diff options
| -rw-r--r-- | debug/Makefile | 5 | ||||
| -rw-r--r-- | debug/tst-sprintf-fortify-unchecked.c | 126 | ||||
| -rw-r--r-- | include/printf_buffer.h | 19 | ||||
| -rw-r--r-- | libio/iovsprintf.c | 15 |
4 files changed, 155 insertions, 10 deletions
diff --git a/debug/Makefile b/debug/Makefile index 13f15d1..52f9a78 100644 --- a/debug/Makefile +++ b/debug/Makefile @@ -200,6 +200,10 @@ LDFLAGS-tst-backtrace6 = -rdynamic CFLAGS-tst-ssp-1.c += -fstack-protector-all +# Disable compiler optimizations around vsprintf (the function under test). +CFLAGS-tst-sprintf-fortify-unchecked.c = \ + -fno-builtin-vsprintf -fno-builtin-__vsprintf_chk + tests = backtrace-tst \ tst-longjmp_chk \ test-strcpy_chk \ @@ -211,6 +215,7 @@ tests = backtrace-tst \ tst-backtrace5 \ tst-backtrace6 \ tst-realpath-chk \ + tst-sprintf-fortify-unchecked \ $(tests-all-chk) tests-time64 += \ diff --git a/debug/tst-sprintf-fortify-unchecked.c b/debug/tst-sprintf-fortify-unchecked.c new file mode 100644 index 0000000..7c7bd1b --- /dev/null +++ b/debug/tst-sprintf-fortify-unchecked.c @@ -0,0 +1,126 @@ +/* Tests for fortified sprintf with unknown buffer bounds (bug 30039). + 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 <printf.h> +#include <stdarg.h> +#include <stdio.h> +#include <string.h> +#include <support/check.h> + +/* This test is not built with _FORTIFY_SOURCE. Instead it calls the + appropriate implementation directly. The fortify mode is specified + in this variable. */ +static int fortify_mode; + +/* This does not handle long-double redirects etc., but we test only + format strings that stay within the confines of the base + implementation. */ +int __vsprintf_chk (char *s, int flag, size_t slen, const char *format, + va_list ap); + +/* Invoke vsprintf or __vsprintf_chk according to fortify_mode. */ +static int +my_vsprintf (char *buf, const char *format, va_list ap) +{ + int result; + if (fortify_mode == 0) + result = vsprintf (buf, format, ap); + else + /* Call the fortified version with an unspecified length. */ + result = __vsprintf_chk (buf, fortify_mode - 1, -1, format, ap); + return result; +} + +/* Run one test, with the specified expected output. */ +static void __attribute ((format (printf, 2, 3))) +do_check (const char *expected, const char *format, ...) +{ + va_list ap; + va_start (ap, format); + + char buf_expected[24]; + memset (buf_expected, '@', sizeof (buf_expected)); + TEST_VERIFY (strlen (expected) < sizeof (buf_expected)); + strcpy (buf_expected, expected); + + char buf[sizeof (buf_expected)]; + memset (buf, '@', sizeof (buf)); + + int ret = my_vsprintf (buf, format, ap); + TEST_COMPARE_BLOB (buf_expected, sizeof (buf_expected), buf, sizeof (buf)); + TEST_COMPARE (ret, strlen (expected)); + + va_end (ap); +} + +/* Run the tests in all fortify modes. */ +static void +do_tests (void) +{ + for (fortify_mode = 0; fortify_mode <= 3; ++fortify_mode) + { + do_check ("0", "%d", 0); + do_check ("-2147483648", "%d", -2147483647 - 1); + do_check ("-9223372036854775808", "%lld", -9223372036854775807LL - 1); + do_check ("", "%s", ""); + do_check (" ", "%22s", ""); + do_check ("XXXXXXXXXXXXXXXXXXXXXX", "%s", "XXXXXXXXXXXXXXXXXXXXXX"); + do_check ("1.125000", "%f", 1.125); + do_check ("1.125", "%g", 1.125); + do_check ("1.125", "%.8g", 1.125); + } +} + +/* printf callback that falls back to the glibc-supplied + implementation. */ +static int +dummy_printf_function (FILE *__stream, + const struct printf_info *__info, + const void *const *__args) +{ + return -2; /* Request fallback. */ +} + +/* Likewise for the type information. */ +static int +dummy_arginfo_function (const struct printf_info *info, + size_t n, int *argtypes, int *size) +{ + return -1; /* Request fallback. */ +} + +static int +do_test (void) +{ + do_tests (); + + /* Activate __printf_function_invoke mode. */ + register_printf_specifier ('d', dummy_printf_function, + dummy_arginfo_function); + register_printf_specifier ('g', dummy_printf_function, + dummy_arginfo_function); + register_printf_specifier ('s', dummy_printf_function, + dummy_arginfo_function); + + /* Rerun the tests with callback functions. */ + do_tests (); + + return 0; +} + +#include <support/test-driver.c> diff --git a/include/printf_buffer.h b/include/printf_buffer.h index 55feebf..4d787e4 100644 --- a/include/printf_buffer.h +++ b/include/printf_buffer.h @@ -115,19 +115,28 @@ __printf_buffer_has_failed (struct __printf_buffer *buf) return buf->mode == __printf_buffer_mode_failed; } -/* Initialization of a buffer, using the memory region from [BASE, BASE +LEN) - as the initial buffer contents. LEN can be zero. */ +/* Initialization of a buffer, using the memory region from [BASE, + END) as the initial buffer contents. */ static inline void -__printf_buffer_init (struct __printf_buffer *buf, char *base, size_t len, - enum __printf_buffer_mode mode) +__printf_buffer_init_end (struct __printf_buffer *buf, char *base, char *end, + enum __printf_buffer_mode mode) { buf->write_base = base; buf->write_ptr = base; - buf->write_end = base + len; + buf->write_end = end; buf->written = 0; buf->mode = mode; } +/* Initialization of a buffer, using the memory region from [BASE, BASE +LEN) + as the initial buffer contents. LEN can be zero. */ +static inline void +__printf_buffer_init (struct __printf_buffer *buf, char *base, size_t len, + enum __printf_buffer_mode mode) +{ + __printf_buffer_init_end (buf, base, base + len, mode); +} + /* Called by printf_buffer_putc for a full buffer. */ void __printf_buffer_putc_1 (struct __printf_buffer *buf, char ch) attribute_hidden; diff --git a/libio/iovsprintf.c b/libio/iovsprintf.c index 8d53e40..9a4f59a 100644 --- a/libio/iovsprintf.c +++ b/libio/iovsprintf.c @@ -45,14 +45,19 @@ __vsprintf_internal (char *string, size_t maxlen, if ((mode_flags & PRINTF_CHK) != 0) { string[0] = '\0'; - __printf_buffer_init (&buf, string, maxlen, + /* In some cases, __sprintf_chk is called with an unknown buffer + size (the special value -1). Prevent pointer wraparound in + this case and saturate to the end of the address space. */ + uintptr_t end; + if (__builtin_add_overflow ((uintptr_t) string, maxlen, &end)) + end = -1; + __printf_buffer_init_end (&buf, string, (char *) end, __printf_buffer_mode_sprintf_chk); } else - { - __printf_buffer_init (&buf, string, 0, __printf_buffer_mode_sprintf); - buf.write_end = (char *) ~(uintptr_t) 0; /* End of address space. */ - } + /* Use end of address space. */ + __printf_buffer_init_end (&buf, string, (char *) ~(uintptr_t) 0, + __printf_buffer_mode_sprintf); __printf_buffer (&buf, format, args, mode_flags); |