elf: Check for empty tokens before dynamic string token expansion [BZ #22625]
The fillin_rpath function in elf/dl-load.c loops over each RPATH or RUNPATH tokens and interprets empty tokens as the current directory ("./"). In practice the check for empty token is done *after* the dynamic string token expansion. The expansion process can return an empty string for the $ORIGIN token if __libc_enable_secure is set or if the path of the binary can not be determined (/proc not mounted). Fix that by moving the check for empty tokens before the dynamic string token expansion. In addition, check for NULL pointer or empty strings return by expand_dynamic_string_token. The above changes highlighted a bug in decompose_rpath, an empty array is represented by the first element being NULL at the fillin_rpath level, but by using a -1 pointer in decompose_rpath and other functions. Changelog: [BZ #22625] * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic string token expansion. Check for NULL pointer or empty string possibly returned by expand_dynamic_string_token. (decompose_rpath): Check for empty path after dynamic string token expansion.
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