In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
cuse: wait for pending RCU callbacks on module exit<\/p>\n
Since commit 053fc4f755ad (“fuse: fix UAF in rcu pathwalks”),
\nfuse_conn_put() frees the fuse_conn through call_rcu() rather than
\nsynchronously. For cuse, fc->release is cuse_fc_release(), which
\nlives in the cuse module. If the module is removed before the RCU
\ngrace period ends, the callback jumps into freed module memory:<\/p>\n
userspace \/ module unload | RCU softirq
\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\n close(\/dev\/cuse) |
\n cuse_channel_release() |
\n fuse_dev_release() |
\n fuse_conn_put(fch->conn) |
\n call_rcu(delayed_release) ——+—> callback queued
\n |
\n rmmod cuse |
\n cuse_exit() |
\n cuse_channel_destroy() |
\n … |
\n return |
\n |
\n |
\n | rcu_do_batch()
\n | delayed_release()
\n | fc->release()
\n | -> cuse_fc_release()
\n | ^^^ freed text!<\/p>\n
The freed module text is unmapped by vfree(), so the jump into the
\nstale callback triggers a page-fault Oops. If the virtual address
\nis subsequently reused, the callback could execute unrelated code
\n(undefined behaviour).<\/p>\n
Fix this by calling rcu_barrier() in cuse_exit() so that any pending
\nfuse_conn release callback completes before the module is removed.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
cuse: wait for pending RCU callbacks on module exit<\/p>\n
Since commit 053fc4f755ad (“fuse: fix UAF in rcu pathwalks”),
\nfuse_conn_put() <\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-25549","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/25549","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=25549"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25549"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25549"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}