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Message-ID: <4bf4f17b-f202-3166-9b76-59c9409d5223@infradead.org> Date: Thu, 14 Sep 2017 13:22:19 -0700 From: Randy Dunlap <rdunlap@...radead.org> To: Joe Lawrence <joe.lawrence@...hat.com>, mtk.manpages@...il.com Cc: lkml <linux-kernel@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, Alexander Viro <viro@...iv.linux.org.uk>, "Luis R. Rodriguez" <mcgrof@...nel.org>, Kees Cook <keescook@...omium.org>, Mikulas Patocka <mpatocka@...hat.com> Subject: Re: [PATCH RFC 0/3] A few round_pipe_size() and pipe-max-size fixups On 09/14/17 12:19, Joe Lawrence wrote: > On 09/14/2017 12:57 PM, Randy Dunlap wrote: >> On 09/14/17 06:26, Michael Kerrisk (man-pages) wrote: >>> Hello Joe, >>> >>> On 5 September 2017 at 16:44, Joe Lawrence <joe.lawrence@...hat.com> wrote: >>>> While backporting Michael's "pipe: fix limit handling" [1] patchset to a >>>> distro-kernel, Mikulas noticed that current upstream pipe limit handling >>>> contains a few problems: >>>> >>>> 1 - round_pipe_size() nr_pages overflow on 32bit: this would >>>> subsequently try roundup_pow_of_two(0), which is undefined. >> >> Hi, >> Sorry I missed the initial posting of this. >> >> The man page for F_SETPIPE_SZ (http://man7.org/linux/man-pages/man2/fcntl.2.html) >> says: >> "Attempts to set the pipe capacity below the page size are >> silently rounded up to the page size." >> >> That implies to me that setting pipe size to 0 would round up to PAGE_SIZE. >> Doesn't patch 1/3 change that to return -EINVAL? > > Good catch. How about something like this: > > /* > * Minimum pipe size, as required by POSIX > */ > unsigned int pipe_min_size = PAGE_SIZE; > > ... > > static inline unsigned int round_pipe_size(unsigned int size) > { > unsigned long nr_pages; > > + if (size < pipe_min_size) > + size = pipe_min_size; > + > nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; > if (nr_pages == 0) > return 0; > >> >> Otherwise all 3 patches look good to me. > > If the above is good, I can fold this into patch 1 and respin the set. Yes, looks good to me. Thanks. -- ~Randy
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