b3d5305454
Backport fix for CVE-2026-58013 to glib2-2.56.4. The patch
fixes a buffer over-read in giochannel.c where memcmp()
could read past the end of the buffer when a multi-byte
line terminator is used and the line extends to the end of
the buffer. A bounds check is added before the memcmp()
call. A minimal test file (io-channel.c) is included,
adapted for 2.56.4 API compatibility.
CVE: CVE-2026-58013
Upstream patches:
- 9f557746c5.patch
Resolves: RHEL-212229
This commit was backported by Ymir, a Red Hat Enterprise Linux software maintenance AI agent.
Assisted-by: Ymir
128 lines
4.3 KiB
Diff
128 lines
4.3 KiB
Diff
From bb5c37897584ca09c583161f908046edc2ec9d85 Mon Sep 17 00:00:00 2001
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From: Philip Withnall <pwithnall@gnome.org>
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Date: Tue, 28 Apr 2026 16:45:14 +0100
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Subject: [PATCH] giochannel: Fix memcmp() off the end of the buffer with long
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terminators
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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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If the line terminator is longer than a single byte, and the current
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line extends to the end of the buffer, and the buffer (which is a
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`GString`) is near a power of two in length (as that’s how `GString`s
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are allocated) it’s possible for the `memcmp()` which checks the
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terminator to read off the end of the string buffer.
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Fix that by checking the terminator length against the last character
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before calling `memcmp()`. Add a unit test.
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Spotted by linhlhq as #YWH-PGM9867-199. The fix is theirs (validated by
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me), and the unit test is adapted from their proof of concept.
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Signed-off-by: Philip Withnall <pwithnall@gnome.org>
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Fixes: #3925
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---
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glib/giochannel.c | 3 +-
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glib/tests/io-channel.c | 78 +++++++++++++++++++++++++++++++++++++++++
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2 files changed, 80 insertions(+), 1 deletion(-)
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create mode 100644 glib/tests/io-channel.c
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diff --git a/glib/giochannel.c b/glib/giochannel.c
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index f01817a83..32a1550b7 100644
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--- a/glib/giochannel.c
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+++ b/glib/giochannel.c
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@@ -1807,7 +1807,8 @@ read_again:
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{
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if (channel->line_term)
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{
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- if (memcmp (channel->line_term, nextchar, line_term_len) == 0)
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+ if ((size_t) (lastchar - nextchar) >= line_term_len &&
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+ memcmp (channel->line_term, nextchar, line_term_len) == 0)
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{
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line_length = nextchar - use_buf->str;
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got_term_len = line_term_len;
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diff --git a/glib/tests/io-channel.c b/glib/tests/io-channel.c
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new file mode 100644
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index 000000000..447675ee8
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--- /dev/null
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+++ b/glib/tests/io-channel.c
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@@ -0,0 +1,78 @@
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+/* Test for CVE-2026-58013: memcmp() off the end of the buffer with long terminators
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+ *
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+ * Copyright © 2026 Philip Withnall
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+ *
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+ * SPDX-License-Identifier: LGPL-2.1-or-later
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+ */
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+
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+#include <glib.h>
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+#include <glib/gstdio.h>
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+#include <string.h>
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+
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+static void
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+test_read_line_long_terminator (void)
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+{
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+ guint8 *test_data = NULL;
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+ gsize test_data_len = 0;
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+ gint fd;
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+ gchar *filename = NULL;
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+ GIOChannel *channel = NULL;
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+ GError *local_error = NULL;
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+ gchar *line = NULL;
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+ gsize line_length, terminator_pos;
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+ const gchar *line_term;
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+ gint line_term_length;
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+ GIOStatus status;
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+
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+ /* Write out a temporary file containing 2047 bytes. This is enough to make it
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+ * near the length of the GString buffer when read back in. */
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+ fd = g_file_open_tmp ("glib-test-io-channel-XXXXXX", &filename, &local_error);
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+ g_assert_no_error (local_error);
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+ g_close (fd, NULL);
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+ fd = -1;
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+
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+ test_data_len = 2047;
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+ test_data = g_malloc (test_data_len);
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+ memset (test_data, 'M', test_data_len);
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+ g_file_set_contents (filename, (const gchar *) test_data, test_data_len, &local_error);
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+ g_assert_no_error (local_error);
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+
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+ /* Create the channel. */
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+ channel = g_io_channel_new_file (filename, "r", &local_error);
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+ g_assert_no_error (local_error);
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+
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+ /* Use a long line terminator so it could potentially over-read the end of the buffer. */
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+ g_io_channel_set_line_term (channel, "DEADBEEF", 8);
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+
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+ line_term = g_io_channel_get_line_term (channel, &line_term_length);
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+ g_assert_cmpstr (line_term, ==, "DEADBEEF");
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+ g_assert_cmpint (line_term_length, ==, 8);
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+
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+ g_io_channel_set_encoding (channel, "UTF-8", &local_error);
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+ g_assert_no_error (local_error);
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+
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+ status = g_io_channel_read_line (channel, &line, &line_length,
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+ &terminator_pos, &local_error);
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+ g_assert_no_error (local_error);
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+ g_assert_cmpint (status, ==, G_IO_STATUS_NORMAL);
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+ g_assert_cmpuint (line_length, ==, 2047);
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+ g_assert_cmpuint (terminator_pos, ==, 2047);
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+ g_assert_cmpmem (line, line_length, test_data, test_data_len);
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+
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+ g_free (line);
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+ g_io_channel_unref (channel);
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+ g_free (test_data);
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+ g_unlink (filename);
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+ g_free (filename);
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+}
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+
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+int
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+main (int argc,
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+ char *argv[])
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+{
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+ g_test_init (&argc, &argv, NULL);
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+
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+ g_test_add_func ("/io-channel/read-line/long-terminator", test_read_line_long_terminator);
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+
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+ return g_test_run ();
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+}
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