When the bootloader/firmware doesn't setup the framebuffers, their address and size are 0 in "iommu-addresses" property. If IOVA region is reserved with 0 length, then it ends up corrupting the IOVA rbtree with an entry which has pfn_hi < pfn_lo. If we intend to use display driver in kernel without framebuffer then it's causing the display IOMMU mappings to fail as entire valid IOVA space is reserved when address and length are passed as 0. An ideal solution would be firmware removing the "iommu-addresses" property and corresponding "memory-region" if display is not present. But the kernel should be able to handle this by checking for size of IOVA region and skipping the IOVA reservation if size is 0. Also, add a warning if firmware is requesting 0-length IOVA region reservation.
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 2265805]
Issue introduced in 6.3 with commit a5bf3cfce8cb and fixed in 6.6.14 with commit 98b8a550da83 Issue introduced in 6.3 with commit a5bf3cfce8cb and fixed in 6.7.2 with commit 5e23e283910c Issue introduced in 6.3 with commit a5bf3cfce8cb and fixed in 6.8-rc1 with commit bb57f6705960
This was fixed for Fedora with the 6.6.14 stable kernel updates.
The result of automatic check (that is developed by Alexander Larkin) for this CVE-2023-52455 is: CHECK Maybe valid. Check manually. with impact LOW (that is an approximation based on flags WARNONLY SIMPLEFIX IMPROVEONLY ; these flags parsed automatically based on patch data). Such automatic check happens only for Low/Moderates (and only when not from reporter, but parsing already existing CVE). Highs always checked manually (I check it myself and then we check it again in Remediation team). In rare cases some of the Moderates could be increased to High later.