diff mbox series

[2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]

Message ID 20220118090728.1825487-3-siddhesh@sourceware.org
State Superseded
Headers show
Series Fixes for CVE-2021-3998 and CVE-2021-3999 | expand

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Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

Siddhesh Poyarekar Jan. 18, 2022, 9:07 a.m. UTC
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.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
 NEWS                          |  4 +++
 stdlib/Makefile               |  1 +
 stdlib/canonicalize.c         | 12 +++++++--
 stdlib/tst-realpath-toolong.c | 48 +++++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+), 2 deletions(-)
 create mode 100644 stdlib/tst-realpath-toolong.c

Comments

Adhemerval Zanella Jan. 18, 2022, 7:43 p.m. UTC | #1
On 18/01/2022 06:07, Siddhesh Poyarekar wrote:
> 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.
> 
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  NEWS                          |  4 +++
>  stdlib/Makefile               |  1 +
>  stdlib/canonicalize.c         | 12 +++++++--
>  stdlib/tst-realpath-toolong.c | 48 +++++++++++++++++++++++++++++++++++
>  4 files changed, 63 insertions(+), 2 deletions(-)
>  create mode 100644 stdlib/tst-realpath-toolong.c
> 
> diff --git a/NEWS b/NEWS
> index 38802f0673..5c63cef156 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -163,6 +163,10 @@ Security related changes:
>    CVE-2022-23218: Passing an overlong file name to the svcunix_create
>    legacy function could result in a stack-based buffer overflow.
>  
> +  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.
> +
>  The following bugs are resolved with this release:
>  
>    [The release manager will add the list generated by
> diff --git a/stdlib/Makefile b/stdlib/Makefile
> index 1e81f98fac..8236741984 100644
> --- a/stdlib/Makefile
> +++ b/stdlib/Makefile
> @@ -109,6 +109,7 @@ tests := \
>    tst-random \
>    tst-random2 \
>    tst-realpath \
> +  tst-realpath-toolong \
>    tst-secure-getenv \
>    tst-setcontext \
>    tst-setcontext2 \
> diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
> index f36bdf4c76..732dc7ea46 100644
> --- a/stdlib/canonicalize.c
> +++ b/stdlib/canonicalize.c
> @@ -400,8 +400,16 @@ realpath_stk (const char *name, char *resolved,
>  
>  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/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
> new file mode 100644
> index 0000000000..f10653f05b
> --- /dev/null
> +++ b/stdlib/tst-realpath-toolong.c
> @@ -0,0 +1,48 @@
> +/* 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 * const res = realpath (".", buf);
> +
> +  /* canonicalize.c states that if the real path is >= PATH_MAX, then
> +     realpath returns NULL and sets ENAMETOOLONG.  */
> +  TEST_VERIFY_EXIT (res == NULL && errno == ENAMETOOLONG);
> +
> +  free (base);
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
diff mbox series

Patch

diff --git a/NEWS b/NEWS
index 38802f0673..5c63cef156 100644
--- a/NEWS
+++ b/NEWS
@@ -163,6 +163,10 @@  Security related changes:
   CVE-2022-23218: Passing an overlong file name to the svcunix_create
   legacy function could result in a stack-based buffer overflow.
 
+  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.
+
 The following bugs are resolved with this release:
 
   [The release manager will add the list generated by
diff --git a/stdlib/Makefile b/stdlib/Makefile
index 1e81f98fac..8236741984 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -109,6 +109,7 @@  tests := \
   tst-random \
   tst-random2 \
   tst-realpath \
+  tst-realpath-toolong \
   tst-secure-getenv \
   tst-setcontext \
   tst-setcontext2 \
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index f36bdf4c76..732dc7ea46 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -400,8 +400,16 @@  realpath_stk (const char *name, char *resolved,
 
 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/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
new file mode 100644
index 0000000000..f10653f05b
--- /dev/null
+++ b/stdlib/tst-realpath-toolong.c
@@ -0,0 +1,48 @@ 
+/* 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 * const res = realpath (".", buf);
+
+  /* canonicalize.c states that if the real path is >= PATH_MAX, then
+     realpath returns NULL and sets ENAMETOOLONG.  */
+  TEST_VERIFY_EXIT (res == NULL && errno == ENAMETOOLONG);
+
+  free (base);
+  return 0;
+}
+
+#include <support/test-driver.c>