According to the help for LDSO_PRELOAD_ENV_SUPPORT: "For set-user-ID/set-group-ID ELF binaries, only libraries in the standard search directories that are also set-user-ID will be loaded." However, this does not work. Looking at _dl_get_ready_to_run() in ldso/ldso/ldso.c it seems that LD_PRELOAD and _dl_preload is unset when _dl_secure is 1. This looks incorrect as _dl_load_elf_shared_library() in ldso/ldso/dl-elf.c seems to only allow loading of SUID libraries when _dl_secure is 1. Without having tested it, perhaps it would be enough to replace: _dl_preload = NULL; in ldso.c with: _dl_preload = _dl_getenv("LD_PRELOAD", envp); and moving the statement before the while that unsets unsecure envvars?
Created attachment 4364 [details] proposed patch to fix the issue. The attacched patch fix the issue spotted in this bug. There was also a discussion in stlinux bugzilla at https://bugzilla.stlinux.com/show_bug.cgi?id=19052, where show the tests done to fix it. Any comments are welcome. regards, Filippo Arcidiacono
The fix has been recently committed in uClibc master branch by Bernhard. Issue fixed.