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That's because, to redirect that file to file descriptor 3 for reading, you need read permission on the file. In my system, for example, /bin/ping cannot be read as a normal user (permissions 4711) and I get that same error.

You'll have to find another binary that has the SUID bit set and is readable. For example, in my system /bin/mount does the job. Still, in the last step I get the same error as reported by several other users (Inconsistency detected...)

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There is also a method at the end of the mail (in the Notes section) that details a method of using a SUID binary that you don't have read access to.

TL;DR

1. cause STDERR to block

2. run the SUID binary in the background in a way that triggers ld to try to write to STDERR causing it to block.

3. Replace /tmp/exploit with your binary

4. eliminate the blocking condition on STDERR.

5. ld will continue on using the $ORIGIN value.

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