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elf: execve statically linked programs instead of crashing [BZ #28648]

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Programs without dynamic dependencies and without a program
interpreter are now run via execve.

Previously, the dynamic linker either crashed while attempting to
read a non-existing dynamic segment (looking for DT_AUDIT/DT_DEPAUDIT
data), or the self-relocated in the static PIE executable crashed
because the outer dynamic linker had already applied RELRO protection.

<dl-execve.h> is needed because execve is not available in the
dynamic loader on Hurd.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Florian Weimer
2021-12-05 11:28:34 +01:00
parent bada2e312a
commit c1cb2deeca
6 changed files with 161 additions and 8 deletions
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50
elf/rtld.c
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@@ -50,6 +50,7 @@
#include <gnu/lib-names.h>
#include <dl-tunables.h>
#include <get-dynamic-info.h>
#include <dl-execve.h>
#include <assert.h>
@@ -1106,6 +1107,45 @@ load_audit_modules (struct link_map *main_map, struct audit_list *audit_list)
}
}
/* Check if the executable is not actualy dynamically linked, and
invoke it directly in that case. */
static void
rtld_chain_load (struct link_map *main_map, char *argv0)
{
/* The dynamic loader run against itself. */
const char *rtld_soname
= ((const char *) D_PTR (&GL(dl_rtld_map), l_info[DT_STRTAB])
+ GL(dl_rtld_map).l_info[DT_SONAME]->d_un.d_val);
if (main_map->l_info[DT_SONAME] != NULL
&& strcmp (rtld_soname,
((const char *) D_PTR (main_map, l_info[DT_STRTAB])
+ main_map->l_info[DT_SONAME]->d_un.d_val)) == 0)
_dl_fatal_printf ("%s: loader cannot load itself\n", rtld_soname);
/* With DT_NEEDED dependencies, the executable is dynamically
linked. */
if (__glibc_unlikely (main_map->l_info[DT_NEEDED] != NULL))
return;
/* If the executable has program interpreter, it is dynamically
linked. */
for (size_t i = 0; i < main_map->l_phnum; ++i)
if (main_map->l_phdr[i].p_type == PT_INTERP)
return;
const char *pathname = _dl_argv[0];
if (argv0 != NULL)
_dl_argv[0] = argv0;
int errcode = __rtld_execve (pathname, _dl_argv, _environ);
const char *errname = strerrorname_np (errcode);
if (errname != NULL)
_dl_fatal_printf("%s: cannot execute %s: %s\n",
rtld_soname, pathname, errname);
else
_dl_fatal_printf("%s: cannot execute %s: %d\n",
rtld_soname, pathname, errno);
}
static void
dl_main (const ElfW(Phdr) *phdr,
ElfW(Word) phnum,
@@ -1374,14 +1414,8 @@ dl_main (const ElfW(Phdr) *phdr,
/* Now the map for the main executable is available. */
main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
if (__glibc_likely (state.mode == rtld_mode_normal)
&& GL(dl_rtld_map).l_info[DT_SONAME] != NULL
&& main_map->l_info[DT_SONAME] != NULL
&& strcmp ((const char *) D_PTR (&GL(dl_rtld_map), l_info[DT_STRTAB])
+ GL(dl_rtld_map).l_info[DT_SONAME]->d_un.d_val,
(const char *) D_PTR (main_map, l_info[DT_STRTAB])
+ main_map->l_info[DT_SONAME]->d_un.d_val) == 0)
_dl_fatal_printf ("loader cannot load itself\n");
if (__glibc_likely (state.mode == rtld_mode_normal))
rtld_chain_load (main_map, argv0);
phdr = main_map->l_phdr;
phnum = main_map->l_phnum;