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Fix CVE-2026-58013: GIOChannel memcmp buffer over-read

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Backport upstream fix for CVE-2026-58013 from MR !5170. The fix
prevents a memcmp() from reading past the end of the GString
buffer when using a multi-byte line terminator in GIOChannel.
The patch also includes a unit test for the fix. An additional
#include <stdint.h> was added to the test file to ensure
compatibility with glib 2.80.4 headers.

CVE: CVE-2026-58013
Upstream patches:
 - https://gitlab.gnome.org/GNOME/glib/-/merge_requests/5170.patch
Resolves: RHEL-212239

This commit was backported by Ymir, a Red Hat Enterprise Linux software maintenance AI agent.

Assisted-by: Ymir
This commit is contained in:
RHEL Packaging Agent 2026-08-20 12:43:04 +00:00
parent 168b5b6661
commit 5900a80b66
2 changed files with 131 additions and 0 deletions
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128
CVE-2026-58013.patch Normal file
View File

@ -0,0 +1,128 @@
From b440f8dc6d2764e95655fd2d384cbfecfab9f199 Mon Sep 17 00:00:00 2001
From: Philip Withnall <pwithnall@gnome.org>
Date: Tue, 28 Apr 2026 16:45:14 +0100
Subject: [PATCH] giochannel: Fix memcmp() off the end of the buffer with long
terminators
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
If the line terminator is longer than a single byte, and the current
line extends to the end of the buffer, and the buffer (which is a
`GString`) is near a power of two in length (as that’s how `GString`s
are allocated) it’s possible for the `memcmp()` which checks the
terminator to read off the end of the string buffer.
Fix that by checking the terminator length against the last character
before calling `memcmp()`. Add a unit test.
Spotted by linhlhq as #YWH-PGM9867-199. The fix is theirs (validated by
me), and the unit test is adapted from their proof of concept.
Signed-off-by: Philip Withnall <pwithnall@gnome.org>
Fixes: #3925
---
glib/giochannel.c | 3 +-
glib/tests/io-channel.c | 61 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 63 insertions(+), 1 deletion(-)
diff --git a/glib/giochannel.c b/glib/giochannel.c
index b44fff35b..4e682e2a9 100644
--- a/glib/giochannel.c
+++ b/glib/giochannel.c
@@ -1822,7 +1822,8 @@ read_again:
{
if (channel->line_term)
{
- if (memcmp (channel->line_term, nextchar, line_term_len) == 0)
+ if ((size_t) (lastchar - nextchar) >= line_term_len &&
+ memcmp (channel->line_term, nextchar, line_term_len) == 0)
{
line_length = nextchar - use_buf->str;
got_term_len = line_term_len;
diff --git a/glib/tests/io-channel.c b/glib/tests/io-channel.c
index c5dd01d04..4b4189b68 100644
--- a/glib/tests/io-channel.c
+++ b/glib/tests/io-channel.c
@@ -30,6 +30,7 @@
#include <glib.h>
#include <glib/gstdio.h>
+#include <stdint.h>
static void
test_small_writes (void)
@@ -216,6 +217,65 @@ test_read_line_embedded_nuls (void)
g_free (filename);
}
+static void
+test_read_line_long_terminator (void)
+{
+ uint8_t *test_data = NULL;
+ size_t test_data_len = 0;
+ int fd;
+ char *filename = NULL;
+ GIOChannel *channel = NULL;
+ GError *local_error = NULL;
+ char *line = NULL;
+ size_t line_length, terminator_pos;
+ const char *line_term;
+ int line_term_length;
+ GIOStatus status;
+
+ g_test_summary ("Test that reading a line when using a long terminator doesn’t over-read the buffer.");
+ g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/work_items/3925");
+
+ /* Write out a temporary file containing 2047 bytes. This is enough to make it
+ * near the length of the GString buffer when read back in. */
+ fd = g_file_open_tmp ("glib-test-io-channel-XXXXXX", &filename, &local_error);
+ g_assert_no_error (local_error);
+ g_close (g_steal_fd (&fd), NULL);
+
+ test_data_len = 2047;
+ test_data = g_malloc (test_data_len);
+ memset (test_data, 'M', test_data_len);
+ g_file_set_contents (filename, (const gchar *) test_data, test_data_len, &local_error);
+ g_assert_no_error (local_error);
+
+ /* Create the channel. */
+ channel = g_io_channel_new_file (filename, "r", &local_error);
+ g_assert_no_error (local_error);
+
+ /* Use a long line terminator so it could potentially over-read the end of the buffer. */
+ g_io_channel_set_line_term (channel, "DEADBEEF", 8);
+
+ line_term = g_io_channel_get_line_term (channel, &line_term_length);
+ g_assert_cmpstr (line_term, ==, "DEADBEEF");
+ g_assert_cmpint (line_term_length, ==, 8);
+
+ g_io_channel_set_encoding (channel, "UTF-8", &local_error);
+ g_assert_no_error (local_error);
+
+ status = g_io_channel_read_line (channel, &line, &line_length,
+ &terminator_pos, &local_error);
+ g_assert_no_error (local_error);
+ g_assert_cmpint (status, ==, G_IO_STATUS_NORMAL);
+ g_assert_cmpuint (line_length, ==, 2047);
+ g_assert_cmpuint (terminator_pos, ==, 2047);
+ g_assert_cmpmem (line, line_length, test_data, test_data_len);
+
+ g_free (line);
+ g_io_channel_unref (channel);
+ g_free (test_data);
+ g_unlink (filename);
+ g_free (filename);
+}
+
int
main (int argc,
char *argv[])
@@ -224,6 +284,7 @@ main (int argc,
g_test_add_func ("/io-channel/read-write", test_read_write);
g_test_add_func ("/io-channel/read-line/embedded-nuls", test_read_line_embedded_nuls);
+ g_test_add_func ("/io-channel/read-line/long-terminator", test_read_line_long_terminator);
return g_test_run ();
}

3
glib2.spec
View File

@ -56,6 +56,9 @@ Patch: gdbusnameowning-releasename-warning.patch
# https://gitlab.gnome.org/GNOME/glib/-/merge_requests/5156
Patch: CVE-2026-58016.patch
# https://gitlab.gnome.org/GNOME/glib/-/merge_requests/5170
Patch: CVE-2026-58013.patch
BuildRequires: gcc
BuildRequires: gcc-c++
BuildRequires: gettext