Re: [PATCH 6/7] erofs: handle long xattr name prefixes properly

[Gao Xiang]

On 2023/4/7 22:17, Jingbo Xu wrote:

Make .{list,get}xattr routines adapted to long xattr name prefixes.
When the bit 7 of erofs_xattr_entry.e_name_index is set, it indicates
that it refers to a long xattr name prefix.

Signed-off-by: Jingbo Xu <jeffl...@linux.alibaba.com>
---
  fs/erofs/xattr.c | 60 +++++++++++++++++++++++++++++++++++++++++-------
  1 file changed, 52 insertions(+), 8 deletions(-)

diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
index 684571e83a2c..8d81593655e8 100644
--- a/fs/erofs/xattr.c
+++ b/fs/erofs/xattr.c
@@ -301,11 +301,39 @@ struct getxattr_iter {
        struct qstr name;
  };

+static int erofs_xattr_long_entrymatch(struct getxattr_iter *it,

+                                      struct erofs_xattr_entry *entry)
+{
+       struct erofs_sb_info *sbi = EROFS_SB(it->it.sb);
+       u8 idx = entry->e_name_index & EROFS_XATTR_LONG_PREFIX_MASK;
+       struct erofs_xattr_prefix_item *pf;
+
+       if (idx >= sbi->xattr_prefix_count)
+               return -ENOATTR;
+
+       pf = &sbi->xattr_prefixes[idx];

        struct erofs_xattr_prefix_item *pf = sbi->xattr_prefixes + idx;

        if (pf >= sbi->xattr_prefixes + sbi->xattr_prefix_count)
                return -ENOATTR;

?

+       if (it->index != pf->prefix->base_index)
+               return -ENOATTR;
+
+       if (strncmp(it->name.name, pf->prefix->infix, pf->infix_len))
+               return -ENOATTR;
+
+       it->name.name += pf->infix_len;
+       it->name.len -= pf->infix_len;
+       if (it->name.len != entry->e_name_len)
+               return -ENOATTR;
+       return 0;
+}
+
  static int xattr_entrymatch(struct xattr_iter *_it,
                            struct erofs_xattr_entry *entry)
  {
        struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);

+ /* should also match the infix for long name prefixes */

+       if (entry->e_name_index & EROFS_XATTR_LONG_PREFIX)
+               return erofs_xattr_long_entrymatch(it, entry);
+
        return (it->index != entry->e_name_index ||
                it->name.len != entry->e_name_len) ? -ENOATTR : 0;
  }
@@ -487,12 +515,26 @@ static int xattr_entrylist(struct xattr_iter *_it,
  {
        struct listxattr_iter *it =
                container_of(_it, struct listxattr_iter, it);
-       unsigned int prefix_len;
-       const char *prefix;
-
-       const struct xattr_handler *h =
-               erofs_xattr_handler(entry->e_name_index);
+       unsigned int base_index = entry->e_name_index;
+       unsigned int prefix_len, infix_len = 0;
+       const char *prefix, *infix = NULL;
+       const struct xattr_handler *h;
+
+       if (entry->e_name_index & EROFS_XATTR_LONG_PREFIX) {
+               struct erofs_sb_info *sbi = EROFS_SB(_it->sb);
+               u8 idx = entry->e_name_index & EROFS_XATTR_LONG_PREFIX_MASK;
+               struct erofs_xattr_prefix_item *pf;
+
+               if (idx >= sbi->xattr_prefix_count)
+                       return 1;
+
+               pf = &sbi->xattr_prefixes[idx];

                struct erofs_xattr_prefix_item *pf = sbi->xattr_prefixes + idx;

                if (pf >= sbi->xattr_prefixes + sbi->xattr_prefix_count)
                        return 1;
?


Otherwise it looks good to me,
Reviewed-by: Gao Xiang <hsiang...@linux.alibaba.com>

Thanks,
Gao Xiang

+               infix = pf->prefix->infix;
+               infix_len = pf->infix_len;
+               base_index = pf->prefix->base_index;
+       }

+ h = erofs_xattr_handler(base_index);

        if (!h || (h->list && !h->list(it->dentry)))
                return 1;

@@ -500,16 +542,18 @@ static int xattr_entrylist(struct xattr_iter *_it,

        prefix_len = strlen(prefix);

if (!it->buffer) {

-               it->buffer_ofs += prefix_len + entry->e_name_len + 1;
+               it->buffer_ofs += prefix_len + infix_len +
+                                       entry->e_name_len + 1;
                return 1;
        }

- if (it->buffer_ofs + prefix_len

+       if (it->buffer_ofs + prefix_len + infix_len +
                + entry->e_name_len + 1 > it->buffer_size)
                return -ERANGE;

memcpy(it->buffer + it->buffer_ofs, prefix, prefix_len);

-       it->buffer_ofs += prefix_len;
+       memcpy(it->buffer + it->buffer_ofs + prefix_len, infix, infix_len);
+       it->buffer_ofs += prefix_len + infix_len;
        return 0;
  }