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From f7a79879c0b2bef0dadd6caaaeeb0d26423e04e5 Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Thu, 13 Jan 2022 11:28:36 +0530
Subject: [PATCH] realpath: Set errno to ENAMETOOLONG for result larger than
PATH_MAX [BZ #28770]
realpath returns an allocated string when the result exceeds PATH_MAX,
which is unexpected when its second argument is not NULL. This results
in the second argument (resolved) being uninitialized and also results
in a memory leak since the caller expects resolved to be the same as the
returned value.
Return NULL and set errno to ENAMETOOLONG if the result exceeds
PATH_MAX. This fixes [BZ #28770], which is CVE-2021-3998.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
(cherry picked from commit ee8d5e33adb284601c00c94687bc907e10aec9bb)
Upstream-Status: Backport [https://sourceware.org/git/?p=glibc.git;a=commit;h=f7a79879c0b2bef0dadd6caaaeeb0d26423e04e5]
CVE: CVE-2021-3998
Signed-off-by: Pgowda <pgowda.cve@gmail.com>
---
NEWS | 4 +++
stdlib/Makefile | 1 +
stdlib/canonicalize.c | 12 +++++++--
stdlib/tst-realpath-toolong.c | 49 +++++++++++++++++++++++++++++++++++
4 files changed, 64 insertions(+), 2 deletions(-)
create mode 100644 stdlib/tst-realpath-toolong.c
diff --git a/NEWS b/NEWS
index 7e773bd005..b4f81c2668 100644
--- a/NEWS
+++ b/NEWS
@@ -210,6 +210,10 @@ Security related changes:
legacy function could result in a stack-based buffer overflow when
using the "unix" protocol. Reported by Martin Sebor.
+ CVE-2021-3998: Passing a path longer than PATH_MAX to the realpath
+ function could result in a memory leak and potential access of
+ uninitialized memory. Reported by Qualys.
+
The following bugs are resolved with this release:
[4737] libc: fork is not async-signal-safe
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index 698f9ede25..7a23a51b3a 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -400,8 +400,16 @@ realpath_stk (const char *name, char *re
error:
*dest++ = '\0';
- if (resolved != NULL && dest - rname <= get_path_max ())
- rname = strcpy (resolved, rname);
+ if (resolved != NULL)
+ {
+ if (dest - rname <= get_path_max ())
+ rname = strcpy (resolved, rname);
+ else
+ {
+ failed = true;
+ __set_errno (ENAMETOOLONG);
+ }
+ }
error_nomem:
scratch_buffer_free (&extra_buffer);
diff --git a/stdlib/Makefile b/stdlib/Makefile
index 9bb5c221e8..a4ac30d1f6 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -88,7 +88,8 @@ tests := tst-strtol tst-strtod testmb t
tst-swapcontext1 tst-setcontext4 tst-setcontext5 \
tst-setcontext6 tst-setcontext7 tst-setcontext8 \
tst-setcontext9 tst-bz20544 tst-canon-bz26341 \
- tst-realpath
+ tst-realpath \
+ tst-realpath-toolong
tests-internal := tst-strtod1i tst-strtod3 tst-strtod4 tst-strtod5i \
tst-tls-atexit tst-tls-atexit-nodelete
diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
new file mode 100644
index 0000000000..8bed772460
--- /dev/null
+++ b/stdlib/tst-realpath-toolong.c
@@ -0,0 +1,49 @@
+/* Verify that realpath returns NULL with ENAMETOOLONG if the result exceeds
+ NAME_MAX.
+ Copyright The GNU Toolchain Authors.
+ 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 <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#define BASENAME "tst-realpath-toolong."
+
+int
+do_test (void)
+{
+ char *base = support_create_and_chdir_toolong_temp_directory (BASENAME);
+
+ char buf[PATH_MAX + 1];
+ const char *res = realpath (".", buf);
+
+ /* canonicalize.c states that if the real path is >= PATH_MAX, then
+ realpath returns NULL and sets ENAMETOOLONG. */
+ TEST_VERIFY (res == NULL);
+ TEST_VERIFY (errno == ENAMETOOLONG);
+
+ free (base);
+ return 0;
+}
+
+#include <support/test-driver.c>
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