[PATCH v6 0/3] Fix opendir regression on some FS

[Adhemerval Zanella]

Some filesystem might return a non-representable d_off on getdents
call, even if there are few entries in the directories (for instance
ext4, which returns an internal FS hash).  This trigger issues with
non-LFS readdir when it finds the first non representable entry, and
also for LFS interface when used along with telldir (which return a
'long int', while d_off is potentially off64_t).

For instance, arm32 dirent and io tests running on qemu-user show the
following failures:

  FAIL: dirent/list
  FAIL: dirent/tst-scandir
  FAIL: io/tst-fts
  FAIL: io/tst-fts-lfs
  FAIL: io/tst-fts-time64

This patch changes non-LFS readdir so it clamps the d_off value if
it overflows.  It now uses getdents64 and maintains an internal map
between d_off that can not be represented by 'long int' (telldir
returned value).  seekdir will then set the correct offset by
using the input argument as a key to the internal list.

I have checked on x86_64-linux-gnu, i686-linux-gnu, and
arm-linux-gnueabihf.

Changes from v5:
  * Use non-LFS getdents logic on non-LFS readdir.
  * Clamp overflow d_off values.
  * Removed unrequired readdir64 refactor.

Changes from v4:
  * Allocate the telldir map an readdir, thus avoid telldir failure.
  * The translation buffer now uses a fixed size struct.
  * Fixed the condition to use the long to off64_t map.

Changes from v3:
  * Rebase against master.
  * Fixed a missing lock unlock on telldir.
  * Renamed tst-seekdir2 to tst-opendir-nolfs and check the opendir
    result against getdents64.


Adhemerval Zanella (3):
  linux: Use getdents64 on non-LFS readdir
  support: Add xreallocarray
  linux: Set internal DIR filepos as off64_t (BZ #23960, BZ #24050)

 include/dirent.h                            |   2 +-
 support/Makefile                            |   1 +
 support/support.h                           |   2 +
 support/xreallocarray.c                     |  29 ++++
 sysdeps/unix/sysv/linux/Makefile            |   2 +
 sysdeps/unix/sysv/linux/alpha/bits/dirent.h |   3 +
 sysdeps/unix/sysv/linux/bits/dirent.h       |   4 +
 sysdeps/unix/sysv/linux/closedir.c          |   4 +
 sysdeps/unix/sysv/linux/dirstream.h         |   9 +-
 sysdeps/unix/sysv/linux/opendir.c           |   3 +
 sysdeps/unix/sysv/linux/readdir.c           | 107 +++++++++++----
 sysdeps/unix/sysv/linux/readdir64.c         |  11 ++
 sysdeps/unix/sysv/linux/rewinddir.c         |   5 +
 sysdeps/unix/sysv/linux/seekdir.c           |  30 +++-
 sysdeps/unix/sysv/linux/telldir.c           |  36 +++++
 sysdeps/unix/sysv/linux/telldir.h           |  67 +++++++++
 sysdeps/unix/sysv/linux/tst-opendir-lfs.c   |   2 +
 sysdeps/unix/sysv/linux/tst-opendir.c       | 145 ++++++++++++++++++++
 18 files changed, 432 insertions(+), 30 deletions(-)
 create mode 100644 support/xreallocarray.c
 create mode 100644 sysdeps/unix/sysv/linux/telldir.h
 create mode 100644 sysdeps/unix/sysv/linux/tst-opendir-lfs.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-opendir.c

-- 
2.34.1