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x86_64: Avoid lazy relocation of tlsdesc [BZ #27137]

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Lazy tlsdesc relocation is racy because the static tls optimization and
tlsdesc management operations are done without holding the dlopen lock.

This similar to the commit b7cf203b5c
for aarch64, but it fixes a different race: bug 27137.

Another issue is that ld auditing ignores DT_BIND_NOW and thus tries to
relocate tlsdesc lazily, but that does not work in a BIND_NOW module
due to missing DT_TLSDESC_PLT. Unconditionally relocating tlsdesc at
load time fixes this bug 27721 too.
This commit is contained in:
Szabolcs Nagy 2021-02-11 11:29:23 +00:00
parent c0669ae1a6
commit 8f7e09f4db
1 changed files with 14 additions and 5 deletions
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19
sysdeps/x86_64/dl-machine.h
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@ -570,12 +570,21 @@ elf_machine_lazy_rel (struct link_map *map,
}
else if (__glibc_likely (r_type == R_X86_64_TLSDESC))
{
struct tlsdesc volatile * __attribute__((__unused__)) td =
(struct tlsdesc volatile *)reloc_addr;
const Elf_Symndx symndx = ELFW (R_SYM) (reloc->r_info);
const ElfW (Sym) *symtab = (const void *)D_PTR (map, l_info[DT_SYMTAB]);
const ElfW (Sym) *sym = &symtab[symndx];
const struct r_found_version *version = NULL;
td->arg = (void*)reloc;
td->entry = (void*)(D_PTR (map, l_info[ADDRIDX (DT_TLSDESC_PLT)])
+ map->l_addr);
if (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
{
const ElfW (Half) *vernum =
(const void *)D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
version = &map->l_versions[vernum[symndx] & 0x7fff];
}
/* Always initialize TLS descriptors completely at load time, in
case static TLS is allocated for it that requires locking. */
elf_machine_rela (map, reloc, sym, version, reloc_addr, skip_ifunc);
}
else if (__glibc_unlikely (r_type == R_X86_64_IRELATIVE))
{