Merge tag 'xfs-6.5-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull xfs fixes from Darrick Wong:
 "Flexarray declaration conversions.

  This probably should've been done with the merge window open, but I
  was not aware that the UBSAN knob would be getting turned up for 6.5,
  and the fstests failures due to the kernel warnings are getting in the
  way of testing.

  Summary:

   - Convert all the array[1] declarations into the accepted flex
     array[] declarations so that UBSAN and friends will not get
     confused"

* tag 'xfs-6.5-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: convert flex-array declarations in xfs attr shortform objects
  xfs: convert flex-array declarations in xfs attr leaf blocks
  xfs: convert flex-array declarations in struct xfs_attrlist*

Author: torvalds

fs/xfs/libxfs/xfs_da_format.h

@@ -591,7 +591,7 @@ struct xfs_attr_shortform {
 		uint8_t valuelen;	/* actual length of value (no NULL) */
 		uint8_t flags;	/* flags bits (see xfs_attr_leaf.h) */
 		uint8_t nameval[];	/* name & value bytes concatenated */
-	} list[1];			/* variable sized array */
+	} list[];			/* variable sized array */
 };
 
 typedef struct xfs_attr_leaf_map {	/* RLE map of free bytes */
@@ -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/libxfs/xfs_fs.h

@@ -592,12 +592,12 @@ typedef struct xfs_attrlist_cursor {
 struct xfs_attrlist {
 	__s32	al_count;	/* number of entries in attrlist */
 	__s32	al_more;	/* T/F: more attrs (do call again) */
-	__s32	al_offset[1];	/* byte offsets of attrs [var-sized] */
+	__s32	al_offset[];	/* byte offsets of attrs [var-sized] */
 };
 
 struct xfs_attrlist_ent {	/* data from attr_list() */
 	__u32	a_valuelen;	/* number bytes in value of attr */
-	char	a_name[1];	/* attr name (NULL terminated) */
+	char	a_name[];	/* attr name (NULL terminated) */
 };
 
 typedef struct xfs_fsop_attrlist_handlereq {

fs/xfs/xfs_ondisk.h

@@ -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 +88,8 @@ 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_STRUCT_SIZE(struct xfs_attr_shortform,	4);
 	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);