From: Darrick J. Wong <djwong@xxxxxxxxxx>
As of 6.5-rc1, UBSAN trips over the ondisk extended attribute leaf block
definitions using an array length of 1 to pretend to be a flex array.
Kernel compilers have to support unbounded array declarations, so let's
correct this.
================================================================================
UBSAN: array-index-out-of-bounds in fs/xfs/libxfs/xfs_attr_leaf.c:2535:24
index 2 is out of range for type '__u8 [1]'
Call Trace:
<TASK>
dump_stack_lvl+0x33/0x50
__ubsan_handle_out_of_bounds+0x9c/0xd0
xfs_attr3_leaf_getvalue+0x2ce/0x2e0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
xfs_attr_leaf_get+0x148/0x1c0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
xfs_attr_get_ilocked+0xae/0x110 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
xfs_attr_get+0xee/0x150 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
xfs_xattr_get+0x7d/0xc0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
__vfs_getxattr+0xa3/0x100
vfs_getxattr+0x87/0x1d0
do_getxattr+0x17a/0x220
getxattr+0x89/0xf0
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_da_format.h | 73 +++++++++++++++++++++++++++++++++++++----
fs/xfs/xfs_ondisk.h | 4 +-
2 files changed, 67 insertions(+), 10 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_da_format.h b/fs/xfs/libxfs/xfs_da_format.h
index 25e2841084e1..b2362717c42e 100644
--- a/fs/xfs/libxfs/xfs_da_format.h
+++ b/fs/xfs/libxfs/xfs_da_format.h
@@ -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)
diff --git a/fs/xfs/xfs_ondisk.h b/fs/xfs/xfs_ondisk.h
index 9737b5a9f405..37be297f2532 100644
--- a/fs/xfs/xfs_ondisk.h
+++ b/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 +88,7 @@ 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);
