lib-oauth2: jwt - Avoid use-after-realloc of jwt_node front pointer#289
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lib-oauth2: jwt - Avoid use-after-realloc of jwt_node front pointer#289rootvector2 wants to merge 1 commit into
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sirainen
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May 27, 2026
| /* Take a local copy: array_append_space() below grows the | ||
| nodes buffer, which may move it via realloc and leave any | ||
| pointer into the old slot dangling. */ | ||
| const struct jwt_node subroot = *array_front(&nodes); |
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This *array_front() won't compile with non-gcc/clang which don't have enough type checks. Also, I think this could be changed to a one line patch by just adding subroot = array_front(&nodes); after the root = array_append_space(&nodes);, right?
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Done. Switched to refreshing subroot after array_append_space() so it survives a possible realloc, instead of the local-copy approach.
oauth2_jwt_copy_fields() captures subroot from array_front(&nodes) then calls array_append_space(&nodes) inside the inner loop. When the append cannot extend the buffer in place it relocates it, so subroot aliases the previous slot and later subroot->prefix / subroot->array reads operate on the abandoned location. Refresh subroot after the append.
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sirainen
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May 28, 2026
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| if (!json_node_is_singular(jnode)) { | ||
| root = array_append_space(&nodes); | ||
| subroot = array_front(&nodes); |
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A small comment before this would be good to prevent someone accidentally optimizing away the assignment.
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oauth2_jwt_copy_fields() captures subroot from array_front(&nodes)
then calls array_append_space(&nodes) inside the inner loop. When the
append cannot extend the buffer in place it relocates it, so subroot
aliases the previous slot and later subroot->prefix / subroot->array
reads operate on the abandoned location. Copy the front node by value
before the append.