02c48c2acb
Backport upstream commit aa1cb87d56111ef989811e824f0ac77484cc997f
to fix CVE-2026-58010, an off-by-one error in
gvs_tuple_is_normal() in glib/gvariant-serialiser.c.
The bug allowed a single byte out-of-bounds read off the end
of a GVariant's backing byte array during normal form checking.
The fix changes `>` to `>=` in an offset bounds check, and a
regression test is included.
CVE: CVE-2026-58010
Upstream patches:
- aa1cb87d56.patch
Resolves: RHEL-212171
This commit was backported by Ymir, a Red Hat Enterprise Linux software maintenance AI agent.
Assisted-by: Ymir
107 lines
4.0 KiB
Diff
107 lines
4.0 KiB
Diff
From bd09007528034db12bdf625b72112cbbe747e7bd Mon Sep 17 00:00:00 2001
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From: Philip Withnall <pwithnall@gnome.org>
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Date: Sun, 29 Mar 2026 19:10:41 +0100
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Subject: [PATCH] gvariant: Fix an off-by-one error in an offset comparison
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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This allows a single byte out-of-bounds read off the end of the
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(potentially untrusted) byte array backing a `GVariant` when it’s
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being checked for normal form.
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I can’t see how this could practically be exploited, but it’s certainly
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a security bug as the `GVariant` normal form checking code is supposed
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to be robust to malicious inputs.
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Spotted by linhlhq as #YWH-PGM9867-190, and fix and reproducer provided
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by them too, thanks. Confirmed and turned into a unit test by me.
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Signed-off-by: Philip Withnall <pwithnall@gnome.org>
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Fixes: #3915
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---
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glib/gvariant-serialiser.c | 2 +-
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glib/tests/gvariant.c | 48 ++++++++++++++++++++++++++++++++++++++
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2 files changed, 49 insertions(+), 1 deletion(-)
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diff --git a/glib/gvariant-serialiser.c b/glib/gvariant-serialiser.c
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index 0c2b119bc..7746ec4d0 100644
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--- a/glib/gvariant-serialiser.c
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+++ b/glib/gvariant-serialiser.c
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@@ -1241,7 +1241,7 @@ gvs_tuple_is_normal (GVariantSerialised value)
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while (offset & alignment)
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{
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- if (offset > value.size || value.data[offset] != '\0')
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+ if (offset >= value.size || value.data[offset] != '\0')
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return FALSE;
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offset++;
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}
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diff --git a/glib/tests/gvariant.c b/glib/tests/gvariant.c
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index fa8b05a20..5546d72dc 100644
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--- a/glib/tests/gvariant.c
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+++ b/glib/tests/gvariant.c
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@@ -5517,6 +5517,52 @@ test_normal_checking_tuple_offsets5 (void)
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g_variant_unref (variant);
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}
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+/* This is a regression test that looping over the padding bytes in a short
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+ * (non-normal) tuple doesn’t overflow the input data.
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+ *
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+ * See https://gitlab.gnome.org/GNOME/glib/-/issues/3915 */
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+static void
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+test_normal_checking_tuple_offsets6 (void)
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+{
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+ /*
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+ * Type: (ynqiuxthdsog) — 12 members, first member 'y' (byte) has
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+ * alignment 0, second 'n' (int16) has alignment 1.
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+ * With 1 byte of data (0x28), after reading the first byte member,
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+ * offset=1, alignment check for 'n' requires offset to be even,
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+ * so the while loop checks value.data[1] — but size is only 1.
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+ *
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+ * Use heap allocation via GBytes so ASan reports heap-buffer-overflow.
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+ */
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+ guint8 *heap_data = NULL;
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+ GBytes *bytes = NULL;
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+ const GVariantType *data_type = G_VARIANT_TYPE ("(ynqiuxthdsog)");
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+ GVariant *variant = NULL;
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+ GVariant *normal_variant = NULL;
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+ GVariant *expected = NULL;
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+
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+ g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/3915");
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+
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+ heap_data = g_malloc (1);
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+ heap_data[0] = 0x28;
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+ bytes = g_bytes_new_take (heap_data, 1);
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+
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+ variant = g_variant_new_from_bytes (data_type, bytes, FALSE);
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+ g_assert_nonnull (variant);
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+
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+ g_assert_false (g_variant_is_normal_form (variant));
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+
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+ normal_variant = g_variant_get_normal_form (variant);
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+ g_assert_nonnull (normal_variant);
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+
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+ expected = g_variant_new_parsed ("(byte 0x28, int16 0, uint16 0, 0, uint32 0, int64 0, uint64 0, handle 0, 0.0, '', objectpath '/', signature '')");
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+ g_assert_cmpvariant (expected, variant);
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+ g_assert_cmpvariant (expected, normal_variant);
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+
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+ g_variant_unref (expected);
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+ g_variant_unref (normal_variant);
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+ g_variant_unref (variant);
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+}
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+
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/* Test that an otherwise-valid serialised GVariant is considered non-normal if
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* its offset table entries are too wide.
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*
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@@ -5769,6 +5815,8 @@ main (int argc, char **argv)
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test_normal_checking_tuple_offsets4);
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g_test_add_func ("/gvariant/normal-checking/tuple-offsets5",
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test_normal_checking_tuple_offsets5);
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+ g_test_add_func ("/gvariant/normal-checking/tuple-offsets6",
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+ test_normal_checking_tuple_offsets6);
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g_test_add_func ("/gvariant/normal-checking/tuple-offsets/minimal-sized",
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test_normal_checking_tuple_offsets_minimal_sized);
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g_test_add_func ("/gvariant/normal-checking/empty-object-path",
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