From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 7814) id 4287C385C33A; Tue, 14 Jun 2022 20:07:29 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4287C385C33A Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Fangrui Song To: glibc-cvs@sourceware.org Subject: [glibc] elf: Refine direct extern access diagnostics to protected symbol X-Act-Checkin: glibc X-Git-Author: Fangrui Song X-Git-Refname: refs/heads/master X-Git-Oldrev: 876cdf517d1c464ce3d8f7eaf4199565e5592f16 X-Git-Newrev: 7374c02b683b7110b853a32496a619410364d70b Message-Id: <20220614200729.4287C385C33A@sourceware.org> Date: Tue, 14 Jun 2022 20:07:29 +0000 (GMT) X-BeenThere: glibc-cvs@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Glibc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Jun 2022 20:07:29 -0000 https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=7374c02b683b7110b853a32496a619410364d70b commit 7374c02b683b7110b853a32496a619410364d70b Author: Fangrui Song Date: Tue Jun 14 13:07:27 2022 -0700 elf: Refine direct extern access diagnostics to protected symbol Refine commit 349b0441dab375099b1d7f6909c1742286a67da9: 1. Copy relocations for extern protected data do not work properly, regardless whether GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS is used. It makes sense to produce a warning unconditionally. 2. Non-zero value of an undefined function symbol may break pointer equality, but may be benign in many cases (many programs don't take the address in the shared object then compare it with the address in the executable). Reword the diagnostic to be clearer. 3. Remove the unneeded condition !(undef_map->l_1_needed & GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS). If the executable does not not have GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS (can only occur in error cases), the diagnostic should be emitted as well. When the defining shared object has GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS, report an error to apply the intended enforcement. Diff: --- sysdeps/generic/dl-protected.h | 50 +++++++++++++++++++++++------------------- 1 file changed, 27 insertions(+), 23 deletions(-) diff --git a/sysdeps/generic/dl-protected.h b/sysdeps/generic/dl-protected.h index 88cb8ec917..38386b5200 100644 --- a/sysdeps/generic/dl-protected.h +++ b/sysdeps/generic/dl-protected.h @@ -26,29 +26,33 @@ _dl_check_protected_symbol (const char *undef_name, const struct link_map *map, int type_class) { - if (undef_map != NULL - && undef_map->l_type == lt_executable - && !(undef_map->l_1_needed - & GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS) - && (map->l_1_needed - & GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS)) - { - if ((type_class & ELF_RTYPE_CLASS_COPY)) - /* Disallow copy relocations in executable against protected - data symbols in a shared object which needs indirect external - access. */ - _dl_signal_error (0, map->l_name, undef_name, - N_("copy relocation against non-copyable protected symbol")); - else if (ref->st_value != 0 - && ref->st_shndx == SHN_UNDEF - && (type_class & ELF_RTYPE_CLASS_PLT)) - /* Disallow non-zero symbol values of undefined symbols in - executable, which are used as the function pointer, against - protected function symbols in a shared object with indirect - external access. */ - _dl_signal_error (0, map->l_name, undef_name, - N_("non-canonical reference to canonical protected function")); - } + if (undef_map == NULL || undef_map->l_type != lt_executable) + return; + + if (type_class & ELF_RTYPE_CLASS_COPY) + /* Disallow copy relocations in executable against protected + data symbols in a shared object which needs indirect external + access. */ + _dl_error_printf ("warning: copy relocation against non-copyable " + "protected symbol `%s' in `%s'\n", + undef_name, map->l_name); + else if ((type_class & ELF_RTYPE_CLASS_PLT) && ref->st_value != 0 + && ref->st_shndx == SHN_UNDEF) + /* Disallow non-zero symbol values of undefined symbols in + executable, which are used as the function pointer, against + protected function symbols in a shared object with indirect + external access. */ + _dl_error_printf ( + "warning: direct reference to " + "protected function `%s' in `%s' may break pointer equality\n", + undef_name, map->l_name); + else + return; + + if (map->l_1_needed & GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS) + _dl_signal_error ( + 0, map->l_name, undef_name, + N_ ("error due to GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS")); } #endif /* _DL_PROTECTED_H */