nfsd: initialize copy-notify stateid before publishing it

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nfsd4_copy_notify() finished initializing the cpntf state after
nfs4_alloc_init_cpntf_state() had already linked it into the
s2s_cp_stateids IDR and the parent's sc_cp_list, with cs_count == 1 (the
membership reference) and none held for the caller. A racing
OFFLOAD_CANCEL (crafted cl_id == nn->s2s_cp_cl_id plus the guessable
so_id) could reach manage_cpntf_state() and free the entry, turning the
caller's subsequent cpn_cnr_stateid read and cp_p_stateid/cp_p_clid
writes into use-after-free. The owning clientid was also only recorded
after publication, so it could not gate an ownership check in that window.

Record cp_p_stateid and cp_p_clid inside nfs4_alloc_init_cpntf_state()
before nfs4_init_cp_state() publishes the entry, and return it with an
extra reference. The caller reads the stateid under that reference and
drops it with nfs4_put_cpntf_state(); on a late error the laundromat
reaps the entry.

Fixes: 624322f1ad ("NFSD add COPY_NOTIFY operation")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260710-nfsd-testing-v3-4-a0ff7db6aa3e@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

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This commit is contained in:

Jeff Layton 2026-07-10 10:00:08 -04:00 • committed by Chuck Lever

parent d0beaee498

commit 129643893b

2 changed files with 18 additions and 8 deletions

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16

fs/nfsd/nfs4proc.c

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10

fs/nfsd/nfs4state.c

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