{"id":24476,"date":"2026-09-16T20:32:22","date_gmt":"2026-09-16T12:32:22","guid":{"rendered":"https:\/\/www.54iter.cn\/?vuln=cve-2026-89793"},"modified":"2026-09-16T20:32:22","modified_gmt":"2026-09-16T12:32:22","slug":"cve-2026-89793","status":"publish","type":"vuln","link":"https:\/\/www.54iter.cn\/?vuln=cve-2026-89793","title":{"rendered":"CVE-2026-89793 &#8211; In the Linux kernel, the following vulnerability has been resolved:\n\nublk: clear VM_MAYWRI"},"content":{"rendered":"<p>In the Linux kernel, the following vulnerability has been resolved:<\/p>\n<p>ublk: clear VM_MAYWRITE on read-only ublk char device mmap<\/p>\n<p>ublk_ch_mmap() rejects mmap requests with VM_WRITE set, but never<br \/>\nclears VM_MAYWRITE on the resulting read-only mapping. This allows<br \/>\na userspace daemon to mmap the per-queue command buffer PROT_READ,<br \/>\nthen upgrade it to PROT_WRITE via mprotect(), since VM_MAYWRITE was<br \/>\nnever cleared.<\/p>\n<p>The command buffer holds struct ublksrv_io_desc entries that are<br \/>\nkernel-written ABI; a writable mapping lets an unprivileged daemon<br \/>\nprocess corrupt fields such as addr, op_flags, nr_sectors, and<br \/>\nstart_sector.<\/p>\n<p>Same bug class as the drm\/panthor and drm\/vc4 VM_MAYWRITE fixes, and<br \/>\nthe 2026-08-13 ptp\/vmclock fix (a5edadbae57e).<\/p>\n<p>Verified via mprotect() PoC: before the fix, a PROT_READ mapping can<br \/>\nbe upgraded to PROT_READ|PROT_WRITE and a write into the command<br \/>\nbuffer corrupts io_desc fields (confirmed under KASAN). After the<br \/>\nfix, mprotect() returns -EACCES.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In the Linux kernel, the following vulnerability has been resolved:<\/p>\n<p>ublk: clear VM_MAYWRITE on read-only ublk char device mmap<\/p>\n<p>ublk_ch_mmap() rejects mmap requests with VM_WRITE set, but never<br \/>\nclear<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-24476","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/24476","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=24476"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=24476"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=24476"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}