fbdev: core: fbcvt: avoid division by 0 in fb_cvt_hperiod()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: fbdev: core: fbcvt: avoid division by 0 in fb_cvt_hperiod() In fb_find_mode_cvt(), iff mode->refresh somehow happens to be 0x80000000, cvt.f_refresh will become 0 when multiplying it by 2 due to overflow. It's then passed to fb_cvt_hperiod(), where it's used as a divider -- division by 0 will result in kernel oops. Add a sanity check for cvt.f_refresh to avoid such overflow... Found by Linux Verification Center (linuxtesting.org) with the Svace static analysis tool.

References

• https://git.kernel.org/stable/c/9027ce4c037b566b658b8939a76326b7125e3627
• https://git.kernel.org/stable/c/610f247f2772e4f92b63442125a1b7ade79898d8
• https://git.kernel.org/stable/c/2d63433e8eaa3c91b2948190e395bc67009db0d9
• https://git.kernel.org/stable/c/54947530663edcbaaee1314c01fdd8c72861b124
• https://git.kernel.org/stable/c/ab91647acdf43b984824776559a452212eaeb21a
• https://git.kernel.org/stable/c/b235393b9f43ff86a38ca2bde6372312ea215dc5
• https://git.kernel.org/stable/c/53784073cbad18f75583fd3da9ffdfc4d1f05405
• https://git.kernel.org/stable/c/3f6dae09fc8c306eb70fdfef70726e1f154e173a