[PATCH 07/31] xfs: allow xattr matching on name and value for parent pointers

Darrick J. Wong
2024-04-16T01:27:52Z

If a file is hardlinked with the same name but from multiple parents,
the parent pointers will all have the same dirent name (== attr name)
but with different parent_ino/parent_gen values. To disambiguate, we
need to be able to match on both the attr name and the attr value. This
is in contrast to regular xattrs, which are matchtg edit
d only on name.

Therefore, plumb in the ability to match shortform and local attrs on
name and value in the XFS_ATTR_PARENT namespace. Parent pointer attr
values are never large enough to be stored in a remote attr, so we need
can reject these cases as corruption.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/libxfs/xfs_attr_leaf.c | 48 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index e54a8372a30a4..e81cd48eb0000 100644
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -514,12 +514,33 @@ static inline unsigned int xfs_attr_match_mask(const struct xfs_da_args *args)
return XFS_ATTR_NSP_ONDISK_MASK | XFS_ATTR_INCOMPLETE;
}

+static inline bool
+xfs_attr_parent_match(
+ const struct xfs_da_args *args,
+ const void *value,
+ unsigned int valuelen)
+{
+ ASSERT(args->value != NULL);
+
+ /* Parent pointers do not use remote values */
+ if (!value)
+ return false;
+
+ /* The only value we support is a parent rec. */
+ if (valuelen != sizeof(struct xfs_parent_rec))
+ return false;
+
+ return memcmp(args->value, value, valuelen) == 0;
+}
+
static bool
xfs_attr_match(
struct xfs_da_args *args,
unsigned int attr_flags,
const unsigned char *name,
- unsigned int namelen)
+ unsigned int namelen,
+ const void *value,
+ unsigned int valuelen)
{
unsigned int mask = xfs_attr_match_mask(args);

@@ -530,6 +551,9 @@ xfs_attr_match(
if (memcmp(args->name, name, namelen) != 0)
return false;

+ if (attr_flags & XFS_ATTR_PARENT)
+ return xfs_attr_parent_match(args, value, valuelen);
+
return true;
}

@@ -539,6 +563,13 @@ xfs_attr_copy_value(
unsigned char *value,
int valuelen)
{
+ /*
+ * Parent pointer lookups require the caller to specify the name and
+ * value, so don't copy anything.
+ */
+ if (args->attr_filter & XFS_ATTR_PARENT)
+ return 0;
+
/*
* No copy if all we have to do is get the length
*/
@@ -748,7 +779,8 @@ xfs_attr_sf_findname(
sfe < xfs_attr_sf_endptr(sf);
sfe = xfs_attr_sf_nextentry(sfe)) {
if (xfs_attr_match(args, sfe->flags, sfe->nameval,
- sfe->namelen))
+ sfe->namelen, &sfe->nameval[sfe->namelen],
+ sfe->valuelen))
return sfe;
}

@@ -2444,18 +2476,22 @@ xfs_attr3_leaf_lookup_int(
if (entry->flags & XFS_ATTR_LOCAL) {
name_loc = xfs_attr3_leaf_name_local(leaf, probe);
if (!xfs_attr_match(args, entry->flags,
- name_loc->nameval,
- name_loc->namelen))
+ name_loc->nameval, name_loc->namelen,
+ &name_loc->nameval[name_loc->namelen],
+ be16_to_cpu(name_loc->valuelen)))
continue;
args->index = probe;
return -EEXIST;
} else {
+ unsigned int valuelen;
+
name_rmt = xfs_attr3_leaf_name_remote(leaf, probe);
+ valuelen = be32_to_cpu(name_rmt->valuelen);
if (!xfs_attr_match(args, entry->flags, name_rmt->name,
- name_rmt->namelen))
+ name_rmt->namelen, NULL, valuelen))
continue;
args->index = probe;
- args->rmtvaluelen = be32_to_cpu(name_rmt->valuelen);
+ args->rmtvaluelen = valuelen;
args->rmtblkno = be32_to_cpu(name_rmt->valueblk);
args->rmtblkcnt = xfs_attr3_rmt_blocks(
args->dp->i_mount,