From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/12714 Path: news.gmane.org!.POSTED!not-for-mail From: "Siebenborn, Axel" Newsgroups: gmane.linux.lib.musl.general Subject: RE: [PATCH] dl_addr: compare addr with sym->st_size. Date: Fri, 13 Apr 2018 10:16:52 +0000 Message-ID: References: <6a42ca4b6c9b4ea08925e232d7b57667@sap.com> <20180410142312.GE3094@brightrain.aerifal.cx> <20180413010152.GS3094@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1523614503 24398 195.159.176.226 (13 Apr 2018 10:15:03 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 13 Apr 2018 10:15:03 +0000 (UTC) To: "musl@lists.openwall.com" Original-X-From: musl-return-12730-gllmg-musl=m.gmane.org@lists.openwall.com Fri Apr 13 12:14:59 2018 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1f6vjO-0006Bg-Kk for gllmg-musl@m.gmane.org; Fri, 13 Apr 2018 12:14:58 +0200 Original-Received: (qmail 15497 invoked by uid 550); 13 Apr 2018 10:17:05 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 15479 invoked from network); 13 Apr 2018 10:17:04 -0000 Thread-Topic: [musl] [PATCH] dl_addr: compare addr with sym->st_size. Thread-Index: AdPLTEBvr5Sbu89kTKWUonO61LEwTwFenFuAACg772AAUqdAAAAXbOFw In-Reply-To: <20180413010152.GS3094@brightrain.aerifal.cx> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.21.23.236] Xref: news.gmane.org gmane.linux.lib.musl.general:12714 Archived-At: > -----Original Message----- > From: Rich Felker [mailto:dalias@aerifal.cx] On Behalf Of Rich Felker > On Wed, Apr 11, 2018 at 08:07:38AM +0000, Siebenborn, Axel wrote: > > Hi, > > > -----Original Message----- > > > From: Rich Felker [mailto:dalias@aerifal.cx] On Behalf Of Rich Felker > > > Sent: Dienstag, 10. April 2018 16:23 > > > To: musl@lists.openwall.com > > > Subject: Re: [musl] [PATCH] dl_addr: compare addr with sym->st_size. > > > > > > On Tue, Apr 03, 2018 at 01:06:09PM +0000, Siebenborn, Axel wrote: > > > > Hi, > > > > this patch fixes a problem with dl_addr. > > > > > > > > We found symbols, in cases we should not find a symbol, since the > > > > comparison with sym->st_size is missing. > > > > > > This was intentional, as my understanding of the historical behavior > > > on other implementations was that it would do this. If that's > > > incorrect we should investigate and document (or find existing > > > documentation of) what they really do. > > I don't know how the historical behavior was. Maybe you could point me = to > > some resources. > > However, I found that st_size might be 0, if the symbol has no or an > unknown > > size. How about comparing st_size to zero? > > > > - if (symaddr > addr || symaddr < best) > > + if (symaddr > addr || ((sym->st_size !=3D 0) &&= ((void*) > ((uint8_t*) symaddr + sym->st_size) < addr)) || symaddr < best) >=20 > I think this should be <=3D not <. symaddr+sym->st_size is one past the > end of the object/function, not part of it. >=20 > Aside from that, a couple style issues. This line is very long (well > over 80) after the change, and in musl we generally don't use !=3D0 or > excessive parens. Changing those things would help the length too. > Should also be char * rather than uint8_t*. With these changes I think > it looks like: >=20 > if (symaddr > addr || (sym->st_size && ((void*)((char > *)symaddr + sym->st_size) < addr)) || symaddr < best) >=20 > which is still really long. We could eliminate all the cast mess by > changing the addresses all to uintptr_t, which really should be done > (as a separate patch) anyway, since relational operators on pointers > that don't point into the same arrays is UB. But it still leaves the > line well over 80 chars. If may be best to write it as: >=20 > if (symaddr > addr || symaddr < best > || (sym->st_size && symaddr+sym->st_size < > addr)) > continue; >=20 > or even (simple patch): >=20 > if (symaddr > addr || symaddr < best) > continue; > + if (sym->st_size && symaddr+sym->st_size < addr) > + continue; >=20 > I can handle the independent UB fix and reformatting if you like. Thanks, that would be nice! >=20 > > > > @@ -1967,13 +1967,16 @@ int dladdr(const void *addr, Dl_info *info) > > > > } > > > > } > > > > > > > > - if (!best) return 0; > > > > - > > > > - if (DL_FDPIC && (bestsym->st_info&0xf) =3D=3D STT_FUNC) > > > > - best =3D p->funcdescs + (bestsym - p->syms); > > > > - > > > > info->dli_fname =3D p->name; > > > > info->dli_fbase =3D p->map; > > > > + if (!best) { > > > > + info->dli_sname =3D 0; > > > > + info->dli_saddr =3D 0; > > > > + return 0 > > > > > > This is missing a ; so it seems you tested a slightly different patch= ..? > > Sorry, that's embarrassing. I slightly refactored after testing. > > This line should be: > > + return 1; >=20 > OK, that looks right. >=20 > Rich Thanks for looking at this and for considering the patch! Axel