Bug #10776: Ruby Chooses Incorrect Load Path For rubygems.rb

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: 2.0.0p598
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[alexcoomans (Alex Coomans)]

Problem

I believe this problem affects version 1.9.3 and up based on a git blame, but I haven't actually checked them.

The following conditions need to all be met:

1. Ruby must be compiled without --enable-shared
2. argv[0] to ruby must simply be ruby

And either one of the following need to be met:

1. Your PATH path must include a directory that has a directory named ruby before where ruby is located
2. The ruby binary is located in a directory named ruby (or any set of subdirectories). Eg: /test/ruby/bin/ruby

When you then try and execute ruby, it detects the wrong ruby install directory and fails to correctly load rubygems.rb - an example strace:

open("/home/vagrant/compiled/lib/ruby/site_ruby/2.0.0/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/vagrant/compiled/lib/ruby/site_ruby/2.0.0/x86_64-linux/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/vagrant/compiled/lib/ruby/site_ruby/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/vagrant/compiled/lib/ruby/vendor_ruby/2.0.0/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/vagrant/compiled/lib/ruby/vendor_ruby/2.0.0/x86_64-linux/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/vagrant/compiled/lib/ruby/vendor_ruby/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/vagrant/compiled/lib/ruby/2.0.0/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/home/vagrant/compiled/lib/ruby/2.0.0/x86_64-linux/rubygems.rb", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
write(2, "<internal:gem_prelude>:1:in `req"..., 37<internal:gem_prelude>:1:in `require') = 37
write(2, ": ", 2: )                       = 2
write(2, "cannot load such file -- rubygem"..., 36cannot load such file -- rubygems.rb) = 36

(Notice it is looking in /home/vagrant/compiled/lib instead of /home/vagrant/compiled/ruby/lib)

Reproduction

$ LDFLAGS='-Wl,-rpath=\$$ORIGIN/../lib' ./configure --with-out-ext=tk --with-out-ext=tcl --disable-pthread --enable-load-relative --disable-install-doc --prefix=/home/vagrant/compiled/ruby
$ make
$ make test
$ make install

$ cd /home/vagrant/compiled
$ PATH=":/home/vagrant/appinstall/ruby/bin" ruby
<internal:gem_prelude>:1:in `require': cannot load such file -- rubygems.rb (LoadError)
	from <internal:gem_prelude>:1:in `<compiled>'

FYI this bug cannot be reproduced through GDB by looking directly at /home/vagrant/appinstall/ruby/bin/ruby because GDB forces argv[0] to be the full path. You'll need to either patch GDB or use the C program in the Ongoing Problem section to use GDB to debug.

Patch

The following patch fixes the 99% case:

diff --git a/dln_find.c b/dln_find.c
index 56a1981..74beddd 100644
--- a/dln_find.c
+++ b/dln_find.c
@@ -278,11 +278,10 @@ dln_find_1(const char *fname, const char *path, char *fbuf, size_t size,
        }
 #endif /* _WIN32 or __EMX__ */

-       if (stat(fbuf, &st) == 0) {
+       if (stat(fbuf, &st) == 0 && !S_ISDIR(st.st_mode)) {
            if (exe_flag == 0) return fbuf;
            /* looking for executable */
-           if (!S_ISDIR(st.st_mode) && eaccess(fbuf, X_OK) == 0)
-               return fbuf;
+           if (eaccess(fbuf, X_OK) == 0) return fbuf;
        }
       next:
        /* if not, and no other alternatives, life is bleak */

How? dln_find_file_r is called by ruby_init_loadpath_safe to locate where the ruby binary itself is located. However dln_find_file_r calls dln_find_1 which in turn can return a directory. This patch changes dln_find_1 to only ever return a file. I couldn't find a case of dln_find_file_r being expected to return a directory.

Ongoing Problem

As I mentioned, the patch only fixes the 99% case - the code inherently is broken by relying on path. Take for example this C program:

#include <unistd.h>

int main() {
  char *const argv[] = {"ruby", NULL};

  execve("/home/vagrant/compiled/ruby/bin/ruby", argv, NULL);
  return 0; // not reached
}

Compile and run it inside of /home/vagrant/compiled to reproduce.

It would probably be better to look at /proc/self/exe when possible, but that would be more of a serious change

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Feedback

Alex Coomans wrote:

The following conditions need to all be met:

1. Ruby must be compiled without --enable-shared
2. argv[0] to ruby must simply be ruby

And either one of the following need to be met:

1. Your PATH path must include a directory that has a directory named ruby before where ruby is located
2. The ruby binary is located in a directory named ruby (or any set of subdirectories). Eg: /test/ruby/bin/ruby

When you then try and execute ruby, it detects the wrong ruby install directory and fails to correctly load rubygems.rb - an example strace:

I can't reproduce it with the latest 2.2

$ ls ~/ruby
2.2.0
$ (PATH=$HOME exec -a ruby ./ruby/2.2.0/bin/ruby -ve 'p RbConfig::CONFIG["configure_args"]')
ruby 2.2.0p36 (2015-01-22 revision 49375) [x86_64-linux]
" '-C' '--enable-shared' '--enable-load-relative' '--prefix=/' '--with-destdir=$(HOME)/ruby/$(RUBY_PROGRAM_VERSION)' '--disable-install-doc' '--without-ext=*win32*'"

[nobu (Nobuyoshi Nakada)]

• Status changed from Feedback to Assigned
• Assignee set to usa (Usaku NAKAMURA)
• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN to 2.0.0: REQUIRED, 2.1: DONTNEED, 2.2: DONTNEED

It could reproduce only with 2.0, but not 2.1 or later.

$ (PATH=$HOME exec -a ruby ./ruby/2.0.0/bin/ruby -ve 'p RbConfig::CONFIG["configure_args"]')
ruby 2.0.0p617 (2015-01-22 revision 49382) [x86_64-linux]
<internal:gem_prelude>:1:in `require': cannot load such file -- rubygems.rb (LoadError)
	from <internal:gem_prelude>:1:in `<compiled>'

[nobu (Nobuyoshi Nakada)]

• Status changed from Assigned to Feedback
• Assignee deleted (usa (Usaku NAKAMURA))
• Priority changed from Normal to 3
• Backport changed from 2.0.0: REQUIRED, 2.1: DONTNEED, 2.2: DONTNEED to 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

Sorry, it was my configuration miss, --prefix=/ doesn't work for 2.0 and should be --prefix=/..
So I can't reproduce it totally.

[nobu (Nobuyoshi Nakada)]

It seems a very platform (OS, libc) dependent issue.

What's your OS, kernel version, and libc version?

[nobu (Nobuyoshi Nakada)]

Alex Coomans wrote:

1. Ruby must be compiled without --enable-shared

Sorry, I misread this "without" as "with".

[nobu (Nobuyoshi Nakada)]

• Status changed from Feedback to Closed
• % Done changed from 0 to 100

Applied in changeset r49391.

---

dln_find.c: regular files only

• dln_find.c (dln_find_1): search regular files only. based on
  the patch by Alex Coomans in [ruby-core:67766]. [Bug #10776]

[alexcoomans (Alex Coomans)]

Awesome, thank you for looking at this so quickly!