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gvariant: Propagate trust when getting a child of a serialised variant

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If a variant is trusted, that means all its children are trusted, so
ensure that their checked offsets are set as such.

This allows a lot of the offset table checks to be avoided when getting
children from trusted serialised tuples, which speeds things up.

No unit test is included because this is just a performance fix. If
there are other slownesses, or regressions, in serialised `GVariant`
performance, the fuzzing setup will catch them like it did this one.

This change does reduce the time to run the oss-fuzz reproducer from 80s
to about 0.7s on my machine.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Fixes: #2841
oss-fuzz#54314
This commit is contained in:
Philip Withnall 2022-12-15 16:49:28 +00:00
parent 78da5faccb
commit 21a204147b
1 changed files with 2 additions and 2 deletions
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4
glib/gvariant-core.c
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@ -1198,8 +1198,8 @@ g_variant_get_child_value (GVariant *value,
child->contents.serialised.bytes = child->contents.serialised.bytes =
g_bytes_ref (value->contents.serialised.bytes); g_bytes_ref (value->contents.serialised.bytes);
child->contents.serialised.data = s_child.data; child->contents.serialised.data = s_child.data;
child->contents.serialised.ordered_offsets_up_to = s_child.ordered_offsets_up_to; child->contents.serialised.ordered_offsets_up_to = (value->state & STATE_TRUSTED) ? G_MAXSIZE : s_child.ordered_offsets_up_to;
child->contents.serialised.checked_offsets_up_to = s_child.checked_offsets_up_to; child->contents.serialised.checked_offsets_up_to = (value->state & STATE_TRUSTED) ? G_MAXSIZE : s_child.checked_offsets_up_to;
return child; return child;
} }