| 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394959697 |
- From e11815bb7f0656f39e122073e0e3284ec7f5d021 Mon Sep 17 00:00:00 2001
- From: Mike Frysinger <vapier@gentoo.org>
- Date: Tue, 29 Mar 2016 23:35:44 -0400
- Subject: [PATCH] libsandbox: fix symtab walking with some ELFs
- MIME-Version: 1.0
- Content-Type: text/plain; charset=UTF-8
- Content-Transfer-Encoding: 8bit
- The strtab assumption works if there is no SysV hash table.
- Add logic to handle that scenario.
- URL: https://bugs.gentoo.org/578524
- Reported-by: Toralf Förster <toralf.foerster@gmx.de>
- Signed-off-by: Mike Frysinger <vapier@gentoo.org>
- ---
- libsandbox/wrapper-funcs/__wrapper_exec.c | 30 +++++++++++++++++-------------
- 1 file changed, 17 insertions(+), 13 deletions(-)
- diff --git a/libsandbox/wrapper-funcs/__wrapper_exec.c b/libsandbox/wrapper-funcs/__wrapper_exec.c
- index f7f51ab..d372366 100644
- --- a/libsandbox/wrapper-funcs/__wrapper_exec.c
- +++ b/libsandbox/wrapper-funcs/__wrapper_exec.c
- @@ -83,10 +83,10 @@ static bool sb_check_exec(const char *filename, char *const argv[])
- ({ \
- Elf##n##_Ehdr *ehdr = (void *)elf; \
- Elf##n##_Phdr *phdr = (void *)(elf + ehdr->e_phoff); \
- - Elf##n##_Addr vaddr, filesz, vsym = 0, vstr = 0; \
- - Elf##n##_Off offset, symoff = 0, stroff = 0; \
- + 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; \
- + Elf##n##_Sym *sym, *symend; \
- uint##n##_t ent_size = 0, str_size = 0; \
- bool dynamic = false; \
- size_t i; \
- @@ -106,6 +106,7 @@ static bool sb_check_exec(const char *filename, char *const argv[])
- case DT_SYMENT: ent_size = dyn->d_un.d_val; break; \
- case DT_STRTAB: vstr = dyn->d_un.d_val; break; \
- case DT_STRSZ: str_size = dyn->d_un.d_val; break; \
- + case DT_HASH: vhash = dyn->d_un.d_val; break; \
- } \
- ++dyn; \
- } \
- @@ -123,6 +124,8 @@ static bool sb_check_exec(const char *filename, char *const argv[])
- symoff = offset + (vsym - vaddr); \
- if (vstr >= vaddr && vstr < vaddr + filesz) \
- stroff = offset + (vstr - vaddr); \
- + if (vhash >= vaddr && vhash < vaddr + filesz) \
- + hashoff = offset + (vhash - vaddr); \
- } \
- \
- /* Finally walk the symbol table. This should generally be fast as \
- @@ -130,18 +133,20 @@ static bool sb_check_exec(const char *filename, char *const argv[])
- * out there do not export any symbols at all. \
- */ \
- if (symoff && stroff) { \
- - sym = (void *)(elf + symoff); \
- + /* 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: assume that the string \
- - * table always follows the symbol table. This seems like a poor \
- - * assumption to make, but glibc has gotten by this long. We could \
- - * rely on DT_HASH and walking all the buckets to find the largest \
- - * symbol index, but that's also a bit hacky. \
- + * 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. \
- * \
- * We don't sanity check the ranges here as you aren't executing \
- * corrupt programs in the sandbox. \
- */ \
- - for (i = 0; i < (vstr - vsym) / ent_size; ++i) { \
- + sym = (void *)(elf + symoff); \
- + symend = vhash ? (sym + hashes[1]) : (void *)(elf + stroff); \
- + while (sym < symend) { \
- char *symname = (void *)(elf + stroff + sym->st_name); \
- if (ELF##n##_ST_VISIBILITY(sym->st_other) == STV_DEFAULT && \
- sym->st_shndx != SHN_UNDEF && sym->st_shndx < SHN_LORESERVE && \
- @@ -149,9 +154,8 @@ static bool sb_check_exec(const char *filename, char *const argv[])
- /* Minor optimization to avoid strcmp. */ \
- symname[0] == '_' && symname[1] == '_') { \
- /* Blacklist internal C library symbols. */ \
- - size_t j; \
- - for (j = 0; j < ARRAY_SIZE(libc_alloc_syms); ++j) \
- - if (!strcmp(symname, libc_alloc_syms[j])) { \
- + for (i = 0; i < ARRAY_SIZE(libc_alloc_syms); ++i) \
- + if (!strcmp(symname, libc_alloc_syms[i])) { \
- run_in_process = false; \
- goto use_trace; \
- } \
- --
- 2.7.4
|
