| This patch get the symbol table size by visiting the ELF section header. |
| Previous it figures the symbol table size by assuming string table always |
| directly follows the symbol table, but this assumption does not hold for |
| LLD. |
| --- a/libsandbox/wrapper-funcs/__wrapper_exec.c |
| +++ b/libsandbox/wrapper-funcs/__wrapper_exec.c |
| @@ -83,11 +83,12 @@ static bool sb_check_exec(const char *fi |
| ({ \ |
| Elf##n##_Ehdr *ehdr = (void *)elf; \ |
| Elf##n##_Phdr *phdr = (void *)(elf + ehdr->e_phoff); \ |
| + Elf##n##_Shdr *shdr = (void *)(elf + ehdr->e_shoff); \ |
| Elf##n##_Addr vaddr, filesz, vsym = 0, vstr = 0, vhash = 0; \ |
| Elf##n##_Off offset, symoff = 0, stroff = 0, hashoff = 0; \ |
| Elf##n##_Dyn *dyn; \ |
| Elf##n##_Sym *sym, *symend; \ |
| - uint##n##_t ent_size = 0, str_size = 0; \ |
| + uint##n##_t ent_size = 0, str_size = 0, sym_table_size = 0; \ |
| bool dynamic = false; \ |
| size_t i; \ |
| \ |
| @@ -114,6 +115,13 @@ static bool sb_check_exec(const char *fi |
| } \ |
| } \ |
| \ |
| + for (i = 0; i < ehdr->e_shnum; ++i) { \ |
| + if (shdr[i].sh_type == SHT_DYNSYM) { \ |
| + sym_table_size = shdr[i].sh_size; \ |
| + break; \ |
| + } \ |
| + }\ |
| + \ |
| if (dynamic && vsym && ent_size && vstr && str_size) { \ |
| /* Figure out where in the file these tables live. */ \ |
| for (i = 0; i < ehdr->e_phnum; ++i) { \ |
| @@ -136,16 +144,13 @@ static bool sb_check_exec(const char *fi |
| /* Hash entries are always 32-bits. */ \ |
| uint32_t *hashes = (void *)(elf + hashoff); \ |
| /* Nowhere is the # of symbols recorded, or the size of the symbol \ |
| - * table. Instead, we do what glibc does: use the sysv hash table \ |
| - * if it exists, else assume that the string table always directly \ |
| - * follows the symbol table. This seems like a poor assumption to \ |
| - * make, but glibc has gotten by this long. \ |
| + * table. Get the symbol table size by accessing the section headers. \ |
| * \ |
| * We don't sanity check the ranges here as you aren't executing \ |
| * corrupt programs in the sandbox. \ |
| */ \ |
| sym = (void *)(elf + symoff); \ |
| - symend = vhash ? (sym + hashes[1]) : (void *)(elf + stroff); \ |
| + symend = vhash ? (sym + hashes[1]) : (void *)(elf + symoff + sym_table_size); \ |
| while (sym < symend) { \ |
| char *symname = (void *)(elf + stroff + sym->st_name); \ |
| if (ELF##n##_ST_VISIBILITY(sym->st_other) == STV_DEFAULT && \ |
