In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
nfsd: defer vfree of compound ops to fix rpc_status UAF<\/p>\n
The rpc_status netlink dumpit walks every in-flight svc_rqst under
\nrcu_read_lock and, for NFSv4 requests, reads opnums out of
\nargs->ops[]. But args->ops is a separate vmalloc buffer freed
\nsynchronously by vfree() in nfsd4_release_compoundargs() at the end
\nof every compound. The dumpit’s rcu_read_lock pins the svc_rqst
\nstruct itself (freed via kfree_rcu), but nothing defers the vfree
\nof the ops buffer across the RCU grace period. A concurrent compound
\ncompletion can therefore free the buffer while the dumpit is reading
\nit \u2014 a use-after-free on vmalloc memory.<\/p>\n
The trailing seqcount recheck (smp_load_acquire of rq_status_counter)
\ncannot undo a load that already retired against freed memory.<\/p>\n
Fix by replacing vfree(args->ops) with kvfree_rcu_mightsleep(), which
\ndefers the free until after an RCU grace period. This makes the
\nexisting rcu_read_lock in the dumpit sufficient to protect the read.
\nThe tradeoff is that completed compound ops buffers (up to
\n200 * sizeof(struct nfsd4_op)) persist in memory slightly longer,
\nacross one grace period, before being reclaimed.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
nfsd: defer vfree of compound ops to fix rpc_status UAF<\/p>\n
The rpc_status netlink dumpit walks every in-flight svc_rqst under
\nrcu_rea<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-21612","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/21612","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=21612"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21612"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21612"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}