mem-pool: invalidate memory on GF_FREE to aid debugging

Debugging where memory gets free'd with help from overwriting the memory
before it is free'd with some structures (repeatedly). The struct
mem_invalid starts with a magic value (0xdeadc0de), followed by a
pointer to the xlator, the mem-type. the size of the GF_?ALLOC()
requested area and the baseaddr pointer to what GF_?ALLOC() returned.

With these details, and the 'struct mem_header' that is placed when
calling GF_?ALLOC(), it is possible to identify overruns and possible
use-after-free. A memory dump (core) or running with a debugger is
needed to read the surrounding memory of corrupt structures.

This additional memory invalidation/poisoning needs to be enabled by
passing --enable-debug to ./configure.

Change-Id: I9f5f37dc4b5b59142adefc90897d32e89be67b82
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/10019
Reviewed-by: Venky Shankar <vshankar@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/libglusterfs/src/mem-pool.h b/libglusterfs/src/mem-pool.h
index 2bbb45ae8a7..81fb579a0ab 100644
--- a/libglusterfs/src/mem-pool.h
+++ b/libglusterfs/src/mem-pool.h
@@ -31,10 +31,10 @@
 #include <cmocka.h>
 #endif
 
-#define GF_MEM_HEADER_SIZE  (4 + sizeof (size_t) + sizeof (xlator_t *) + 4 + 8)
 #define GF_MEM_TRAILER_SIZE 8
 #define GF_MEM_HEADER_MAGIC  0xCAFEBABE
 #define GF_MEM_TRAILER_MAGIC 0xBAADF00D
+#define GF_MEM_INVALID_MAGIC 0xDEADC0DE
 
 struct mem_acct {
         uint32_t            num_types;
@@ -51,6 +51,25 @@ struct mem_acct_rec {
         gf_lock_t       lock;
 };
 
+struct mem_header {
+        uint32_t  type;
+        size_t    size;
+        void     *xlator;
+        uint32_t  magic;
+        int       padding[8];
+};
+
+#define GF_MEM_HEADER_SIZE  (sizeof (struct mem_header))
+
+#ifdef DEBUG
+struct mem_invalid {
+        uint32_t  magic;
+        void     *xlator;
+        uint32_t  type;
+        size_t    size;
+        void     *baseaddr;
+};
+#endif
 
 void *
 __gf_calloc (size_t cnt, size_t size, uint32_t type, const char *typestr);