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elf: Remove fallback to the start of DT_STRTAB for dladdr

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When neither DT_HASH nor DT_GNU_HASH is present, the code scans
[DT_SYMTAB, DT_STRTAB). However, there is no guarantee that .dynstr
immediately follows .dynsym (e.g. lld typically places .gnu.version
after .dynsym).

In the absence of a hash table, symbol lookup will always fail
(map->l_nbuckets == 0 in dl-lookup.c) as if the object has no symbol, so
it seems fair for dladdr to do the same.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
Fangrui Song 2022-05-02 09:06:39 -07:00
parent 4e7e4f3b4b
commit 8e28aa3a51
1 changed files with 5 additions and 11 deletions
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16
elf/dl-addr.c
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@ -71,18 +71,10 @@ determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,
}
}
}
else
else if (match->l_info[DT_HASH] != NULL)
{
const ElfW(Sym) *symtabend;
if (match->l_info[DT_HASH] != NULL)
symtabend = (symtab
+ ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
else
/* There is no direct way to determine the number of symbols in the
dynamic symbol table and no hash table is present. The ELF
binary is ill-formed but what shall we do? Use the beginning of
the string table which generally follows the symbol table. */
symtabend = (const ElfW(Sym) *) strtab;
const ElfW (Sym) *symtabend
= (symtab + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
for (; (void *) symtab < (void *) symtabend; ++symtab)
if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
@ -96,6 +88,8 @@ determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,
&& symtab->st_name < strtabsize)
matchsym = (ElfW(Sym) *) symtab;
}
/* In the absence of a hash table, treat the object as if it has no symbol.
*/
if (mapp)
*mapp = match;