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| author | Zheyu Ma <zheyuma97@gmail.com> | 2022-08-03 12:24:19 +0300 |
|---|---|---|
| committer | Helge Deller <deller@gmx.de> | 2022-08-03 16:15:18 +0300 |
| commit | 40bf722f8064f50200b8c4f8946cd625b441dda9 (patch) | |
| tree | 4bf8cefea0723444218da31b2fd35782585910fb /drivers/video | |
| parent | 2f1c4523f7a3aaabe7e53d3ebd378292947e95c8 (diff) | |
| download | linux-40bf722f8064f50200b8c4f8946cd625b441dda9.tar.xz | |
video: fbdev: i740fb: Check the argument of i740_calc_vclk()
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>
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'drivers/video')
| -rw-r--r-- | drivers/video/fbdev/i740fb.c | 9 |
1 files 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; |