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[PATCH] mmap.2: mmap with address NULL and MAP_FIXED results in EPERM

Started byTheodore Dubois <tblodt@icloud.com>
First post2017-06-15 22:20 +0200
Last post2017-06-16 17:30 +0200
Articles 2 — 2 participants

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  [PATCH] mmap.2: mmap with address NULL and MAP_FIXED results in EPERM Theodore Dubois <tblodt@icloud.com> - 2017-06-15 22:20 +0200
    Re: [PATCH] mmap.2: mmap with address NULL and MAP_FIXED results in  EPERM Michal Hocko <mhocko@kernel.org> - 2017-06-16 17:30 +0200

#1667227 — [PATCH] mmap.2: mmap with address NULL and MAP_FIXED results in EPERM

FromTheodore Dubois <tblodt@icloud.com>
Date2017-06-15 22:20 +0200
Subject[PATCH] mmap.2: mmap with address NULL and MAP_FIXED results in EPERM
Message-ID<tSJpf-75B-5@gated-at.bofh.it>
This can be verified with a simple test program. I'm not sure if this is
a kernel bug or a documentation bug, though...
---
 man2/mmap.2 | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/man2/mmap.2 b/man2/mmap.2
index d1942b52a..58361c837 100644
--- a/man2/mmap.2
+++ b/man2/mmap.2
@@ -515,6 +515,13 @@ was mounted no-exec.
 .\" (Since 2.4.25 / 2.6.0.)
 .TP
 .B EPERM
+The
+.I addr
+argument is 0 and
+.B MAP_FIXED
+is specified.
+.TP
+.B EPERM
 The operation was prevented by a file seal; see
 .BR fcntl (2).
 .TP
-- 
2.13.1

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#1667829 — Re: [PATCH] mmap.2: mmap with address NULL and MAP_FIXED results in EPERM

FromMichal Hocko <mhocko@kernel.org>
Date2017-06-16 17:30 +0200
SubjectRe: [PATCH] mmap.2: mmap with address NULL and MAP_FIXED results in EPERM
Message-ID<tT1ma-1PG-5@gated-at.bofh.it>
In reply to#1667227
On Thu 15-06-17 12:09:01, Theodore Dubois wrote:
> This can be verified with a simple test program. I'm not sure if this is
> a kernel bug or a documentation bug, though...

THis is not a bug. You are not allowed to mmap anything below
/proc/sys/vm/mmap_min_addr. So your patch to update documentation would
have to mention this sysctl to be correct.

> ---
>  man2/mmap.2 | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/man2/mmap.2 b/man2/mmap.2
> index d1942b52a..58361c837 100644
> --- a/man2/mmap.2
> +++ b/man2/mmap.2
> @@ -515,6 +515,13 @@ was mounted no-exec.
>  .\" (Since 2.4.25 / 2.6.0.)
>  .TP
>  .B EPERM
> +The
> +.I addr
> +argument is 0 and
> +.B MAP_FIXED
> +is specified.
> +.TP
> +.B EPERM
>  The operation was prevented by a file seal; see
>  .BR fcntl (2).
>  .TP
> -- 
> 2.13.1

-- 
Michal Hocko
SUSE Labs

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