malloc: tcache double free check

* malloc/malloc.c (tcache_entry): Add key field.
(tcache_put): Set it.
(tcache_get): Likewise.
(_int_free): Check for double free in tcache.
* malloc/tst-tcfree1.c: New.
* malloc/tst-tcfree2.c: New.
* malloc/Makefile: Run the new tests.
* manual/probes.texi: Document memory_tcache_double_free probe.

* dlfcn/dlerror.c (check_free): Prevent double frees.

1 files changed, 12 insertions, 0 deletions

diff --git a/manual/probes.texi b/manual/probes.texi
index ab2a3102bb..0ea560ed78 100644
--- a/manual/probes.texi
+++ b/manual/probes.texi
@@ -243,6 +243,18 @@ This probe is triggered when the
 value of this tunable.
 @end deftp
 
+@deftp Probe memory_tcache_double_free (void *@var{$arg1}, int @var{$arg2})
+This probe is triggered when @code{free} determines that the memory
+being freed has probably already been freed, and resides in the
+per-thread cache.  Note that there is an extremely unlikely chance
+that this probe will trigger due to random payload data remaining in
+the allocated memory matching the key used to detect double frees.
+This probe actually indicates that an expensive linear search of the
+tcache, looking for a double free, has happened.  Argument @var{$arg1}
+is the memory location as passed to @code{free}, Argument @var{$arg2}
+is the tcache bin it resides in.
+@end deftp
+
 @node Mathematical Function Probes
 @section Mathematical Function Probes