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Message-Id: <CFT5E45O9EIZ.B4QEQ40XC711@mussels> Date: Thu, 18 Nov 2021 16:21:13 -0300 From: Érico Nogueira <ericonr@...root.org> To: <musl@...ts.openwall.com> Cc: <monk@...oiled.info> Subject: Re: $ORIGIN rpath expansion without /proc: code looks wrong On Wed Nov 17, 2021 at 5:01 PM -03, Jeffrey Walton wrote: > On Wed, Nov 17, 2021 at 12:09 PM Érico Nogueira <ericonr@...root.org> > wrote: > > > > On Wed Nov 17, 2021 at 11:04 AM -03, Alexander Sosedkin wrote: > > > ... > > > Could somebody take a look at this and double-check that > > > this codepath makes sense? > > > > It does, but it might not be as robust as you wish. fixup_rpath() treats > > the RPATH entry as a single string, and does all $ORIGIN substitutions > > in one go (what splits the string by ":" is open_path()). This means > > that the entire RPATH entry containing $ORIGIN will be ignored if > > /proc/self/exe can't be accessed, despite one or more of them not > > depending on $ORIGIN. > > This has come up before on the list. It is different behavior from > libc, and it may be CVE worthy if a down-level library is used when an > updated library is available but lost because the RPATH/RUNPATH is > discarded. I would file such a CVE on the distro packaging or system administration rather than musl. The binaries you need to run so /proc is mounted shouldn't be the sort that depend on dynamic RPATH using ${ORIGIN} (rather than a static one or no RPATH at all), and any security fix should be confirmed to actually work before being deployed... Furthermore, I don't think an unprivileged user should be able to unmount /proc unless they have called prctl(PR_SET_NO_NEW_PRIVS, 1), no? Which would make any "attacks" be directed at themselves. > > Jeff
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