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Remove all loaded objects if dlopen fails, ignoring NODELETE [BZ #20839]

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This introduces a “pending NODELETE” state in the link map, which is
flipped to the persistent NODELETE state late in dlopen, via
activate_nodelete.    During initial relocation, symbol binding
records pending NODELETE state only.  dlclose ignores pending NODELETE
state.  Taken together, this results that a partially completed dlopen
is rolled back completely because new NODELETE mappings are unloaded.

Tested on x86_64-linux-gnu and i386-linux-gnu.

Change-Id: Ib2a3d86af6f92d75baca65431d74783ee0dbc292
This commit is contained in:
Florian Weimer
2019-11-13 15:44:56 +01:00
parent a509eb117f
commit f63b73814f
10 changed files with 328 additions and 38 deletions
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82
elf/dl-open.c
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@ -424,6 +424,40 @@ TLS generation counter wrapped! Please report this."));
}
}
/* Mark the objects as NODELETE if required. This is delayed until
after dlopen failure is not possible, so that _dl_close can clean
up objects if necessary. */
static void
activate_nodelete (struct link_map *new, int mode)
{
if (mode & RTLD_NODELETE || new->l_nodelete == link_map_nodelete_pending)
{
if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
_dl_debug_printf ("activating NODELETE for %s [%lu]\n",
new->l_name, new->l_ns);
new->l_nodelete = link_map_nodelete_active;
}
for (unsigned int i = 0; i < new->l_searchlist.r_nlist; ++i)
{
struct link_map *imap = new->l_searchlist.r_list[i];
if (imap->l_nodelete == link_map_nodelete_pending)
{
if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
_dl_debug_printf ("activating NODELETE for %s [%lu]\n",
imap->l_name, imap->l_ns);
/* Only new objects should have set
link_map_nodelete_pending. Existing objects should not
have gained any new dependencies and therefore cannot
reach NODELETE status. */
assert (!imap->l_init_called || imap->l_type != lt_loaded);
imap->l_nodelete = link_map_nodelete_active;
}
}
}
/* struct dl_init_args and call_dl_init are used to call _dl_init with
exception handling disabled. */
struct dl_init_args
@ -493,12 +527,6 @@ dl_open_worker (void *a)
return;
}
/* Mark the object as not deletable if the RTLD_NODELETE flags was passed.
Do this early so that we don't skip marking the object if it was
already loaded. */
if (__glibc_unlikely (mode & RTLD_NODELETE))
new->l_flags_1 |= DF_1_NODELETE;
if (__glibc_unlikely (mode & __RTLD_SPROF))
/* This happens only if we load a DSO for 'sprof'. */
return;
@ -514,19 +542,37 @@ dl_open_worker (void *a)
_dl_debug_printf ("opening file=%s [%lu]; direct_opencount=%u\n\n",
new->l_name, new->l_ns, new->l_direct_opencount);
/* If the user requested the object to be in the global namespace
but it is not so far, add it now. */
/* If the user requested the object to be in the global
namespace but it is not so far, prepare to add it now. This
can raise an exception to do a malloc failure. */
if ((mode & RTLD_GLOBAL) && new->l_global == 0)
add_to_global_resize (new);
/* Mark the object as not deletable if the RTLD_NODELETE flags
was passed. */
if (__glibc_unlikely (mode & RTLD_NODELETE))
{
add_to_global_resize (new);
add_to_global_update (new);
if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES)
&& new->l_nodelete == link_map_nodelete_inactive)
_dl_debug_printf ("marking %s [%lu] as NODELETE\n",
new->l_name, new->l_ns);
new->l_nodelete = link_map_nodelete_active;
}
/* Finalize the addition to the global scope. */
if ((mode & RTLD_GLOBAL) && new->l_global == 0)
add_to_global_update (new);
assert (_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT);
return;
}
/* Schedule NODELETE marking for the directly loaded object if
requested. */
if (__glibc_unlikely (mode & RTLD_NODELETE))
new->l_nodelete = link_map_nodelete_pending;
/* Load that object's dependencies. */
_dl_map_object_deps (new, NULL, 0, 0,
mode & (__RTLD_DLOPEN | RTLD_DEEPBIND | __RTLD_AUDIT));
@ -601,6 +647,14 @@ dl_open_worker (void *a)
int relocation_in_progress = 0;
/* Perform relocation. This can trigger lazy binding in IFUNC
resolvers. For NODELETE mappings, these dependencies are not
recorded because the flag has not been applied to the newly
loaded objects. This means that upon dlopen failure, these
NODELETE objects can be unloaded despite existing references to
them. However, such relocation dependencies in IFUNC resolvers
are undefined anyway, so this is not a problem. */
for (unsigned int i = nmaps; i-- > 0; )
{
l = maps[i];
@ -630,7 +684,7 @@ dl_open_worker (void *a)
_dl_start_profile ();
/* Prevent unloading the object. */
GL(dl_profile_map)->l_flags_1 |= DF_1_NODELETE;
GL(dl_profile_map)->l_nodelete = link_map_nodelete_active;
}
}
else
@ -661,6 +715,8 @@ dl_open_worker (void *a)
All memory allocations for new objects must have happened
before. */
activate_nodelete (new, mode);
/* Second stage after resize_scopes: Actually perform the scope
update. After this, dlsym and lazy binding can bind to new
objects. */
@ -820,6 +876,10 @@ no more namespaces available for dlmopen()"));
GL(dl_tls_dtv_gaps) = true;
_dl_close_worker (args.map, true);
/* All link_map_nodelete_pending objects should have been
deleted at this point, which is why it is not necessary
to reset the flag here. */
}
assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);