Add NULL check in ns_lookup_list_search for DNS resolution#4844
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sumleo wants to merge 1 commit intobytecodealliance:mainfrom
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Add NULL check in ns_lookup_list_search for DNS resolution#4844sumleo wants to merge 1 commit intobytecodealliance:mainfrom
sumleo wants to merge 1 commit intobytecodealliance:mainfrom
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When no DNS allowlist is configured via --allow-resolve, wasi_ctx->ns_lookup_list is NULL. This NULL pointer gets passed to ns_lookup_list_search which dereferences it unconditionally at the while (*list) loop, causing a crash. A guest WASM module can trigger this by calling sock_addr_resolve.
sumleo
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TianlongLiang,
lum1n0us,
no1wudi and
yamt
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Summary
Fix a NULL pointer dereference in
ns_lookup_list_search()that causes a crash when no DNS allowlist is configured.Problem
When the WASI runtime is started without
--allow-resolve,wasi_ctx->ns_lookup_listis NULL. When a guest WASM module callssock_addr_resolve, the call chain eventually reachesns_lookup_list_search()inposix.c, which dereferences thelistparameter unconditionally atwhile (*list)(line 77). This causes a segmentation fault.Fix
Add a NULL check for the
listparameter before thewhile (*list)loop. Iflistis NULL (no DNS allowlist configured), the function returnsfalse, correctly denying the DNS lookup without crashing.Test
Verified that without
--allow-resolve, callingsock_addr_resolvefrom a WASM module no longer crashes the runtime and instead returns an appropriate error.