32)(1e3), par); > + freq = (((u32)1e9) / var->pixclock) * (u32)(1e3); > + if (freq < I740_RFREQ_FIX) { > + fb_dbg(info, "invalid pixclock\n"); > + freq = I740_RFREQ_FIX; > + } > + i740_calc_vclk(freq, par); > > /* Since we program the clocks ourselves, always use VCLK2. */ > par->misc |= 0x0C;
diff --git a/drivers/video/fbdev/i740fb.c b/drivers/video/fbdev/i740fb.c index 09dd85553d4f..7f09a0daaaa2 100644 --- a/drivers/video/fbdev/i740fb.c +++ b/drivers/video/fbdev/i740fb.c @@ -400,7 +400,7 @@ static int i740fb_decode_var(const struct fb_var_screeninfo *var, u32 xres, right, hslen, left, xtotal; u32 yres, lower, vslen, upper, ytotal; u32 vxres, xoffset, vyres, yoffset; - u32 bpp, base, dacspeed24, mem; + u32 bpp, base, dacspeed24, mem, freq; u8 r7; int i; @@ -643,7 +643,12 @@ static int i740fb_decode_var(const struct fb_var_screeninfo *var, par->atc[VGA_ATC_OVERSCAN] = 0; /* Calculate VCLK that most closely matches the requested dot clock */ - i740_calc_vclk((((u32)1e9) / var->pixclock) * (u32)(1e3), par); + freq = (((u32)1e9) / var->pixclock) * (u32)(1e3); + if (freq < I740_RFREQ_FIX) { + fb_dbg(info, "invalid pixclock\n"); + freq = I740_RFREQ_FIX; + } + i740_calc_vclk(freq, par); /* Since we program the clocks ourselves, always use VCLK2. */ par->misc |= 0x0C;
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. If the user provides an improper 'pixclock' value that makes the argumet of i740_calc_vclk() less than 'I740_RFREQ_FIX', it will cause a divide-by-zero bug in: drivers/video/fbdev/i740fb.c:353 p_best = min(15, ilog2(I740_MAX_VCO_FREQ / (freq / I740_RFREQ_FIX))); The following log can reveal it: divide error: 0000 [#1] PREEMPT SMP KASAN PTI RIP: 0010:i740_calc_vclk drivers/video/fbdev/i740fb.c:353 [inline] RIP: 0010:i740fb_decode_var drivers/video/fbdev/i740fb.c:646 [inline] RIP: 0010:i740fb_set_par+0x163f/0x3b70 drivers/video/fbdev/i740fb.c:742 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 i740_calc_vclk() first. Signed-off-by: Zheyu Ma <zheyuma97@gmail.com> --- drivers/video/fbdev/i740fb.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)