Re: [PATCH] arm64: idreg-override: Detect trailing "--" in __parse_cmdline()

[Catalin Marinas]

On Tue, Oct 27, 2026 at 03:49:45PM +0100, Thorsten Blum wrote:
> On Tue, Oct 27, 2026 at 12:14:07PM +0000, Catalin Marinas wrote:
> > On Thu, Oct 15, 2026 at 06:10:54PM +0200, Thorsten Blum wrote:
> > > __parse_cmdline() detects "--" only if it is followed by whitespace.
> > > However, at the end of the command line, it converts the dashes to
> > > underscores and tries to match "__" as an option.
> > > 
> > > Detect trailing "--" directly instead of converting it to "__".
> > > 
> > > Fixes: dc3f5aae0638 ("arm64: idreg-override: Avoid parameq() and parameqn()")
> > > Signed-off-by: Thorsten Blum <blum@xxxxxxxxxx>
> > > ---
> > >  arch/arm64/kernel/pi/idreg-override.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
> > > index acaf56234973..38aa28d19650 100644
> > > --- a/arch/arm64/kernel/pi/idreg-override.c
> > > +++ b/arch/arm64/kernel/pi/idreg-override.c
> > > @@ -352,8 +352,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
> > >  
> > >  		cmdline = skip_spaces(cmdline);
> > >  
> > > -		/* terminate on "--" appearing on the command line by itself */
> > > -		if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
> > > +		/* Stop at "--" appearing as a separate argument. */
> > > +		if (cmdline[0] == '-' && cmdline[1] == '-' &&
> > > +		    (!cmdline[2] || isspace(cmdline[2])))
> > >  			return;
> > 
> > I guess that's more of a cleanup. Does it actually fix anything to
> > deserve a Fixes tag? We skip an unnecessary lookup for "__" but there's
> > no functional difference.
> 
> Yes, it's a cleanup.
> 
> Functionally, the behavior is equivalent because it also happened to
> work before. However, commit dc3f5aae0638 removed the explicit detection
> of a trailing "--", so I added the Fixes tag mostly for provenance.

Makes sense. We might make it a comment when applying rather than a
dedicated Fixes tag.

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>