linux-kernel - Re: [PATCH v3 0/4] A few round_pipe

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Message-ID: <b2bdb51b-b383-582f-cec1-d818e416d437@redhat.com>
Date:   Mon, 16 Oct 2017 09:24:26 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 0/4] A few round_pipe_size() and pipe-max-size fixups

On 10/10/2017 02:04 PM, Joe Lawrence wrote:
> 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(-)
> 

Thanks for the reviews, now who do I need to bug to get this merged into
a tree?  :)

v1:
Reviewed-by: Michael Kerrisk <mtk.manpages@...il.com>
"Looks good" from Randy Dunlap <rdunlap@...radead.org>

v3:
Reviewed-by: Mikulas Patocka <mpatocka@...hat.com>

-- Joe