[PATCH 01/10] malloc: Abort on heap corruption, without a backtrace [BZ #21754]
Siddhesh Poyarekar
siddhesh@sourceware.org
Sun Jan 1 00:00:00 GMT 2017
From: Florian Weimer <fweimer@redhat.com>
The stack trace printing caused deadlocks and has been itself been
targeted by code execution exploits.
(cherry-picked from ec2c1fcefb200c6cb7e09553f3c6af8815013d83)
---
ChangeLog | 9 +++++++++
NEWS | 10 ++++++++++
malloc/malloc.c | 23 ++++-------------------
manual/memory.texi | 20 +++++++++-----------
manual/tunables.texi | 28 +++++++---------------------
5 files changed, 39 insertions(+), 51 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 812c538..7a35bff 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+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.
+
2017-11-17 Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
* sysdeps/powerpc/bits/hwcap.h (PPC_FEATURE2_HTM_NO_SUSPEND): New
diff --git a/NEWS b/NEWS
index e7b62a8..359465f 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,16 @@ using `glibc' in the "product" field.
Version 2.26.1
+Major new features:
+
+* 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.
+
Security related changes:
CVE-2009-5064: The ldd script would sometimes run the program under
diff --git a/malloc/malloc.c b/malloc/malloc.c
index dd9f699..c91fc09 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1019,7 +1019,8 @@ static void* _int_realloc(mstate, mchunkptr, INTERNAL_SIZE_T,
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);
@@ -5399,24 +5400,8 @@ malloc_printerr (int action, const char *str, void *ptr, mstate ar_ptr)
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. */
diff --git a/manual/memory.texi b/manual/memory.texi
index 82f4738..13cce7a 100644
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -1309,17 +1309,15 @@ The block was already freed.
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
diff --git a/manual/tunables.texi b/manual/tunables.texi
index 3c19567..b09e3fe 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -71,27 +71,13 @@ following tunables in the @code{malloc} namespace:
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
--
2.7.5
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