[Bug libc/4630] New: assertion failure in do_check_malloc_state caused by the non-continuous case in sysMALLOc()

["philipp dot tomsich at theobroma-systems dot com" <sourceware-bugzilla at sourceware dot org>]

We've hit the assertion "malloc.c:2884: do_check_malloc_state: Assertion `(unsigned long)(av-
>system_mem) <= (unsigned long)(av->max_system_mem)' failed." with glibc-2.6 (with 
MALLOC_DEBUG defined to 1) on Linux 2.6. 

Our application frequently uses sbrk()/mmap() directly and exercises the non-continuous case in 
sYSMALLOc(). In rare cases, do_check_malloc_state() will be called through _int_free() at malloc.c:3333 
with (av->system_mem) > (av->max_system_mem), when av->system_mem is increased in 
sYSMALLOc at malloc.c:3299, malloc.c:3232 and malloc.c:3188. 

I'm including a patch to adjust av->max_system_mem to a consistent malloc state (earlier than at 
malloc.c:3352) if _int_free() will be called. The patch will introduce no overhead if MALLOC_DEBUG is 
not defined.

--- glibc-2.6-vanilla/malloc/malloc.c   2007-05-15 03:51:17.000000000 +0200
+++ glibc-2.6/malloc/malloc.c   2007-06-12 16:05:48.000000000 +0200
@@ -3330,6 +3330,17 @@
 
           /* If possible, release the rest. */
           if (old_size >= MINSIZE) {
+
+#if MALLOC_DEBUG
+           /* Restore a consistent state early to avoid failures with
+              debug builds _int_free() calls sYSTRIm() (and sYSTRIm()
+              asserts on inconistencies) */
+
+           if ((unsigned long)(av->system_mem) > 
+               (unsigned long)(av->max_system_mem))
+             av->max_system_mem = av->system_mem;
+#endif
+
             _int_free(av, chunk2mem(old_top));
           }
 
--- glibc-2.6-vanilla/ChangeLog 2007-05-15 08:49:29.000000000 +0200
+++ glibc-2.6/ChangeLog 2007-06-12 16:04:55.000000000 +0200
@@ -0,0 +1,7 @@
+2007-06-12  Philipp Tomsich  <philipp.tomsich@theobroma-systems.com>
+
+       * malloc/malloc.c (sYSMALLOc): Added an early adjustment
+       (conditional to DEBUG_MALLOC) of av->max_system_mem for the
+       non-continuous case to avoid triggering an assertion in
+       check_malloc_state().
+

-- 
           Summary: assertion failure in do_check_malloc_state caused by the
                    non-continuous case in sysMALLOc()
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: philipp dot tomsich at theobroma-systems dot com
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: i686-linux-gnu
  GCC host triplet: mipsel-linux-gnu
GCC target triplet: mipsel-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=4630

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