bug: notmuch show --decrypt leads to SIGSEGV
Matt Armstrong
marmstrong at google.com
Tue Aug 15 10:37:31 PDT 2017
I've been able to diagnose a SIGSEGV, and I have a workaround that
satisfies me. I'm unsure how to fix it, so I'll describe the problem
and leave it at that.
Repro:
% notmuch --version
notmuch 0.25+22~g0967e46 (a recent git @HEAD)
% notmuch show --format=sexp --decrypt thread:000000000002ad2c
-> SIGSEGV
Workaround:
Don't pass --decrypt. In Emacs, configure notmuch-crypto-process-mime
to shut off crypto processing, or C-u before in notmuch-show before
viewing a problematic thread.
Diagnosis:
mime-node.c's _mime_node_create() can return NULL in various scenarios
yet few to none of its callers appear to handle it properly. In this
particular case, the NULL is returned here:
#if (GMIME_MAJOR_VERSION < 3)
if ((GMIME_IS_MULTIPART_ENCRYPTED (part) && node->ctx->crypto->decrypt)
|| (GMIME_IS_MULTIPART_SIGNED (part) && node->ctx->crypto->verify)) {
GMimeContentType *content_type = g_mime_object_get_content_type (part);
const char *protocol = g_mime_content_type_get_parameter (content_type, "protocol");
cryptoctx = notmuch_crypto_get_context (node->ctx->crypto, protocol);
if (!cryptoctx) {
return NULL;
}
}
#endif
Note above a missing call to talloc_free(node) before the return, which
suggests a kind of bit-rot has set in for the GMIME_MAJOR_VERSION<3
case? Anyway...
mime_node_child() calls _mime_node_create() and will SIGSEGV:
node = _mime_node_create (parent, sub);
if (child == parent->next_child && parent->next_part_num != -1) {
/* We're traversing in depth-first order. Record the child's
* depth-first numbering. */
node->part_num = parent->next_part_num;
node->next_part_num = node->part_num + 1;
If I address that by returning NULL from mime_node_child() when
_mime_node_create() does, then the problem cascades to callers. None of
the callers of mime_node_child() explicitly handle the NULL return case:
mime-node.c: mime_node_t *child = mime_node_child (node, i);
notmuch-show.c:571: format_part_text (ctx, sp, mime_node_child (node, i), indent, params);
notmuch-show.c:622: format_part_sprinter (ctx, sp, mime_node_child (node, 0), first, TRUE, include_html);
notmuch-show.c:724: format_part_sprinter (ctx, sp, mime_node_child (node, i), i == 0, TRUE, include_html);
..._mime_node_seek_dfs_walk will proceed to SIGSEGV, and so will
format_part_...().
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