Re: [PATCH] Don't pre-create read-only files with --extract --xattrs

[Pavel Raiskup]

Gently ping on this.  This is easily reproducible, so I am re-attaching
the patch including a new test-case that fails with the current code:

    $ tar --xattrs -xf tar
    tar: setxattrat: Cannot set 'user.attr' extended attribute for file 'file': 
Permission denied
    tar: file: Cannot open: Permission denied
    tar: Exiting with failure status due to previous errors

Pavel

On Friday, October 9, 2020 1:39:11 PM CET Pavel Raiskup wrote:
> We used to respect the target file mode when pre-creating files in
> set_xattr, so we also pre-created read-only files that we were not able
> to open later for writing.  This is now fixed, and we always create the
> file with S_IWUSR.
> 
> Fixes the original bug report https://bugzilla.redhat.com/1886540
> 
> * src/extract.c (set_xattr): Blindly add S_IWUSR flag to pre-created
> files, to avoid openat failures later.
> ---
>  src/extract.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/src/extract.c b/src/extract.c
> index b73a591..2e650ad 100644
> --- a/src/extract.c
> +++ b/src/extract.c
> @@ -865,7 +865,13 @@ set_xattr (char const *file_name, struct tar_stat_info 
> const *st,
>  
>        for (;;)
>          {
> -          if (!mknodat (chdir_fd, file_name, mode ^ invert_permissions, 0))
> +          /* We'll open the file with O_WRONLY later by open_output_file,
> +             therefore we need to give us the S_IWUSR bit.  If the file was
> +             meant to be user-read-only, the permissions will be corrected by
> +             the set_stat call. */
> +          mode_t initial_mode = mode ^ invert_permissions | S_IWUSR;
> +
> +          if (!mknodat (chdir_fd, file_name, initial_mode, 0))
>              {
>                /* Successfully created file */
>                xattrs_xattrs_set (st, file_name, typeflag, 0);
>

0001-Don-t-pre-create-read-only-files-with-extract-xattrs.patch
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