Re: [PATCH v2] linux: Make fdopendir fail with O_PATH (BZ 30373)

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

Ping, also the correct bug it fixes is 30737.

On 10/08/23 10:54, Adhemerval Zanella wrote:
> It is not strictly required by the POSIX, since O_PATH is a Linux
> extension, but it is QoI to fail early instead of at readdir.  Also
> the check is free, since fdopendir already checks if the file
> descriptor is opened for read.
> 
> Checked on x86_64-linux-gnu.
> ---
>  sysdeps/unix/sysv/linux/Makefile              |  1 +
>  sysdeps/unix/sysv/linux/fdopendir.c           |  8 +++-
>  .../unix/sysv/linux/tst-fdopendir-o_path.c    | 48 +++++++++++++++++++
>  3 files changed, 56 insertions(+), 1 deletion(-)
>  create mode 100644 sysdeps/unix/sysv/linux/tst-fdopendir-o_path.c
> 
> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index be801e3be4..ec0ba3eb05 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -199,6 +199,7 @@ tests += \
>    tst-clone3 \
>    tst-epoll \
>    tst-fanotify \
> +  tst-fdopendir-o_path \
>    tst-getauxval \
>    tst-gettid \
>    tst-gettid-kill \
> diff --git a/sysdeps/unix/sysv/linux/fdopendir.c b/sysdeps/unix/sysv/linux/fdopendir.c
> index 861345396c..839690f4d3 100644
> --- a/sysdeps/unix/sysv/linux/fdopendir.c
> +++ b/sysdeps/unix/sysv/linux/fdopendir.c
> @@ -37,10 +37,16 @@ __fdopendir (int fd)
>        return NULL;
>      }
>  
> -  /* Make sure the descriptor allows for reading.  */
>    int flags = __fcntl64_nocancel (fd, F_GETFL);
>    if (__glibc_unlikely (flags == -1))
>      return NULL;
> +  /* Fail early for descriptors opened with O_PATH.  */
> +  if (__glibc_unlikely ((flags & O_PATH) == O_PATH))
> +    {
> +      __set_errno (EBADF);
> +      return NULL;
> +    }
> +  /* Make sure the descriptor allows for reading.  */
>    if (__glibc_unlikely ((flags & O_ACCMODE) == O_WRONLY))
>      {
>        __set_errno (EINVAL);
> diff --git a/sysdeps/unix/sysv/linux/tst-fdopendir-o_path.c b/sysdeps/unix/sysv/linux/tst-fdopendir-o_path.c
> new file mode 100644
> index 0000000000..2531cf8ddb
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-fdopendir-o_path.c
> @@ -0,0 +1,48 @@
> +/* Check if fdopendir fails with file descriptor opened with O_PATH (BZ 30737)
> +   Copyright (C) 2023 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <dirent.h>
> +#include <support/check.h>
> +#include <support/temp_file.h>
> +#include <support/xunistd.h>
> +
> +static int
> +do_test (void)
> +{
> +  char *dirname = support_create_temp_directory ("tst-fdopendir-o_path");
> +
> +  {
> +    int fd = xopen (dirname, O_RDONLY |  O_DIRECTORY, 0600);
> +    DIR *dir = fdopendir (fd);
> +    TEST_VERIFY_EXIT (dir != NULL);
> +    closedir (dir);
> +  }
> +
> +  {
> +    int fd = xopen (dirname, O_RDONLY | O_PATH | O_DIRECTORY, 0600);
> +    TEST_VERIFY (fdopendir (fd) == NULL);
> +    TEST_COMPARE (errno, EBADF);
> +    xclose (fd);
> +  }
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>