Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:nfsd: decrease sc_count directly if fail to queue dl_recallA deadlock warning occurred when invoking nfs4_put_stid following a faileddl_recall queue operation: T1 T2 nfs4_laundromat nfs4_get_client_reaplist nfs4_anylock_blockers__break_lease spin_lock // ctx->flc_lock spin_lock // clp->cl_lock nfs4_lockowner_has_blockers locks_owner_has_blockers spin_lock // flctx->flc_lock nfsd_break_deleg_cb nfsd_break_one_deleg nfs4_put_stid refcount_dec_and_lock spin_lock // clp->cl_lockWhen a file is opened, an nfs4_delegation is allocated with sc_countinitialized to 1, and the file_lease holds a reference to the delegation.The file_lease is then associated with the file through kernel_setlease.The disassociation is performed in nfsd4_delegreturn via the followingcall chain:nfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg -->nfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_leaseThe corresponding sc_count reference will be released after thisdisassociation.Since nfsd_break_one_deleg executes while holding the flc_lock, thedisassociation process becomes blocked when attempting to acquire flc_lockin generic_delete_lease. This means:1) sc_count in nfsd_break_one_deleg will not be decremented to 0;2) The nfs4_put_stid called by nfsd_break_one_deleg will not attempt toacquire cl_lock;3) Consequently, no deadlock condition is created.Given that sc_count in nfsd_break_one_deleg remains non-zero, we cansafely perform refcount_dec on sc_count directly. This approacheffectively avoids triggering deadlock warnings.
No PoCs from references.
- https://github.com/w4zu/Debian_security