Re: [PATCH v3 2/3] 9p: skip directory entries with names longer than NAME_MAX

[Christian Schoenebeck <linux_oss@crudebyte.com>]

On Friday, 18 September 2026 04:48:50 CEST Haobin Wu wrote:
> The 9p wire format carries directory entry names of up to 65535 bytes
> and nothing on the client checks them against NAME_MAX. Since the
> previous patch, v9fs_dir_readdir_dotl() passes such names straight to
> dir_emit(), and the VFS only rejects names of PATH_MAX bytes or more in
> verify_dirent_name(), as -EIO, which again fails the whole getdents64()
> call.
> 
> A name between NAME_MAX and PATH_MAX is therefore returned to userspace
> even though every later operation on it fails with -ENAMETOOLONG, and
> POSIX requires readdir() to only return components of at most NAME_MAX
> bytes. Nothing can use such an entry, so skip it instead of returning it
> or failing the listing, reusing the strlen() result that was already
> computed for dir_emit(). Log the skipped entry at P9_DEBUG_ERROR, the
> same level as the strscpy() failure message this replaces.
> 
> Suggested-by: Dominique Martinet <asmadeus@codewreck.org>
> Link: https://lore.kernel.org/all/vz5bum547fqyxf5z4m3x7tuqkuq52jlopm65t7hvynqeulh7i3@2t4wnhfxs7qv/ 
> Signed-off-by: Haobin Wu <853555@gmail.com>

Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>

> ---
>  fs/9p/vfs_dir.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)