kernel/linux.git/fs/lockd/svc4proc.c, branch linux-7.1.y

lockd: fix TEST handling when not all permissions are available.

2026-05-21T21:08:47+00:00

The F_GETLK fcntl can work with either read access or write access or both. It can query F_RDLCK and F_WRLCK locks in either case. However lockd currently treats F_GETLK similar to F_SETLK in that read access is required to query an F_RDLCK lock and write access is required to query a F_WRLCK lock. This is wrong and can cause problems - e.g. when qemu accesses a read-only (e.g. iso) filesystem image over NFS (though why it queries if it can get a write lock - I don't know. But it does, and this works with local filesystems). So we need TEST requests to be handled differently. To do this: - change nlm_do_fopen() to accept O_RDWR as a mode and in that case succeed if either a O_RDONLY or O_WRONLY file can be opened. - change nlm_lookup_file() to accept a mode argument from caller, instead of deducing base on lock time, and pass that on to nlm_do_fopen() - change nlm4svc_retrieve_args() and nlmsvc_retrieve_args() to detect TEST requests and pass O_RDWR as a mode to nlm_lookup_file, passing the same mode as before for other requests. Also set lock->fl.c.flc_file to whichever file is available for TEST requests. - change nlmsvc_testlock() to also not calculate the mode, but to use whatever was stored in lock->fl.c.flc_file. This behaviour of lockd - requesting O_WRONLY access to TEST for exclusive locks - has been present at least since git history began. However it was hidden until recently because knfsd ignored the access requested by lockd and required only READ access for all locking requests (unless the underlying filesystem provided an f_op->open function which checked access permissions). The commit mentioned in Fixes: below changed nfsd_permission() to NOT override the access request for LOCK requests and this exposed the bug that we are now fixing. Note that there is another issue that this patch does not address. The flock(.., LOCK_EX) call is permitted on a read-only file descriptor. Linux NFS maps this to NLM locking as whole-file byte-range locks. nfsd will see this as though it were fcntl( F_SETLK (F_WRLCK)) and will now require write access, which it might not be able to get. It is not clear if this is a problem in practice, or what the best solution might be. So no attempt is made to address it. Reported-by: Tj Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1128861 Fixes: 4cc9b9f2bf4d ("nfsd: refine and rename NFSD_MAY_LOCK") Reviewed-by: Jeff Layton Signed-off-by: NeilBrown Signed-off-by: Chuck Lever

lockd: Remove dead code from fs/lockd/xdr4.c

2026-03-30T01:25:09+00:00

Now that all NLMv4 server-side procedures use XDR encoder and decoder functions generated by xdrgen, the hand-written code in fs/lockd/xdr4.c is no longer needed. This file contained the original XDR processing logic that has been systematically replaced throughout this series. Remove the file and its Makefile reference to eliminate the dead code. The helper function nlm4svc_set_file_lock_range() is still needed by the generated code, so move it to xdr4.h as an inline function where it remains accessible. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Remove C macros that are no longer used

2026-03-30T01:25:09+00:00

The conversion of all NLMv4 procedures to xdrgen-generated XDR functions is complete. The hand-rolled XDR size calculation macros (Ck, No, St, Rg) and the nlm_void structure definition served only the older implementations and are now unused. Also removes NLMDBG_FACILITY, which was set to the client debug flag in server-side code but never referenced, and corrects a comment to specify "NLMv4 Server procedures". Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Add LOCKD_SHARE_SVID constant for DOS sharing mode

2026-03-30T01:25:09+00:00

Replace the magic value ~(u32)0 with a named constant. This value is used as a synthetic svid when looking up lockowners for DOS share operations, which have no real process ID associated with them. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Use xdrgen XDR functions for the NLMv4 FREE_ALL procedure

2026-03-30T01:25:09+00:00

With all other NLMv4 procedures now converted to xdrgen-generated XDR functions, the FREE_ALL procedure can be converted as well. This conversion allows the removal of nlm4svc_retrieve_args(), a 79-line helper function that was used only by FREE_ALL to retrieve client information from lockd's internal data structures. Replace the NLMPROC4_FREE_ALL entry in the nlm_procedures4 array with an entry that uses xdrgen-built XDR decoders and encoders. The procedure handler is updated to use the new wrapper structure (nlm4_notify_wrapper) and call nlm4svc_lookup_host() directly, eliminating the need for the now-removed helper function. The .pc_argzero field is set to zero because xdrgen decoders fully initialize all fields in argp->xdrgen, making the early defensive memset unnecessary. The remaining argp fields that fall outside the xdrgen structures are cleared explicitly as needed. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Use xdrgen XDR functions for the NLMv4 NM_LOCK procedure

2026-03-30T01:25:09+00:00

Now that nlm4svc_do_lock() has been introduced to handle both monitored and non-monitored lock requests, the NLMv4 NM_LOCK procedure can be converted to use xdrgen-generated XDR functions. This conversion allows the removal of __nlm4svc_proc_lock(), a helper function that was previously shared between the LOCK and NM_LOCK procedures. Replace the NLMPROC4_NM_LOCK entry in the nlm_procedures4 array with an entry that uses xdrgen-built XDR decoders and encoders. The procedure handler is updated to call nlm4svc_do_lock() directly and access arguments through the argp->xdrgen hierarchy. The .pc_argzero field is set to zero because xdrgen decoders fully initialize all fields in argp->xdrgen, making the early defensive memset unnecessary. The remaining argp fields that fall outside the xdrgen structures are cleared explicitly as needed. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Use xdrgen XDR functions for the NLMv4 UNSHARE procedure

2026-03-30T01:25:09+00:00

Now that the share helpers have been decoupled from the NLMv3-specific struct nlm_args and file_lock initialization has been hoisted into the procedure handler, the NLMv4 UNSHARE procedure can be converted to use xdrgen-generated XDR functions. Replace the NLMPROC4_UNSHARE entry in the nlm_procedures4 array with an entry that uses xdrgen-built XDR decoders and encoders. The procedure handler is updated to use the new wrapper structures (nlm4_shareargs_wrapper and nlm4_shareres_wrapper) and access arguments through the argp->xdrgen hierarchy. The .pc_argzero field is set to zero because xdrgen decoders fully initialize all fields in argp->xdrgen, making the early defensive memset unnecessary. The remaining argp fields that fall outside the xdrgen structures are cleared explicitly as needed. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Use xdrgen XDR functions for the NLMv4 SHARE procedure

2026-03-30T01:25:09+00:00

Now that the share helpers have been decoupled from the NLMv3-specific struct nlm_args and file_lock initialization has been hoisted into the procedure handler, the NLMv4 SHARE procedure can be converted to use xdrgen-generated XDR functions. Replace the NLMPROC4_SHARE entry in the nlm_procedures4 array with an entry that uses xdrgen-built XDR decoders and encoders. The procedure handler is updated to use the new wrapper structures (nlm4_shareargs_wrapper and nlm4_shareres_wrapper) and access arguments through the argp->xdrgen hierarchy. The .pc_argzero field is set to zero because xdrgen decoders fully initialize all fields in argp->xdrgen, making the early defensive memset unnecessary. The remaining argp fields that fall outside the xdrgen structures are cleared explicitly as needed. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Prepare share helpers for xdrgen conversion

2026-03-30T01:25:09+00:00

In order to convert the NLMv4 server-side XDR functions to use xdrgen, the internal share helpers need to be decoupled from the NLMv3-specific struct nlm_args. NLMv4 procedures will use different argument structures once they are converted. Refactor nlmsvc_share_file() and nlmsvc_unshare_file() to accept individual arguments (oh, access, mode) instead of the common struct nlm_args. This allows both protocol versions to call these helpers without forcing a common argument structure. While here, add kdoc comments to both functions and fix a comment typo in the unshare path. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

lockd: Hoist file_lock init out of nlm4svc_decode_shareargs()

2026-03-30T01:25:09+00:00

The xdrgen-generated XDR decoders cannot initialize the file_lock structure because it is an internal kernel type, not part of the wire protocol. To prepare for converting SHARE and UNSHARE procedures to use xdrgen, the file_lock initialization must be moved from nlm4svc_decode_shareargs() into the procedure handlers themselves. This change removes one more dependency on the "struct nlm_lock::fl" field in fs/lockd/xdr4.c, allowing the XDR decoder to focus solely on unmarshalling wire data. Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever