Re: BUG: $ORIGIN does not seem to work

[Rich Felker <dalias@libc.org>]

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On Sun, Jan 28, 2018 at 01:54:25AM +0100, Szabolcs Nagy wrote:
> * Stefan Fröberg <stefan.froberg@petroprogram.com> [2018-01-28 00:07:33 +0200]:
> > strace ./x
> ...
> > open("/root/batman/lib/libcrypto.so.1.1", O_RDONLY|O_CLOEXEC) = 3
> ...
> > ldd x
> >     /lib/ld-musl-x86_64.so.1 (0x7f22efa03000)
> >     libcrypto.so.1.1 => /usr/lib/libcrypto.so.1.1 (0x7f22ef352000)
> >     libc.so => /lib/ld-musl-x86_64.so.1 (0x7f22efa03000)
> 
> this is a bug in musl ldd: if the executable
> path has no / then it assumes origin is /, try
> 
> ldd ./x
> 
> then origin is ./ so it works as expected.

Does the attached patch look ok?

Alternatively we could fix the assumed invariant that p->name always
contains a slash by having the loader code in __dls3 allocate a copy
of argv[0] with "./" prepended, but that's a heavier cost at runtime
and doesn't seem to have any practical advantages.

Rich

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diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 3380240..f507bc4 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -807,7 +807,12 @@ static int fixup_rpath(struct dso *p, char *buf, size_t buf_size)
 		origin = p->name;
 	}
 	t = strrchr(origin, '/');
-	l = t ? t-origin : 0;
+	if (t) {
+		l = t-origin;
+	} else {
+		origin = ".";
+		l = 1;
+	}
 	p->rpath = malloc(strlen(p->rpath_orig) + n*l + 1);
 	if (!p->rpath) return -1;