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elf: Fix DTV gap reuse logic (BZ #27135)

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This is updated version of the 572bd547d5 (reverted by 40ebfd016a)
that fixes the _dl_next_tls_modid issues.

This issue with 572bd547d5 patch is the DTV entry will be only
update on dl_open_worker() with the update_tls_slotinfo() call after
all dependencies are being processed by _dl_map_object_deps().  However
_dl_map_object_deps() itself might call _dl_next_tls_modid(), and since
the _dl_tls_dtv_slotinfo_list::map is not yet set the entry will be
wrongly reused.

This patch fixes by renaming the _dl_next_tls_modid() function to
_dl_assign_tls_modid() and by passing the link_map so it can set
the slotinfo value so a subsequente _dl_next_tls_modid() call will
see the entry as allocated.

The intermediary value is cleared up on remove_slotinfo() for the case
a library fails to load with RTLD_NOW.

This patch fixes BZ #27135.

Checked on x86_64-linux-gnu.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
This commit is contained in:
Adhemerval Zanella
2021-06-25 10:54:12 -03:00
parent 0e1f068108
commit ba33937be2
8 changed files with 349 additions and 33 deletions
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17
elf/dl-tls.c
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@@ -126,8 +126,8 @@ oom (void)
}
size_t
_dl_next_tls_modid (void)
void
_dl_assign_tls_modid (struct link_map *l)
{
size_t result;
@@ -157,7 +157,11 @@ _dl_next_tls_modid (void)
}
if (result - disp < runp->len)
break;
{
/* Mark the entry as used, so any dependency see it. */
atomic_store_relaxed (&runp->slotinfo[result - disp].map, l);
break;
}
disp += runp->len;
}
@@ -184,17 +188,14 @@ _dl_next_tls_modid (void)
atomic_store_relaxed (&GL(dl_tls_max_dtv_idx), result);
}
return result;
l->l_tls_modid = result;
}
size_t
_dl_count_modids (void)
{
/* It is rare that we have gaps; see elf/dl-open.c (_dl_open) where
we fail to load a module and unload it leaving a gap. If we don't
have gaps then the number of modids is the current maximum so
return that. */
/* The count is the max unless dlclose or failed dlopen created gaps. */
if (__glibc_likely (!GL(dl_tls_dtv_gaps)))
return GL(dl_tls_max_dtv_idx);