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author | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2020-12-30 21:52:38 +0000 |
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committer | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2021-04-12 14:33:02 +0100 |
commit | 3237824fb057632817a8de508d1fcb1f2e6f5c7e (patch) | |
tree | f1f46bb16fe1c9181696888caebf3f3e4eefc3cc | |
parent | 6b63f027658b2bbe41f2da374da0aff63a77647f (diff) | |
download | glibc-3237824fb057632817a8de508d1fcb1f2e6f5c7e.tar.gz glibc-3237824fb057632817a8de508d1fcb1f2e6f5c7e.tar.xz glibc-3237824fb057632817a8de508d1fcb1f2e6f5c7e.zip |
elf: Refactor _dl_update_slotinfo to avoid use after free
map is not valid to access here because it can be freed by a concurrent dlclose: during tls access (via __tls_get_addr) _dl_update_slotinfo is called without holding dlopen locks. So don't check the modid of map. The map == 0 and map != 0 code paths can be shared (avoiding the dtv resize in case of map == 0 is just an optimization: larger dtv than necessary would be fine too). -- v2: - commit message update
-rw-r--r-- | elf/dl-tls.c | 21 |
1 files changed, 5 insertions, 16 deletions
diff --git a/elf/dl-tls.c b/elf/dl-tls.c index 24d00c14ef..f8b32b3ecb 100644 --- a/elf/dl-tls.c +++ b/elf/dl-tls.c @@ -743,6 +743,8 @@ _dl_update_slotinfo (unsigned long int req_modid) { for (size_t cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt) { + size_t modid = total + cnt; + size_t gen = listp->slotinfo[cnt].gen; if (gen > new_gen) @@ -758,25 +760,12 @@ _dl_update_slotinfo (unsigned long int req_modid) /* If there is no map this means the entry is empty. */ struct link_map *map = listp->slotinfo[cnt].map; - if (map == NULL) - { - if (dtv[-1].counter >= total + cnt) - { - /* If this modid was used at some point the memory - might still be allocated. */ - free (dtv[total + cnt].pointer.to_free); - dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED; - dtv[total + cnt].pointer.to_free = NULL; - } - - continue; - } - /* Check whether the current dtv array is large enough. */ - size_t modid = map->l_tls_modid; - assert (total + cnt == modid); if (dtv[-1].counter < modid) { + if (map == NULL) + continue; + /* Resize the dtv. */ dtv = _dl_resize_dtv (dtv); |