[v2] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
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| Context |
Check |
Description |
| dj/TryBot-apply_patch |
success
|
Patch applied to master at the time it was sent
|
| dj/TryBot-32bit |
success
|
Build for i686
|
Commit Message
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>
---
stdlib/Makefile | 1 +
stdlib/canonicalize.c | 12 ++++-
stdlib/tst-realpath-toolong.c | 84 +++++++++++++++++++++++++++++++++++
3 files changed, 95 insertions(+), 2 deletions(-)
create mode 100644 stdlib/tst-realpath-toolong.c
Comments
On 13/01/2022 02:59, Siddhesh Poyarekar via Libc-alpha 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>
CCing Paul because I believe he might want to fix it on gnulib as well.
Looks good, it just need to fix the Hurd build below.
> ---
> stdlib/Makefile | 1 +
> stdlib/canonicalize.c | 12 ++++-
> stdlib/tst-realpath-toolong.c | 84 +++++++++++++++++++++++++++++++++++
> 3 files changed, 95 insertions(+), 2 deletions(-)
> create mode 100644 stdlib/tst-realpath-toolong.c
>
> diff --git a/stdlib/Makefile b/stdlib/Makefile
> index 52e4d8cf19..897d4ea79d 100644
> --- a/stdlib/Makefile
> +++ b/stdlib/Makefile
> @@ -108,6 +108,7 @@ tests := bug-fmtmsg1 \
> tst-random \
> tst-random2 \
> tst-realpath \
> + tst-realpath-toolong \
> tst-secure-getenv \
> tst-setcontext \
> tst-setcontext2 \
Ok.
> 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);
Ok.
> diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
> new file mode 100644
> index 0000000000..71c0829a80
> --- /dev/null
> +++ b/stdlib/tst-realpath-toolong.c
> @@ -0,0 +1,84 @@
> +/* 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."
> +size_t nest_count;
> +char dir[NAME_MAX + 1];
> +char *base;
> +
> +static void
> +delete_subdirectories (const char *name)
> +{
> + TEST_VERIFY (chdir (name) == 0);
> + if (--nest_count > 0)
> + delete_subdirectories (dir);
> + TEST_VERIFY (chdir ("..") == 0);
> + TEST_VERIFY (rmdir (name) == 0);
> +}
> +
> +static void
> +do_cleanup (void)
> +{
> + TEST_VERIFY (chdir (base) == 0);
> + if (nest_count > 0)
> + delete_subdirectories (dir);
> +}
> +
> +int
> +do_test (void)
> +{
> + base = support_create_temp_directory (BASENAME);
> +
> + TEST_VERIFY_EXIT (chdir (base) == 0);
> +
> + memset (dir, 'X', sizeof (dir) - 1);
> + dir[NAME_MAX] = '\0';
> +
> + /* Create directories and descend into them so that the final path is larger
> + than PATH_MAX. */
> + for (nest_count = 0; nest_count <= PATH_MAX / sizeof (dir); nest_count++)
This fails to build on Hurd, so I am not sure if it would be better to just
set it as UNSUPPORTED in this case or use the assumption on realpath:
#ifdef PATH_MAX
size_t path_max = PATH_MAX;
#else
size_t path_max = pathconf ("/", _PC_PATH_MAX);
path_max = path_max < 0 ? 1024 : path_max < ? path_max : PTRDIFF_MAX;
#endif
> + {
> + TEST_VERIFY_EXIT (mkdir (dir, S_IRWXU) == 0);
> + TEST_VERIFY_EXIT (chdir (dir) == 0);
> + }
> +
> + 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);
> +
> + do_cleanup ();
> + free (base);
> + return 0;
> +}
> +
> +#define CLEANUP_HANDLER do_cleanup
> +#include <support/test-driver.c>
On 13/01/2022 19:30, Adhemerval Zanella wrote:
>
>
> On 13/01/2022 02:59, Siddhesh Poyarekar via Libc-alpha 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>
>
> CCing Paul because I believe he might want to fix it on gnulib as well.
>
> Looks good, it just need to fix the Hurd build below.
>
>> ---
>> stdlib/Makefile | 1 +
>> stdlib/canonicalize.c | 12 ++++-
>> stdlib/tst-realpath-toolong.c | 84 +++++++++++++++++++++++++++++++++++
>> 3 files changed, 95 insertions(+), 2 deletions(-)
>> create mode 100644 stdlib/tst-realpath-toolong.c
>>
>> diff --git a/stdlib/Makefile b/stdlib/Makefile
>> index 52e4d8cf19..897d4ea79d 100644
>> --- a/stdlib/Makefile
>> +++ b/stdlib/Makefile
>> @@ -108,6 +108,7 @@ tests := bug-fmtmsg1 \
>> tst-random \
>> tst-random2 \
>> tst-realpath \
>> + tst-realpath-toolong \
>> tst-secure-getenv \
>> tst-setcontext \
>> tst-setcontext2 \
>
> Ok.
>
>> 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);
>
> Ok.
>
>> diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
>> new file mode 100644
>> index 0000000000..71c0829a80
>> --- /dev/null
>> +++ b/stdlib/tst-realpath-toolong.c
>> @@ -0,0 +1,84 @@
>> +/* 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."
>> +size_t nest_count;
>> +char dir[NAME_MAX + 1];
>> +char *base;
>> +
>> +static void
>> +delete_subdirectories (const char *name)
>> +{
>> + TEST_VERIFY (chdir (name) == 0);
>> + if (--nest_count > 0)
>> + delete_subdirectories (dir);
>> + TEST_VERIFY (chdir ("..") == 0);
>> + TEST_VERIFY (rmdir (name) == 0);
>> +}
>> +
>> +static void
>> +do_cleanup (void)
>> +{
>> + TEST_VERIFY (chdir (base) == 0);
>> + if (nest_count > 0)
>> + delete_subdirectories (dir);
>> +}
>> +
>> +int
>> +do_test (void)
>> +{
>> + base = support_create_temp_directory (BASENAME);
>> +
>> + TEST_VERIFY_EXIT (chdir (base) == 0);
>> +
>> + memset (dir, 'X', sizeof (dir) - 1);
>> + dir[NAME_MAX] = '\0';
>> +
>> + /* Create directories and descend into them so that the final path is larger
>> + than PATH_MAX. */
>> + for (nest_count = 0; nest_count <= PATH_MAX / sizeof (dir); nest_count++)
>
> This fails to build on Hurd, so I am not sure if it would be better to just
> set it as UNSUPPORTED in this case or use the assumption on realpath:
>
> #ifdef PATH_MAX
> size_t path_max = PATH_MAX;
> #else
> size_t path_max = pathconf ("/", _PC_PATH_MAX);
> path_max = path_max < 0 ? 1024 : path_max < ? path_max : PTRDIFF_MAX;
> #endif
Ahh yes, I'll fix up the test for hurd using this snippet.
Thanks,
Siddhesh
@@ -108,6 +108,7 @@ tests := bug-fmtmsg1 \
tst-random \
tst-random2 \
tst-realpath \
+ tst-realpath-toolong \
tst-secure-getenv \
tst-setcontext \
tst-setcontext2 \
@@ -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);
new file mode 100644
@@ -0,0 +1,84 @@
+/* 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."
+size_t nest_count;
+char dir[NAME_MAX + 1];
+char *base;
+
+static void
+delete_subdirectories (const char *name)
+{
+ TEST_VERIFY (chdir (name) == 0);
+ if (--nest_count > 0)
+ delete_subdirectories (dir);
+ TEST_VERIFY (chdir ("..") == 0);
+ TEST_VERIFY (rmdir (name) == 0);
+}
+
+static void
+do_cleanup (void)
+{
+ TEST_VERIFY (chdir (base) == 0);
+ if (nest_count > 0)
+ delete_subdirectories (dir);
+}
+
+int
+do_test (void)
+{
+ base = support_create_temp_directory (BASENAME);
+
+ TEST_VERIFY_EXIT (chdir (base) == 0);
+
+ memset (dir, 'X', sizeof (dir) - 1);
+ dir[NAME_MAX] = '\0';
+
+ /* Create directories and descend into them so that the final path is larger
+ than PATH_MAX. */
+ for (nest_count = 0; nest_count <= PATH_MAX / sizeof (dir); nest_count++)
+ {
+ TEST_VERIFY_EXIT (mkdir (dir, S_IRWXU) == 0);
+ TEST_VERIFY_EXIT (chdir (dir) == 0);
+ }
+
+ 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);
+
+ do_cleanup ();
+ free (base);
+ return 0;
+}
+
+#define CLEANUP_HANDLER do_cleanup
+#include <support/test-driver.c>