Re: Issue in man page PR_SET_MDWE.2const

[Alejandro Colomar <alx@kernel.org>]

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Hi Helge, Florent, Catalin,

On Wed, Dec 24, 2025 at 02:38:23PM +0000, Helge Kreutzmann wrote:
> Without further ado, the following was found:
> 
> Issue:     mapping protections → mapping ?
> 
> "New memory mapping protections can't be writable and executable.  Non-"
> "executable mappings can't become executable."

That text was added in

	commit 457ca4a9ae3eae9835a5c011851c4eb88b49d322
	Author: Florent Revest <revest@chromium.org>
	Date:   Wed Oct 11 13:47:44 2023 +0200

	    prctl.2: Document PR_SET_MDWE and PR_GET_MDWE
	    
	    Memory-Deny-Write-Execute is a W^X process control originally introduced
	    by Joey Gouly.  I'm the author of the PR_MDWE_NO_INHERIT flag.
	    
	    Signed-off-by: Florent Revest <revest@chromium.org>
	    Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
	    Signed-off-by: Alejandro Colomar <alx@kernel.org>

So let's ask the author and reviewer.  The manual page says:

	$ mansect DESCRIPTION man/man2const/PR_SET_MDWE.2const \
	| MANWIDTH=64 man /dev/stdin \
	| cat;
	PR_SET_MDWE(2const)                         PR_SET_MDWE(2const)

	DESCRIPTION
	     Set the calling process’ Memory‐Deny‐Write‐Execute protec‐
	     tion  mask.  Once protection bits are set, they can not be
	     changed.

	     mask must be a bit mask of:

	     PR_MDWE_REFUSE_EXEC_GAIN
		    New memory mapping protections  can’t  be  writable
		    and  executable.  Non‐executable mappings can’t be‐
		    come executable.

	     PR_MDWE_NO_INHERIT  (since Linux 6.6)
		    Do not propagate MDWE protection to child processes
		    on fork(2).   Setting  this  bit  requires  setting
		    PR_MDWE_REFUSE_EXEC_GAIN too.

	Linux man‐pages (unreleased) (date)         PR_SET_MDWE(2const)

Do you agree with the wording fix proposal?


Have a lovely night!
Alex

-- 
<https://www.alejandro-colomar.es>

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