+2017-08-30 Florian Weimer <fweimer@redhat.com>
+
+ [BZ #21754]
+ * malloc/malloc.c (malloc_printerr): Always terminate the process,
+ without printing a backtrace. Do not leak any information in the
+ error message.
+ * manual/memory.texi (Heap Consistency Checking): Update.
+ * manual/tunables.texi (Memory Allocation Tunables): Likewise.
+
2017-08-30 Florian Weimer <fweimer@redhat.com>
Do not scale NPTL tests with available number of CPUs.
* Optimized x86-64 asin, atan2, exp, expf, log, pow, atan, sin and tan
with FMA, contributed by Arjan van de Ven and H.J. Lu from Intel.
+* In order to support faster and safer process termination the malloc API
+ family of functions will no longer print a failure address and stack
+ backtrace after detecting heap corruption. The goal is to minimize the
+ amount of work done after corruption is detected and to avoid potential
+ security issues in continued process execution. Reducing shutdown time
+ leads to lower overall process restart latency, so there is benefit both
+ from a security and performance perspective.
+
Deprecated and removed features, and other changes affecting compatibility:
* On GNU/Linux, the obsolete Linux constant PTRACE_SEIZE_DEVEL is no longer
static void* _int_memalign(mstate, size_t, size_t);
static void* _mid_memalign(size_t, size_t, void *);
-static void malloc_printerr(int action, const char *str, void *ptr, mstate av);
+static void malloc_printerr(int action, const char *str, void *ptr, mstate av)
+ __attribute__ ((noreturn));
static void* internal_function mem2mem_check(void *p, size_t sz);
static int internal_function top_check(void);
if (ar_ptr)
set_arena_corrupt (ar_ptr);
- if ((action & 5) == 5)
- __libc_message ((action & 2) ? (do_abort | do_backtrace) : do_message,
- "%s\n", str);
- else if (action & 1)
- {
- char buf[2 * sizeof (uintptr_t) + 1];
-
- buf[sizeof (buf) - 1] = '\0';
- char *cp = _itoa_word ((uintptr_t) ptr, &buf[sizeof (buf) - 1], 16, 0);
- while (cp > buf)
- *--cp = '0';
-
- __libc_message ((action & 2) ? (do_abort | do_backtrace) : do_message,
- "*** Error in `%s': %s: 0x%s ***\n",
- __libc_argv[0] ? : "<unknown>", str, cp);
- }
- else if (action & 2)
- abort ();
+ __libc_message (do_abort, "%s\n", str);
+ __builtin_unreachable ();
}
/* We need a wrapper function for one of the additions of POSIX. */
Another possibility to check for and guard against bugs in the use of
@code{malloc}, @code{realloc} and @code{free} is to set the environment
-variable @code{MALLOC_CHECK_}. When @code{MALLOC_CHECK_} is set, a
-special (less efficient) implementation is used which is designed to be
-tolerant against simple errors, such as double calls of @code{free} with
-the same argument, or overruns of a single byte (off-by-one bugs). Not
-all such errors can be protected against, however, and memory leaks can
-result. If @code{MALLOC_CHECK_} is set to @code{0}, any detected heap
-corruption is silently ignored; if set to @code{1}, a diagnostic is
-printed on @code{stderr}; if set to @code{2}, @code{abort} is called
-immediately. This can be useful because otherwise a crash may happen
-much later, and the true cause for the problem is then very hard to
-track down.
+variable @code{MALLOC_CHECK_}. When @code{MALLOC_CHECK_} is set to a
+non-zero value, a special (less efficient) implementation is used which
+is designed to be tolerant against simple errors, such as double calls
+of @code{free} with the same argument, or overruns of a single byte
+(off-by-one bugs). Not all such errors can be protected against,
+however, and memory leaks can result.
+
+Any detected heap corruption results in immediate termination of the
+process.
There is one problem with @code{MALLOC_CHECK_}: in SUID or SGID binaries
it could possibly be exploited since diverging from the normal programs
This tunable supersedes the @env{MALLOC_CHECK_} environment variable and is
identical in features.
-Setting this tunable enables a special (less efficient) memory allocator for
-the malloc family of functions that is designed to be tolerant against simple
-errors such as double calls of free with the same argument, or overruns of a
-single byte (off-by-one bugs). Not all such errors can be protected against,
-however, and memory leaks can result. The following list describes the values
-that this tunable can take and the effect they have on malloc functionality:
-
-@itemize @bullet
-@item @code{0} Ignore all errors. The default allocator continues to be in
-use, but all errors are silently ignored.
-@item @code{1} Report errors. The alternate allocator is selected and heap
-corruption, if detected, is reported as diagnostic messages to @code{stderr}
-and the program continues execution.
-@item @code{2} Abort on errors. The alternate allocator is selected and if
-heap corruption is detected, the program is ended immediately by calling
-@code{abort}.
-@item @code{3} Fully enabled. The alternate allocator is selected and is fully
-functional. That is, if heap corruption is detected, a verbose diagnostic
-message is printed to @code{stderr} and the program is ended by calling
-@code{abort}.
-@end itemize
+Setting this tunable to a non-zero value enables a special (less
+efficient) memory allocator for the malloc family of functions that is
+designed to be tolerant against simple errors such as double calls of
+free with the same argument, or overruns of a single byte (off-by-one
+bugs). Not all such errors can be protected against, however, and memory
+leaks can result. Any detected heap corruption results in immediate
+termination of the process.
Like @env{MALLOC_CHECK_}, @code{glibc.malloc.check} has a problem in that it
diverges from normal program behavior by writing to @code{stderr}, which could
projects / thirdparty / glibc.git / commitdiff
