[v2] string: strerror must not return NULL (bug 30555)
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Commit Message
For strerror, this fixes commit 28aff047818eb1726394296d27b ("string:
Implement strerror in terms of strerror_l"). This commit avoids
returning NULL for strerror_l as well, although POSIX allows this
behavior for strerror_l.
---
v2: Change wording of comment as suggested by Andreas.
string/Makefile | 1 +
string/strerror_l.c | 13 +++++---
string/tst-strerror-fail.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 87 insertions(+), 4 deletions(-)
base-commit: 388ae538ddcb05c7d8966147b488a5f6e481656e
Comments
> For strerror, this fixes commit 28aff047818eb1726394296d27b ("string:
> Implement strerror in terms of strerror_l"). This commit avoids
> returning NULL for strerror_l as well, although POSIX allows this
> behavior for strerror_l.
This looks good to me.
Reviewed-by: Arjun Shankar <arjun@redhat.com>
>
> ---
> v2: Change wording of comment as suggested by Andreas.
> string/Makefile | 1 +
> string/strerror_l.c | 13 +++++---
> string/tst-strerror-fail.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 87 insertions(+), 4 deletions(-)
>
> diff --git a/string/Makefile b/string/Makefile
> index 0ad276cc6a..d3106d10a9 100644
> --- a/string/Makefile
> +++ b/string/Makefile
> @@ -178,6 +178,7 @@ tests := \
> tst-endian \
> tst-inlcall \
> tst-memmove-overflow \
> + tst-strerror-fail \
> tst-strfry \
> tst-strlcat \
> tst-strlcpy \
OK. Add new test to Makefile.
> diff --git a/string/strerror_l.c b/string/strerror_l.c
> index 7fe9b1d903..e5c8666198 100644
> --- a/string/strerror_l.c
> +++ b/string/strerror_l.c
We want to:
1. Try to return "Unknown error NNN" with the error number included.
2. If that fails, simply return "Unknown error" and not NULL.
> @@ -43,10 +43,15 @@ __strerror_l (int errnum, locale_t loc)
> struct tls_internal_t *tls_internal = __glibc_tls_internal ();
> free (tls_internal->strerror_l_buf);
Buffer freed here unconditionally.
> if (__asprintf (&tls_internal->strerror_l_buf, "%s%d",
> - translate ("Unknown error ", loc), errnum) == -1)
> - tls_internal->strerror_l_buf = NULL;
> -
> - err = tls_internal->strerror_l_buf;
Earlier, if asprintf failed, we set the thread local buffer pointer to
NULL and eventually returned that.
Now:
> + translate ("Unknown error ", loc), errnum) > 0)
OK. We consider any negative or 0 return value (i.e. 0 bytes printed)
from asprintf as error, which is safer than just considering -1 as an
error.
> + err = tls_internal->strerror_l_buf;
OK. Success case comes first with the negated condition above.
> + else
> + {
> + /* The memory was freed above. */
> + tls_internal->strerror_l_buf = NULL;
OK. Yes, we did just free the buffer, so we set it to NULL.
> + /* Provide a fallback translation. */
> + err = (char *) translate ("Unknown error", loc);
> + }
OK. We give up trying to return "Unknown error NNN" and simply
return "Unknown error" instead.
> }
> else
> err = (char *) translate (err, loc);
> diff --git a/string/tst-strerror-fail.c b/string/tst-strerror-fail.c
> new file mode 100644
> index 0000000000..e0fa45ab2b
> --- /dev/null
> +++ b/string/tst-strerror-fail.c
> @@ -0,0 +1,77 @@
> +/* Check that strerror, strerror_l do not return NULL on failure (bug 30555).
> + 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 <locale.h>
> +#include <stdbool.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/check.h>
> +#include <support/namespace.h>
> +#include <support/xdlfcn.h>
> +
> +/* Interposed malloc that can be used to inject allocation failures. */
> +
> +static volatile bool fail_malloc;
> +
> +void *
> +malloc (size_t size)
> +{
> + if (fail_malloc)
> + return NULL;
> +
> + static void *(*original_malloc) (size_t);
> + if (original_malloc == NULL)
> + original_malloc = xdlsym (RTLD_NEXT, "malloc");
> + return original_malloc (size);
> +}
OK.
> +
> +/* Callbacks for the actual tests. Use fork to run both tests with a
> + clean state. */
> +
> +static void
> +test_strerror (void *closure)
> +{
> + fail_malloc = true;
> + const char *s = strerror (999);
> + fail_malloc = false;
OK. Force malloc failure.
> + TEST_COMPARE_STRING (s, "Unknown error");
OK. Check for the correct string.
> +}
> +
> +static void
> +test_strerror_l (void *closure)
> +{
> + locale_t loc = newlocale (LC_ALL, "C", (locale_t) 0);
> + TEST_VERIFY (loc != (locale_t) 0);
> + fail_malloc = true;
> + const char *s = strerror_l (999, loc);
> + fail_malloc = false;
> + TEST_COMPARE_STRING (s, "Unknown error");
> + freelocale (loc);
> +}
OK. Same.
> +
> +static int
> +do_test (void)
> +{
> + support_isolate_in_subprocess (test_strerror, NULL);
> + support_isolate_in_subprocess (test_strerror_l, NULL);
> +
> + return 0;
> +}
> +
> +#include <support/test-driver.c>
OK. Both strerror and strerror_l shouldn't return NULL on malloc failure.
>
> base-commit: 388ae538ddcb05c7d8966147b488a5f6e481656e
>
@@ -178,6 +178,7 @@ tests := \
tst-endian \
tst-inlcall \
tst-memmove-overflow \
+ tst-strerror-fail \
tst-strfry \
tst-strlcat \
tst-strlcpy \
@@ -43,10 +43,15 @@ __strerror_l (int errnum, locale_t loc)
struct tls_internal_t *tls_internal = __glibc_tls_internal ();
free (tls_internal->strerror_l_buf);
if (__asprintf (&tls_internal->strerror_l_buf, "%s%d",
- translate ("Unknown error ", loc), errnum) == -1)
- tls_internal->strerror_l_buf = NULL;
-
- err = tls_internal->strerror_l_buf;
+ translate ("Unknown error ", loc), errnum) > 0)
+ err = tls_internal->strerror_l_buf;
+ else
+ {
+ /* The memory was freed above. */
+ tls_internal->strerror_l_buf = NULL;
+ /* Provide a fallback translation. */
+ err = (char *) translate ("Unknown error", loc);
+ }
}
else
err = (char *) translate (err, loc);
new file mode 100644
@@ -0,0 +1,77 @@
+/* Check that strerror, strerror_l do not return NULL on failure (bug 30555).
+ 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 <locale.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/xdlfcn.h>
+
+/* Interposed malloc that can be used to inject allocation failures. */
+
+static volatile bool fail_malloc;
+
+void *
+malloc (size_t size)
+{
+ if (fail_malloc)
+ return NULL;
+
+ static void *(*original_malloc) (size_t);
+ if (original_malloc == NULL)
+ original_malloc = xdlsym (RTLD_NEXT, "malloc");
+ return original_malloc (size);
+}
+
+/* Callbacks for the actual tests. Use fork to run both tests with a
+ clean state. */
+
+static void
+test_strerror (void *closure)
+{
+ fail_malloc = true;
+ const char *s = strerror (999);
+ fail_malloc = false;
+ TEST_COMPARE_STRING (s, "Unknown error");
+}
+
+static void
+test_strerror_l (void *closure)
+{
+ locale_t loc = newlocale (LC_ALL, "C", (locale_t) 0);
+ TEST_VERIFY (loc != (locale_t) 0);
+ fail_malloc = true;
+ const char *s = strerror_l (999, loc);
+ fail_malloc = false;
+ TEST_COMPARE_STRING (s, "Unknown error");
+ freelocale (loc);
+}
+
+static int
+do_test (void)
+{
+ support_isolate_in_subprocess (test_strerror, NULL);
+ support_isolate_in_subprocess (test_strerror_l, NULL);
+
+ return 0;
+}
+
+#include <support/test-driver.c>