Re: Issue in man page PR_SET_MDWE.2const

[Catalin Marinas <catalin.marinas@arm.com>]

Hi Alejandro,

On Thu, Dec 25, 2025 at 09:54:46PM +0100, Alejandro Colomar wrote:
> 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?

Just to make sure I understand, do you want to change "mapping
protections" to "mapping" in the PR_MDWE_REFUSE_EXEC_GAIN description?
Fine by me but I would use "mappings" (plural) instead. It matches the
following sentence.

-- 
Catalin