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.
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Affected Vendors & Products
References
History
Wed, 16 Jul 2025 13:45:00 +0000
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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. | |
Title | nfsd: decrease sc_count directly if fail to queue dl_recall | |
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Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-05-26T05:22:43.674Z
Reserved: 2025-04-16T04:51:23.959Z
Link: CVE-2025-37871

No data.

Status : Awaiting Analysis
Published: 2025-05-09T07:16:08.210
Modified: 2025-05-12T17:32:32.760
Link: CVE-2025-37871


No data.