9p: skip intermediate directory entry name copy in p9dirent_read()

v9fs_dir_readdir_dotl() decodes each entry of a Rreaddir reply with
p9dirent_read(), which parses it through p9pdu_readf("Qqbs"). The 's'
conversion in p9pdu_vreadf() already allocates a NUL-terminated copy
of the name from the wire buffer; p9dirent_read() then strscpy()s that
copy into the fixed 256-byte p9_dirent::d_name and frees the original.

The wire format carries the name length in 16 bits, so a name longer
than 255 bytes is valid on the wire and may well be valid on the
server's filesystem, but it makes strscpy() return -E2BIG.
v9fs_dir_readdir_dotl() turns that into -EIO and aborts getdents64(),
so every entry after the long one disappears from the listing.

Drop the second copy: keep the string allocated by p9pdu_vreadf() in
p9_dirent and let v9fs_dir_readdir_dotl(), its only user, free it once
dir_emit() has consumed it. p9_dirent is a short-lived stack object, so
the string's lifetime does not change.

Note that the VFS only rejects names of PATH_MAX bytes or more in
verify_dirent_name(), so after this change a name between NAME_MAX and
PATH_MAX is returned by getdents64() even though any later lookup on it
fails with -ENAMETOOLONG. The next patch skips such entries.

Fixes: 7751bdb3a095 ("9p: readdir implementation for 9p2000.L")
Closes: https://github.com/microsoft/WSL/issues/41192
Signed-off-by: Haobin Wu <853555@gmail.com>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Message-ID: <20260918024851.51229-2-853555@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

0 files changed, 0 insertions, 0 deletions