In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/i915: fix incorrect RCU teardown order<\/p>\n
i915_gem_busy_ioctl uses dma_resv_for_each_fence_unlocked() to iterate
\nover the fences in an GEM object without holding a reference but only
\nthe RCU read side lock.<\/p>\n
What can happen here is that the GEM object is destroyed concurrently
\nwhile i915_gem_busy_ioctl is still running. This won’t free the GEM
\nobjects memory, but still drops all the dma_fence references.<\/p>\n
Now when dma_resv_for_each_fence_unlocked() sees a destroyed dma_fence it
\nassumes that a new fence list was installed and re-starts the loop.<\/p>\n
But in the case of a destroyed GEM object a new fence list is never
\ninstalled, only the old one freed and therefore the iteration never
\nfinishes resulting in an endless loop.<\/p>\n
The solution is to drop the fence references only after the RCU grace
\nperiod.<\/p>\n
The fixes tag is not necessary the patch introducing the problem, but the
\none making it so worse that we need to address it.<\/p>\n
This problem was pointed out by Sashiko-bot.<\/p>\n
(cherry picked from commit 5113479556025093bf8133bb2dcaa33be2d50921)<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/i915: fix incorrect RCU teardown order<\/p>\n
i915_gem_busy_ioctl uses dma_resv_for_each_fence_unlocked() to iterate
\nover the fences <\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-40993","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/40993","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=40993"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=40993"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=40993"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}