From dfd500d89545a1c23554e9d9d62d112c44b4c82e Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Tue, 4 Feb 2025 13:33:36 +1030 Subject: fs: nfs: acl: Avoid -Wflex-array-member-not-at-end warning -Wflex-array-member-not-at-end was introduced in GCC-14, and we are getting ready to enable it, globally. So, in order to avoid ending up with a flexible-array member in the middle of other structs, we use the `struct_group_tagged()` helper to create a new tagged `struct posix_acl_hdr`. This structure groups together all the members of the flexible `struct posix_acl` except the flexible array. As a result, the array is effectively separated from the rest of the members without modifying the memory layout of the flexible structure. We then change the type of the middle struct member currently causing trouble from `struct posix_acl` to `struct posix_acl_hdr`. We also want to ensure that when new members need to be added to the flexible structure, they are always included within the newly created tagged struct. For this, we use `static_assert()`. This ensures that the memory layout for both the flexible structure and the new tagged struct is the same after any changes. This approach avoids having to implement `struct posix_acl_hdr` as a completely separate structure, thus preventing having to maintain two independent but basically identical structures, closing the door to potential bugs in the future. We also use `container_of()` whenever we need to retrieve a pointer to the flexible structure, through which we can access the flexible-array member, if necessary. So, with these changes, fix the following warning: fs/nfs_common/nfsacl.c:45:26: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] Signed-off-by: Gustavo A. R. Silva Acked-by: Anna Schumaker Acked-by: Jeff Layton Signed-off-by: Chuck Lever --- include/linux/posix_acl.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h index e2d47eb1a7f3..62d497763e25 100644 --- a/include/linux/posix_acl.h +++ b/include/linux/posix_acl.h @@ -27,11 +27,16 @@ struct posix_acl_entry { }; struct posix_acl { - refcount_t a_refcount; - unsigned int a_count; - struct rcu_head a_rcu; + /* New members MUST be added within the struct_group() macro below. */ + struct_group_tagged(posix_acl_hdr, hdr, + refcount_t a_refcount; + unsigned int a_count; + struct rcu_head a_rcu; + ); struct posix_acl_entry a_entries[] __counted_by(a_count); }; +static_assert(offsetof(struct posix_acl, a_entries) == sizeof(struct posix_acl_hdr), + "struct member likely outside of struct_group_tagged()"); #define FOREACH_ACL_ENTRY(pa, acl, pe) \ for(pa=(acl)->a_entries, pe=pa+(acl)->a_count; pa Date: Mon, 10 Feb 2025 11:25:53 -0500 Subject: nfsd: disallow file locking and delegations for NFSv4 reexport We do not and cannot support file locking with NFS reexport over NFSv4.x for the same reason we don't do it for NFSv3: NFS reexport server reboot cannot allow clients to recover locks because the source NFS server has not rebooted, and so it is not in grace. Since the source NFS server is not in grace, it cannot offer any guarantees that the file won't have been changed between the locks getting lost and any attempt to recover/reclaim them. The same applies to delegations and any associated locks, so disallow them too. Clients are no longer allowed to get file locks or delegations from a reexport server, any attempts will fail with operation not supported. Update the "Reboot recovery" section accordingly in Documentation/filesystems/nfs/reexport.rst Signed-off-by: Mike Snitzer Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever --- include/linux/exportfs.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h index a087606ace19..fc93f0abf513 100644 --- a/include/linux/exportfs.h +++ b/include/linux/exportfs.h @@ -279,10 +279,22 @@ struct export_operations { atomic attribute updates */ #define EXPORT_OP_FLUSH_ON_CLOSE (0x20) /* fs flushes file data on close */ -#define EXPORT_OP_ASYNC_LOCK (0x40) /* fs can do async lock request */ +#define EXPORT_OP_NOLOCKS (0x40) /* no file locking support */ unsigned long flags; }; +/** + * exportfs_cannot_lock() - check if export implements file locking + * @export_ops: the nfs export operations to check + * + * Returns true if the export does not support file locking. + */ +static inline bool +exportfs_cannot_lock(const struct export_operations *export_ops) +{ + return export_ops->flags & EXPORT_OP_NOLOCKS; +} + extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid, int *max_len, struct inode *parent, int flags); -- cgit v1.2.3