In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
nfs: use nfsi->rwsem to protect traversal of the file lock list<\/p>\n
Lingfeng identified a bug and suggested two solutions, but both appear
\nto have issues.<\/p>\n
Generally, we cannot release flc_lock while iterating over the file lock
\nlist to avoid use-after-free (UAF) problems with file locks. However,
\nfunctions like nfs_delegation_claim_locks and nfs4_reclaim_locks cannot
\nadhere to this rule because recover_lock or nfs4_lock_delegation_recall
\nmay take a long time. To resolve this, NFS switches to using nfsi->rwsem
\nfor the same protection, and nfs_reclaim_locks follows this approach.
\nAlthough nfs_delegation_claim_locks uses so_delegreturn_mutex instead,
\nthis is inadequate since a single inode can have multiple nfs4_state
\ninstances. Therefore, the fix is to also use nfsi->rwsem in this case.<\/p>\n
Furthermore, after commit c69899a17ca4 (“NFSv4: Update of VFS byte range
\nlock must be atomic with the stateid update”), the functions
\nnfs4_locku_done and nfs4_lock_done also break this rule because they
\ncall locks_lock_inode_wait without holding nfsi->rwsem. Simply adding
\nthis protection could cause many deadlocks, so instead, the call to
\nlocks_lock_inode_wait is moved into _nfs4_proc_setlk. Regarding the bug
\nfixed by commit c69899a17ca4 (“NFSv4: Update of VFS byte range
\nlock must be atomic with the stateid update”), it has been resolved
\nafter commit 0460253913e5 (“NFSv4: nfs4_do_open() is incorrectly triggering
\nstate recovery”) because all slots are drained before calling
\nnfs4_do_reclaim, which prevents concurrent stateid changes along this path.
\nAlso, nfs_delegation_claim_locks does not cause this concurrency either
\nsince when _nfs4_proc_setlk is called with NFS_DELEGATED_STATE, no RPC is
\nsent, so nfs4_lock_done is not called. Therefore,
\nnfs4_lock_delegation_recall from nfs_delegation_claim_locks is the first
\ntime the stateid is set.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
nfs: use nfsi->rwsem to protect traversal of the file lock list<\/p>\n
Lingfeng identified a bug and suggested two solutions, but both ap<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-7141","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/7141","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=7141"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7141"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7141"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}