ad9522f451
Backport fix for CVE-2026-58010 from upstream commit
8338414f6560. The patch fixes an off-by-one error in
gvs_tuple_is_normal() in glib/gvariant-serialiser.c, changing
`offset > value.size` to `offset >= value.size`, preventing a
single byte out-of-bounds read when checking a GVariant for
normal form. Includes a regression test adapted for the
glib2 2.56.4 API.
CVE: CVE-2026-58010
Upstream patches:
- 8338414f65.patch
Resolves: RHEL-212168
This commit was backported by Ymir, a Red Hat Enterprise Linux software maintenance AI agent.
Assisted-by: Ymir
100 lines
3.6 KiB
Diff
100 lines
3.6 KiB
Diff
From 1e659071a5138209dfefc647eebccbca43250434 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 | 41 ++++++++++++++++++++++++++++++++++++++
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2 files changed, 42 insertions(+), 1 deletion(-)
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diff --git a/glib/gvariant-serialiser.c b/glib/gvariant-serialiser.c
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index c6e400b53..9e862e50b 100644
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--- a/glib/gvariant-serialiser.c
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+++ b/glib/gvariant-serialiser.c
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@@ -1078,7 +1078,7 @@ 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 c4a996c1f..4d3186e46 100644
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--- a/glib/tests/gvariant.c
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+++ b/glib/tests/gvariant.c
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@@ -4842,6 +4842,45 @@ test_normal_checking_tuple_offsets (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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+
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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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+ g_bytes_unref (bytes);
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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 empty object path is normalised successfully to the base object
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* path, ‘/’. */
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static void
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@@ -4941,6 +4980,8 @@ main (int argc, char **argv)
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test_normal_checking_array_offsets);
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g_test_add_func ("/gvariant/normal-checking/tuple-offsets",
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test_normal_checking_tuple_offsets);
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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/empty-object-path",
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test_normal_checking_empty_object_path);
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