xfs: convert flex-array declarations in xfs attr leaf blocks (a49bbce5) · Commits · EulixOS / Software / Kernel

fs/xfs/libxfs/xfs_da_format.h

+65 −8

Original line number	Diff line number	Diff line
		@@ -620,19 +620,29 @@ typedef struct xfs_attr_leaf_entry { /* sorted on key, not name */
		typedef struct xfs_attr_leaf_name_local {
		__be16 valuelen; /* number of bytes in value */
		__u8 namelen; /* length of name bytes */
		__u8 nameval[1]; /* name/value bytes */
		/*
		* In Linux 6.5 this flex array was converted from nameval[1] to
		* nameval[]. Be very careful here about extra padding at the end;
		* see xfs_attr_leaf_entsize_local() for details.
		*/
		__u8 nameval[]; /* name/value bytes */
		} xfs_attr_leaf_name_local_t;

		typedef struct xfs_attr_leaf_name_remote {
		__be32 valueblk; /* block number of value bytes */
		__be32 valuelen; /* number of bytes in value */
		__u8 namelen; /* length of name bytes */
		__u8 name[1]; /* name bytes */
		/*
		* In Linux 6.5 this flex array was converted from name[1] to name[].
		* Be very careful here about extra padding at the end; see
		* xfs_attr_leaf_entsize_remote() for details.
		*/
		__u8 name[]; /* name bytes */
		} xfs_attr_leaf_name_remote_t;

		typedef struct xfs_attr_leafblock {
		xfs_attr_leaf_hdr_t hdr; /* constant-structure header block */
		xfs_attr_leaf_entry_t entries[1]; /* sorted on key, not name */
		xfs_attr_leaf_entry_t entries[]; /* sorted on key, not name */
		/*
		* The rest of the block contains the following structures after the
		* leaf entries, growing from the bottom up. The variables are never
		@@ -664,7 +674,7 @@ struct xfs_attr3_leaf_hdr {

		struct xfs_attr3_leafblock {
		struct xfs_attr3_leaf_hdr hdr;
		struct xfs_attr_leaf_entry entries[1];
		struct xfs_attr_leaf_entry entries[];

		/*
		* The rest of the block contains the following structures after the
		@@ -747,14 +757,61 @@ xfs_attr3_leaf_name_local(xfs_attr_leafblock_t *leafp, int idx)
		*/
		static inline int xfs_attr_leaf_entsize_remote(int nlen)
		{
		return round_up(sizeof(struct xfs_attr_leaf_name_remote) - 1 +
		nlen, XFS_ATTR_LEAF_NAME_ALIGN);
		/*
		* Prior to Linux 6.5, struct xfs_attr_leaf_name_remote ended with
		* name[1], which was used as a flexarray. The layout of this struct
		* is 9 bytes of fixed-length fields followed by a __u8 flex array at
		* offset 9.
		*
		* On most architectures, struct xfs_attr_leaf_name_remote had two
		* bytes of implicit padding at the end of the struct to make the
		* struct length 12. After converting name[1] to name[], there are
		* three implicit padding bytes and the struct size remains 12.
		* However, there are compiler configurations that do not add implicit
		* padding at all (m68k) and have been broken for years.
		*
		* This entsize computation historically added (the xattr name length)
		* to (the padded struct length - 1) and rounded that sum up to the
		* nearest multiple of 4 (NAME_ALIGN). IOWs, round_up(11 + nlen, 4).
		* This is encoded in the ondisk format, so we cannot change this.
		*
		* Compute the entsize from offsetof of the flexarray and manually
		* adding bytes for the implicit padding.
		*/
		const size_t remotesize =
		offsetof(struct xfs_attr_leaf_name_remote, name) + 2;

		return round_up(remotesize + nlen, XFS_ATTR_LEAF_NAME_ALIGN);
		}

		static inline int xfs_attr_leaf_entsize_local(int nlen, int vlen)
		{
		return round_up(sizeof(struct xfs_attr_leaf_name_local) - 1 +
		nlen + vlen, XFS_ATTR_LEAF_NAME_ALIGN);
		/*
		* Prior to Linux 6.5, struct xfs_attr_leaf_name_local ended with
		* nameval[1], which was used as a flexarray. The layout of this
		* struct is 3 bytes of fixed-length fields followed by a __u8 flex
		* array at offset 3.
		*
		* struct xfs_attr_leaf_name_local had zero bytes of implicit padding
		* at the end of the struct to make the struct length 4. On most
		* architectures, after converting nameval[1] to nameval[], there is
		* one implicit padding byte and the struct size remains 4. However,
		* there are compiler configurations that do not add implicit padding
		* at all (m68k) and would break.
		*
		* This entsize computation historically added (the xattr name and
		* value length) to (the padded struct length - 1) and rounded that sum
		* up to the nearest multiple of 4 (NAME_ALIGN). IOWs, the formula is
		* round_up(3 + nlen + vlen, 4). This is encoded in the ondisk format,
		* so we cannot change this.
		*
		* Compute the entsize from offsetof of the flexarray and manually
		* adding bytes for the implicit padding.
		*/
		const size_t localsize =
		offsetof(struct xfs_attr_leaf_name_local, nameval);

		return round_up(localsize + nlen + vlen, XFS_ATTR_LEAF_NAME_ALIGN);
		}

		static inline int xfs_attr_leaf_entsize_local_max(int bsize)

fs/xfs/xfs_ondisk.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -56,7 +56,7 @@ xfs_check_ondisk_structs(void)

		/* dir/attr trees */
		XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_leaf_hdr, 80);
		XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_leafblock, 88);
		XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_leafblock, 80);
		XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_rmt_hdr, 56);
		XFS_CHECK_STRUCT_SIZE(struct xfs_da3_blkinfo, 56);
		XFS_CHECK_STRUCT_SIZE(struct xfs_da3_intnode, 64);
		@@ -88,7 +88,7 @@ xfs_check_ondisk_structs(void)
		XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, valuelen, 4);
		XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, namelen, 8);
		XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, name, 9);
		XFS_CHECK_STRUCT_SIZE(xfs_attr_leafblock_t, 40);
		XFS_CHECK_STRUCT_SIZE(xfs_attr_leafblock_t, 32);
		XFS_CHECK_OFFSET(struct xfs_attr_shortform, hdr.totsize, 0);
		XFS_CHECK_OFFSET(struct xfs_attr_shortform, hdr.count, 2);
		XFS_CHECK_OFFSET(struct xfs_attr_shortform, list[0].namelen, 4);