CVE-2025-38312

In the Linux kernel, the following vulnerability has been resolved:

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

In fbfindmodecvt(), iff mode->refresh somehow happens to be 0x80000000, cvt.frefresh will become 0 when multiplying it by 2 due to overflow. It's then passed to fbcvthperiod(), 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.