From a4425a57c7ad127b30cdfe271c870d5c8ebcfad7 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Fri, 21 Feb 2020 19:22:41 +1030 Subject: [PATCH] Fuzzers whining about mach-o support It's very easy to make bfd/mach-o.c allocate huge amounts of memory with fuzzed binaries. This make it a little harder. The patch also fixes a number of places where an attempt to detect overflow of multiplication was done with code like if (x * 4 < x) /* overflow case */ That of course doesn't work. There are plenty of values of x that overflow x * 4 but (x * 4) mod 2^n is greater than x. For example with 16-bit types, 0x6000 * 4 = 0x18000 mod 2^16 = 0x8000. * mach-o.c (bfd_mach_o_canonicalize_relocs): Fix ineffective overflow check. (bfd_mach_o_canonicalize_reloc): Likewise. (bfd_mach_o_canonicalize_dynamic_reloc): Likewise. Sanity check counts and offsets against file size. (bfd_mach_o_build_dysymtab): Fix ineffective overflow check. (bfd_mach_o_mangle_sections): Remove unnecessary overflow check. (bfd_mach_o_read_symtab_symbols): Sanity check count and offset against file size. Delete symbol table error message. (bfd_mach_o_read_dysymtab): Sanity check counts and offsets against file size. (bfd_mach_o_read_symtab): Likewise. (bfd_mach_o_read_command): Pass file size. (bfd_mach_o_scan): Sanity check command count against file size. --- bfd/ChangeLog | 17 +++++++ bfd/mach-o.c | 136 ++++++++++++++++++++++++++++++++++++++------------ 2 files changed, 122 insertions(+), 31 deletions(-) diff --git a/bfd/ChangeLog b/bfd/ChangeLog index 0f9c3e51f32..4ee96e4abc3 100644 --- a/bfd/ChangeLog +++ b/bfd/ChangeLog @@ -1,3 +1,20 @@ +2020-02-21 Alan Modra + + * mach-o.c (bfd_mach_o_canonicalize_relocs): Fix ineffective + overflow check. + (bfd_mach_o_canonicalize_reloc): Likewise. + (bfd_mach_o_canonicalize_dynamic_reloc): Likewise. Sanity check + counts and offsets against file size. + (bfd_mach_o_build_dysymtab): Fix ineffective overflow check. + (bfd_mach_o_mangle_sections): Remove unnecessary overflow check. + (bfd_mach_o_read_symtab_symbols): Sanity check count and offset + against file size. Delete symbol table error message. + (bfd_mach_o_read_dysymtab): Sanity check counts and offsets + against file size. + (bfd_mach_o_read_symtab): Likewise. + (bfd_mach_o_read_command): Pass file size. + (bfd_mach_o_scan): Sanity check command count against file size. + 2020-02-21 Alan Modra PR 25569 diff --git a/bfd/mach-o.c b/bfd/mach-o.c index 887dfc76ce6..4b7be6eb4e1 100644 --- a/bfd/mach-o.c +++ b/bfd/mach-o.c @@ -1614,13 +1614,11 @@ bfd_mach_o_canonicalize_relocs (bfd *abfd, unsigned long filepos, bfd_mach_o_backend_data *bed = bfd_mach_o_get_backend_data (abfd); unsigned long i; struct mach_o_reloc_info_external *native_relocs = NULL; - bfd_size_type native_size; + size_t native_size; /* Allocate and read relocs. */ - native_size = count * BFD_MACH_O_RELENT_SIZE; - - /* PR 17512: file: 09477b57. */ - if (native_size < count) + if (_bfd_mul_overflow (count, BFD_MACH_O_RELENT_SIZE, &native_size)) + /* PR 17512: file: 09477b57. */ goto err; if (bfd_seek (abfd, filepos, SEEK_SET) != 0) @@ -1663,9 +1661,11 @@ bfd_mach_o_canonicalize_reloc (bfd *abfd, asection *asect, if (asect->relocation == NULL) { - if (asect->reloc_count * sizeof (arelent) < asect->reloc_count) + size_t amt; + + if (_bfd_mul_overflow (asect->reloc_count, sizeof (arelent), &amt)) return -1; - res = bfd_malloc (asect->reloc_count * sizeof (arelent)); + res = bfd_malloc (amt); if (res == NULL) return -1; @@ -1718,12 +1718,30 @@ bfd_mach_o_canonicalize_dynamic_reloc (bfd *abfd, arelent **rels, if (mdata->dyn_reloc_cache == NULL) { - if ((dysymtab->nextrel + dysymtab->nlocrel) * sizeof (arelent) - < (dysymtab->nextrel + dysymtab->nlocrel)) - return -1; + ufile_ptr filesize = bfd_get_file_size (abfd); + size_t amt; + + if (filesize != 0) + { + if (dysymtab->extreloff > filesize + || dysymtab->nextrel > ((filesize - dysymtab->extreloff) + / BFD_MACH_O_RELENT_SIZE) + || dysymtab->locreloff > filesize + || dysymtab->nlocrel > ((filesize - dysymtab->locreloff) + / BFD_MACH_O_RELENT_SIZE)) + { + bfd_set_error (bfd_error_file_truncated); + return -1; + } + } + if (_bfd_mul_overflow (dysymtab->nextrel + dysymtab->nlocrel, + sizeof (arelent), &amt)) + { + bfd_set_error (bfd_error_file_too_big); + return -1; + } - res = bfd_malloc ((dysymtab->nextrel + dysymtab->nlocrel) - * sizeof (arelent)); + res = bfd_malloc (amt); if (res == NULL) return -1; @@ -2165,14 +2183,15 @@ bfd_mach_o_build_dysymtab (bfd *abfd, bfd_mach_o_dysymtab_command *cmd) { unsigned i; unsigned n; + size_t amt; mdata->filelen = FILE_ALIGN (mdata->filelen, 2); cmd->indirectsymoff = mdata->filelen; - mdata->filelen += cmd->nindirectsyms * 4; - - if (cmd->nindirectsyms * 4 < cmd->nindirectsyms) + if (_bfd_mul_overflow (cmd->nindirectsyms, 4, &amt)) return FALSE; - cmd->indirect_syms = bfd_zalloc (abfd, cmd->nindirectsyms * 4); + mdata->filelen += amt; + + cmd->indirect_syms = bfd_zalloc (abfd, amt); if (cmd->indirect_syms == NULL) return FALSE; @@ -2571,11 +2590,7 @@ bfd_mach_o_mangle_sections (bfd *abfd, bfd_mach_o_data_struct *mdata) } mdata->nsects = nsect; - if (_bfd_mul_overflow (mdata->nsects, sizeof (bfd_mach_o_section *), &amt)) - { - bfd_set_error (bfd_error_no_memory); - return FALSE; - } + amt = mdata->nsects * sizeof (bfd_mach_o_section *); mdata->sections = bfd_alloc (abfd, amt); if (mdata->sections == NULL) return FALSE; @@ -3921,17 +3936,31 @@ bfd_mach_o_read_symtab_symbols (bfd *abfd) bfd_mach_o_symtab_command *sym = mdata->symtab; unsigned long i; size_t amt; + ufile_ptr filesize; - if (sym == NULL || sym->symbols) + if (sym == NULL || sym->nsyms == 0 || sym->symbols) /* Return now if there are no symbols or if already loaded. */ return TRUE; + filesize = bfd_get_file_size (abfd); + if (filesize != 0) + { + unsigned int wide = mach_o_wide_p (&mdata->header); + unsigned int symwidth + = wide ? BFD_MACH_O_NLIST_64_SIZE : BFD_MACH_O_NLIST_SIZE; + + if (sym->symoff > filesize + || sym->nsyms > (filesize - sym->symoff) / symwidth) + { + bfd_set_error (bfd_error_file_truncated); + sym->nsyms = 0; + return FALSE; + } + } if (_bfd_mul_overflow (sym->nsyms, sizeof (bfd_mach_o_asymbol), &amt) || (sym->symbols = bfd_alloc (abfd, amt)) == NULL) { bfd_set_error (bfd_error_no_memory); - _bfd_error_handler (_("bfd_mach_o_read_symtab_symbols: " - "unable to allocate memory for symbols")); sym->nsyms = 0; return FALSE; } @@ -4273,7 +4302,8 @@ bfd_mach_o_read_thread (bfd *abfd, bfd_mach_o_load_command *command) } static bfd_boolean -bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command) +bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command, + ufile_ptr filesize) { bfd_mach_o_dysymtab_command *cmd = &command->command.dysymtab; bfd_mach_o_data_struct *mdata = bfd_mach_o_get_data (abfd); @@ -4315,6 +4345,12 @@ bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command) unsigned int module_len = wide ? 56 : 52; size_t amt; + if (cmd->modtaboff > filesize + || cmd->nmodtab > (filesize - cmd->modtaboff) / module_len) + { + bfd_set_error (bfd_error_file_truncated); + return FALSE; + } if (_bfd_mul_overflow (cmd->nmodtab, sizeof (bfd_mach_o_dylib_module), &amt)) { @@ -4369,7 +4405,14 @@ bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command) { unsigned long i; size_t amt; + struct mach_o_dylib_table_of_contents_external raw; + if (cmd->tocoff > filesize + || cmd->ntoc > (filesize - cmd->tocoff) / sizeof (raw)) + { + bfd_set_error (bfd_error_file_truncated); + return FALSE; + } if (_bfd_mul_overflow (cmd->ntoc, sizeof (bfd_mach_o_dylib_table_of_content), &amt)) { @@ -4385,7 +4428,6 @@ bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command) for (i = 0; i < cmd->ntoc; i++) { - struct mach_o_dylib_table_of_contents_external raw; bfd_mach_o_dylib_table_of_content *toc = &cmd->dylib_toc[i]; if (bfd_bread (&raw, sizeof (raw), abfd) != sizeof (raw)) @@ -4401,6 +4443,12 @@ bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command) unsigned int i; size_t amt; + if (cmd->indirectsymoff > filesize + || cmd->nindirectsyms > (filesize - cmd->indirectsymoff) / 4) + { + bfd_set_error (bfd_error_file_truncated); + return FALSE; + } if (_bfd_mul_overflow (cmd->nindirectsyms, sizeof (unsigned int), &amt)) { bfd_set_error (bfd_error_file_too_big); @@ -4431,6 +4479,12 @@ bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command) unsigned int i; size_t amt; + if (cmd->extrefsymoff > filesize + || cmd->nextrefsyms > (filesize - cmd->extrefsymoff) / 4) + { + bfd_set_error (bfd_error_file_truncated); + return FALSE; + } if (_bfd_mul_overflow (cmd->nextrefsyms, sizeof (bfd_mach_o_dylib_reference), &amt)) { @@ -4476,7 +4530,8 @@ bfd_mach_o_read_dysymtab (bfd *abfd, bfd_mach_o_load_command *command) } static bfd_boolean -bfd_mach_o_read_symtab (bfd *abfd, bfd_mach_o_load_command *command) +bfd_mach_o_read_symtab (bfd *abfd, bfd_mach_o_load_command *command, + ufile_ptr filesize) { bfd_mach_o_symtab_command *symtab = &command->command.symtab; bfd_mach_o_data_struct *mdata = bfd_mach_o_get_data (abfd); @@ -4496,6 +4551,15 @@ bfd_mach_o_read_symtab (bfd *abfd, bfd_mach_o_load_command *command) symtab->symbols = NULL; symtab->strtab = NULL; + if (symtab->symoff > filesize + || symtab->nsyms > (filesize - symtab->symoff) / BFD_MACH_O_NLIST_SIZE + || symtab->stroff > filesize + || symtab->strsize > filesize - symtab->stroff) + { + bfd_set_error (bfd_error_file_truncated); + return FALSE; + } + if (symtab->nsyms != 0) abfd->flags |= HAS_SYMS; @@ -4853,7 +4917,8 @@ bfd_mach_o_read_segment_64 (bfd *abfd, bfd_mach_o_load_command *command) } static bfd_boolean -bfd_mach_o_read_command (bfd *abfd, bfd_mach_o_load_command *command) +bfd_mach_o_read_command (bfd *abfd, bfd_mach_o_load_command *command, + ufile_ptr filesize) { bfd_mach_o_data_struct *mdata = bfd_mach_o_get_data (abfd); struct mach_o_load_command_external raw; @@ -4882,7 +4947,7 @@ bfd_mach_o_read_command (bfd *abfd, bfd_mach_o_load_command *command) return FALSE; break; case BFD_MACH_O_LC_SYMTAB: - if (!bfd_mach_o_read_symtab (abfd, command)) + if (!bfd_mach_o_read_symtab (abfd, command, filesize)) return FALSE; break; case BFD_MACH_O_LC_SYMSEG: @@ -4931,7 +4996,7 @@ bfd_mach_o_read_command (bfd *abfd, bfd_mach_o_load_command *command) return FALSE; break; case BFD_MACH_O_LC_DYSYMTAB: - if (!bfd_mach_o_read_dysymtab (abfd, command)) + if (!bfd_mach_o_read_dysymtab (abfd, command, filesize)) return FALSE; break; case BFD_MACH_O_LC_PREBIND_CKSUM: @@ -5204,10 +5269,19 @@ bfd_mach_o_scan (bfd *abfd, { bfd_mach_o_load_command *cmd; size_t amt; + ufile_ptr filesize = bfd_get_file_size (abfd); + + if (filesize == 0) + filesize = (ufile_ptr) -1; mdata->first_command = NULL; mdata->last_command = NULL; + if (header->ncmds > (filesize - hdrsize) / BFD_MACH_O_LC_SIZE) + { + bfd_set_error (bfd_error_file_truncated); + return FALSE; + } if (_bfd_mul_overflow (header->ncmds, sizeof (bfd_mach_o_load_command), &amt)) { @@ -5232,7 +5306,7 @@ bfd_mach_o_scan (bfd *abfd, cur->offset = prev->offset + prev->len; } - if (!bfd_mach_o_read_command (abfd, cur)) + if (!bfd_mach_o_read_command (abfd, cur, filesize)) return FALSE; } } -- 2.30.2