[PATCH v3 0/4] A few round_pipe_size() and pipe-max-size fixups

[Joe Lawrence]

While backporting Michael's "pipe: fix limit handling" patchset to a
distro-kernel, Mikulas noticed that current upstream pipe limit handling
contains a few problems:

  1 - procfs signed wrap: echo'ing a large number into
      /proc/sys/fs/pipe-max-size and then cat'ing it back out shows a
      negative value.

  2 - round_pipe_size() nr_pages overflow on 32bit:  this would
      subsequently try roundup_pow_of_two(0), which is undefined.

  3 - visible non-rounded pipe-max-size value: there is no mutual
      exclusion or protection between the time pipe_max_size is assigned
      a raw value from proc_dointvec_minmax() and when it is rounded.

  4 - unsigned long -> unsigned int conversion makes for potential odd
      return errors from do_proc_douintvec_minmax_conv() and
      do_proc_dopipe_max_size_conv().

This version underwent the same testing as v1:
https://marc.info/?l=linux-kernel&m=150643571406022&w=2

v1 (from rfc):

- Re-arrange patchset order, push smaller fixes to the front
- Add a check so that round_pipe_size(size < pipe_min_size) will round
  up to round_pipe_size(pipe_min_size) as per man page [RD]
- Add new procfs proc_dopipe_max_size() and helpers to consolidate user
  space read / type validation / rounding / assignment [MP]

v2:
 - Fix !CONFIG_PROC_SYSCTL build case [buildbots]

v3:
 - s/proc_dointvec_minmax/proc_dopipe_max_size/ in comment 
   preceding pipe_proc_fn()
 - Added a fourth patch to address -ERANGE vs. -EINVAL inconsistencies in
   do_proc_douintvec_minmax_conv() and do_proc_dopipe_max_size_conv().

Joe Lawrence (4):
  pipe: match pipe_max_size data type with procfs
  pipe: avoid round_pipe_size() nr_pages overflow on 32-bit
  pipe: add proc_dopipe_max_size() to safely assign pipe_max_size
  sysctl: check for UINT_MAX before unsigned int min/max

 fs/pipe.c                 | 23 ++++++++++---------
 include/linux/pipe_fs_i.h |  1 +
 include/linux/sysctl.h    |  3 +++
 kernel/sysctl.c           | 57 ++++++++++++++++++++++++++++++++++++++++++++---
 4 files changed, 70 insertions(+), 14 deletions(-)

-- 
1.8.3.1