Date: Sat, 26 Sep 2020 11:09:52 +0200 From: Szabolcs Nagy <nsz@...t70.net> To: Fangrui Song <i@...kray.me> Cc: musl@...ts.openwall.com, Rich Felker <dalias@...c.org> Subject: Re: SIGSEGV with TEXTREL * Fangrui Song <i@...kray.me> [2020-09-25 21:14:18 -0700]: > On Fri, Sep 25, 2020 at 7:53 PM Dominic Chen <d.c.ddcc@...il.com> wrote: > > > > On 9/25/2020 6:46 PM, Rich Felker wrote: > > > > > > The right way to make this more friendly, I think, would be tracking > > > the writable mapping range for each DSO (technically this is > > > incomplete since it could be multiple ranges, but in that case we'd > > > just take the convex hull of them and accept false negatives because > > > anything else is almost surely too big a performance hit), and > > > erroring out before processing a relocation at an address that's not > > > writable for its DSO. This would also go part of the way towards > > > making it possible for ldd to process untrusted files. > > > > I agree that that seems to be a better solution, and it was also > > discussed in the previous mailing list thread. But my point is just that > > given how this issue has been reoccurring, I think it'd be useful to do > > something now (e.g. emit a non-fail warning if TEXTRELs are present), > > rather than deferring any changes. > > > > Thanks, > > > > Dominic > > binutils 2.35 can be configured with --enable-textrel-check=yes, and > Linux/x86 defaults to 'yes'. ld emits a warning upon a text > relocation: > > warning: creating DT_TEXTREL in a PIE > > (LLD always disallows text relocations by default (-z text). You need > -z notext to enable DF_TEXTREL and text relocations.) nice and gcc passes -z text for static pie code so that case should not end up with text rels.
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