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59 lines
1.9 KiB
59 lines
1.9 KiB
2 years ago
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commit c0669ae1a629e16b536bf11cdd0865e0dbcf4bee
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Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
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Date: Wed Dec 30 21:52:38 2020 +0000
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elf: Refactor _dl_update_slotinfo to avoid use after free
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map is not valid to access here because it can be freed by a concurrent
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dlclose: during tls access (via __tls_get_addr) _dl_update_slotinfo is
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called without holding dlopen locks. So don't check the modid of map.
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The map == 0 and map != 0 code paths can be shared (avoiding the dtv
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resize in case of map == 0 is just an optimization: larger dtv than
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necessary would be fine too).
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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diff --git a/elf/dl-tls.c b/elf/dl-tls.c
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index 9375650a3ab5247d..15ed01d795a8627a 100644
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--- a/elf/dl-tls.c
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+++ b/elf/dl-tls.c
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@@ -743,6 +743,8 @@ _dl_update_slotinfo (unsigned long int req_modid)
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{
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for (size_t cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
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{
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+ size_t modid = total + cnt;
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+
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size_t gen = listp->slotinfo[cnt].gen;
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if (gen > new_gen)
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@@ -758,25 +760,12 @@ _dl_update_slotinfo (unsigned long int req_modid)
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/* If there is no map this means the entry is empty. */
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struct link_map *map = listp->slotinfo[cnt].map;
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- if (map == NULL)
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- {
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- if (dtv[-1].counter >= total + cnt)
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- {
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- /* If this modid was used at some point the memory
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- might still be allocated. */
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- free (dtv[total + cnt].pointer.to_free);
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- dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED;
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- dtv[total + cnt].pointer.to_free = NULL;
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- }
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-
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- continue;
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- }
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-
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/* Check whether the current dtv array is large enough. */
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- size_t modid = map->l_tls_modid;
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- assert (total + cnt == modid);
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if (dtv[-1].counter < modid)
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{
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+ if (map == NULL)
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+ continue;
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+
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/* Resize the dtv. */
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dtv = _dl_resize_dtv (dtv);
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