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

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

On 02/10/23 08:09, Adhemerval Zanella Netto wrote:
> 
> 
> On 01/09/23 09:26, 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.
> 
> Ping.

Ping (x2).

> 
>> ---
>>  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..707fb5960e 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))
>> +    {
>> +      __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>