CVE-2025-37871

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: decrease sc_count directly if fail to queue dl_recall A deadlock warning occurred when invoking nfs4_put_stid following a failed dl_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_lock When a file is opened, an nfs4_delegation is allocated with sc_count initialized 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 following call chain: nfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg --> nfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_lease The corresponding sc_count reference will be released after this disassociation. Since nfsd_break_one_deleg executes while holding the flc_lock, the disassociation process becomes blocked when attempting to acquire flc_lock in 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 to acquire cl_lock; 3) Consequently, no deadlock condition is created. Given that sc_count in nfsd_break_one_deleg remains non-zero, we can safely perform refcount_dec on sc_count directly. This approach effectively avoids triggering deadlock warnings.

Gravité et risque d'exploitation

CVE-2025-37871 obtient un score CVSS de 7.5/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.78 %, ce qui la place devant 55.1 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <5.15.181, 5.15.180, b874cdef4e67e5150e07eff0eae1cbb21fb92da1, <14985d66b9b99c12995dd99d1c6c8dec4114c2a5, cdb796137c57e68ca34518d53be53b679351eb86, <6.14.4, <a1d14d931bf700c1025db8c46d6731aa5cf440f9, 6.14.2, 6.1.134, <ba903539fff745d592d893c71b30e5e268a95413, 6.6.87, <a7fce086f6ca84db409b9d58493ea77c1978897c, 230ca758453c63bd38e4d9f4a21db698f7abada8, 6.13.11, d96587cc93ec369031bcd7658c6adc719873c9fd, 6.12.23, <b9bbe8f9d5663311d06667ce36d6ed255ead1a26, <a70832d3555987035fc430ccd703acd89393eadb, 9a81cde8c7ce65dd90fb47ceea93a45fc1a2fbd1, cad3479b63661a399c9df1d0b759e1806e2df3c8, 5.10.236, 63b91c8ff4589f5263873b24c052447a28e10ef7, <6.14, <6.6.88, 133f5e2a37ce08c82d24e8fba65e0a81deae4609, <5.10.237, <6.12.25, <6.1.135, <7d192e27a431026c58d60edf66dc6cd98d0c01fc) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/b9bbe8f9d5663311d06667ce36d6ed255ead1a26
• https://git.kernel.org/stable/c/a70832d3555987035fc430ccd703acd89393eadb
• https://git.kernel.org/stable/c/ba903539fff745d592d893c71b30e5e268a95413
• https://git.kernel.org/stable/c/7d192e27a431026c58d60edf66dc6cd98d0c01fc
• https://git.kernel.org/stable/c/a7fce086f6ca84db409b9d58493ea77c1978897c
• https://git.kernel.org/stable/c/14985d66b9b99c12995dd99d1c6c8dec4114c2a5
• https://git.kernel.org/stable/c/a1d14d931bf700c1025db8c46d6731aa5cf440f9