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List:       busybox
Subject:    Re: [PATCH] ed: don't use memcpy with overlapping memory regions
From:       Sören Tempel <soeren () soeren-tempel ! net>
Date:       2022-08-03 6:30:26
Message-ID: 34KG665IX3UJS.3FW56Z09RA3AK () 8pit ! net
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Pinging again as this is still unfixed and the proposed fix is rather trivial.

Sören Tempel <soeren@soeren-tempel.net> wrote:
> Ping.
> 
> soeren@soeren-tempel.net wrote:
> > From: Sören Tempel <soeren+git@soeren-tempel.net>
> > 
> > The memcpy invocations in the subCommand function, modified by this
> > commit, previously used memcpy with overlapping memory regions. This is
> > undefined behavior. On Alpine Linux, it causes BusyBox ed to crash since
> > we compile BusyBox with -D_FORTIFY_SOURCE=2 and our fortify-headers
> > implementation catches this source of undefined behavior [0]. The issue
> > can only be triggered if the replacement string is the same size or
> > shorter than the old string.
> > 
> > Looking at the code, it seems to me that a memmove(3) is what was
> > actually intended here, this commit modifies the code accordingly.
> > 
> > [0]: https://gitlab.alpinelinux.org/alpine/aports/-/issues/13504
> > ---
> >  editors/ed.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/editors/ed.c b/editors/ed.c
> > index 209ce9942..4a84f7433 100644
> > --- a/editors/ed.c
> > +++ b/editors/ed.c
> > @@ -720,7 +720,7 @@ static void subCommand(const char *cmd, int num1, int num2)
> >  		if (deltaLen <= 0) {
> >  			memcpy(&lp->data[offset], newStr, newLen);
> >  			if (deltaLen) {
> > -				memcpy(&lp->data[offset + newLen],
> > +				memmove(&lp->data[offset + newLen],
> >  					&lp->data[offset + oldLen],
> >  					lp->len - offset - oldLen);
> >  
> > _______________________________________________
> > busybox mailing list
> > busybox@busybox.net
> > http://lists.busybox.net/mailman/listinfo/busybox
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> busybox@busybox.net
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