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From 23514c72b780f3da097ecf33a793b7ba9c2070d2 Mon Sep 17 00:00:00 2001
From: Arjun Shankar <arjun@redhat.com>
Date: Mon, 15 Jan 2024 17:44:43 +0100
Subject: [PATCH 1/3] syslog: Fix heap buffer overflow in __vsyslog_internal
(CVE-2023-6246)
__vsyslog_internal did not handle a case where printing a SYSLOG_HEADER
containing a long program name failed to update the required buffer
size, leading to the allocation and overflow of a too-small buffer on
the heap. This commit fixes that. It also adds a new regression test
that uses glibc.malloc.check.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
(cherry picked from commit 6bd0e4efcc78f3c0115e5ea9739a1642807450da)
---
misc/Makefile | 8 ++-
misc/syslog.c | 50 +++++++++++++------
misc/tst-syslog-long-progname.c | 39 +++++++++++++++
.../postclean.req | 0
4 files changed, 82 insertions(+), 15 deletions(-)
create mode 100644 misc/tst-syslog-long-progname.c
create mode 100644 misc/tst-syslog-long-progname.root/postclean.req
diff --git a/misc/Makefile b/misc/Makefile
index fe0d49c1de..90b31952c5 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -289,7 +289,10 @@ tests-special += $(objpfx)tst-error1-mem.out \
$(objpfx)tst-allocate_once-mem.out
endif
-tests-container := tst-syslog
+tests-container := \
+ tst-syslog \
+ tst-syslog-long-progname \
+ # tests-container
CFLAGS-select.c += -fexceptions -fasynchronous-unwind-tables
CFLAGS-tsearch.c += $(uses-callbacks)
@@ -351,6 +354,9 @@ $(objpfx)tst-allocate_once-mem.out: $(objpfx)tst-allocate_once.out
$(common-objpfx)malloc/mtrace $(objpfx)tst-allocate_once.mtrace > $@; \
$(evaluate-test)
+tst-syslog-long-progname-ENV = GLIBC_TUNABLES=glibc.malloc.check=3 \
+ LD_PRELOAD=libc_malloc_debug.so.0
+
$(objpfx)tst-select: $(librt)
$(objpfx)tst-select-time64: $(librt)
$(objpfx)tst-pselect: $(librt)
diff --git a/misc/syslog.c b/misc/syslog.c
index 1b8cb722c5..814d224a1e 100644
--- a/misc/syslog.c
+++ b/misc/syslog.c
@@ -124,8 +124,9 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
{
/* Try to use a static buffer as an optimization. */
char bufs[1024];
- char *buf = NULL;
- size_t bufsize = 0;
+ char *buf = bufs;
+ size_t bufsize;
+
int msgoff;
int saved_errno = errno;
@@ -177,29 +178,50 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
#define SYSLOG_HEADER_WITHOUT_TS(__pri, __msgoff) \
"<%d>: %n", __pri, __msgoff
- int l;
+ int l, vl;
if (has_ts)
l = __snprintf (bufs, sizeof bufs,
SYSLOG_HEADER (pri, timestamp, &msgoff, pid));
else
l = __snprintf (bufs, sizeof bufs,
SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+
+ char *pos;
+ size_t len;
+
if (0 <= l && l < sizeof bufs)
{
- va_list apc;
- va_copy (apc, ap);
+ /* At this point, there is still a chance that we can print the
+ remaining part of the log into bufs and use that. */
+ pos = bufs + l;
+ len = sizeof (bufs) - l;
+ }
+ else
+ {
+ buf = NULL;
+ /* We already know that bufs is too small to use for this log message.
+ The next vsnprintf into bufs is used only to calculate the total
+ required buffer length. We will discard bufs contents and allocate
+ an appropriately sized buffer later instead. */
+ pos = bufs;
+ len = sizeof (bufs);
+ }
- /* Restore errno for %m format. */
- __set_errno (saved_errno);
+ {
+ va_list apc;
+ va_copy (apc, ap);
- int vl = __vsnprintf_internal (bufs + l, sizeof bufs - l, fmt, apc,
- mode_flags);
- if (0 <= vl && vl < sizeof bufs - l)
- buf = bufs;
- bufsize = l + vl;
+ /* Restore errno for %m format. */
+ __set_errno (saved_errno);
- va_end (apc);
- }
+ vl = __vsnprintf_internal (pos, len, fmt, apc, mode_flags);
+
+ if (!(0 <= vl && vl < len))
+ buf = NULL;
+
+ bufsize = l + vl;
+ va_end (apc);
+ }
if (buf == NULL)
{
diff --git a/misc/tst-syslog-long-progname.c b/misc/tst-syslog-long-progname.c
new file mode 100644
index 0000000000..88f37a8a00
--- /dev/null
+++ b/misc/tst-syslog-long-progname.c
@@ -0,0 +1,39 @@
+/* Test heap buffer overflow in syslog with long __progname (CVE-2023-6246)
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <syslog.h>
+#include <string.h>
+
+extern char * __progname;
+
+static int
+do_test (void)
+{
+ char long_progname[2048];
+
+ memset (long_progname, 'X', sizeof (long_progname) - 1);
+ long_progname[sizeof (long_progname) - 1] = '\0';
+
+ __progname = long_progname;
+
+ syslog (LOG_INFO, "Hello, World!");
+
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/tst-syslog-long-progname.root/postclean.req b/misc/tst-syslog-long-progname.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
--
2.33.0
|
