From: Niklas Hambüchen <mail@nh2.me>
Date: Thu, 8 Aug 2019 20:02:27 +0000 (+0200)
Subject: malloc: Fix missing accounting of top chunk in malloc_info [BZ #24026]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5f620768fbdae75f71af78852be228ad5577623d;p=thirdparty%2Fglibc.git

malloc: Fix missing accounting of top chunk in malloc_info [BZ #24026]

Fixes `<total type="rest" size="..."> incorrectly showing as 0 most
of the time.

The rest value being wrong is significant because to compute the
actual amount of memory handed out via malloc, the user must subtract
it from <system type="current" size="...">. That result being wrong
makes investigating memory fragmentation issues like
<https://bugzilla.redhat.com/show_bug.cgi?id=843478> close to
impossible.

(cherry picked from commit b6d2c4475d5abc05dd009575b90556bdd3c78ad0)
---

diff --git a/ChangeLog b/ChangeLog
index 43c9a70ed10..e1d8fd3c66b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2019-08-08  Niklas Hambüchen  <mail@nh2.me>
+	    Carlos O'Donell  <carlos@redhat.com>
+
+	[BZ #24026]
+	* malloc/malloc.c (__malloc_info): Account for top chunk.
+
 2019-11-01  Dragan Mladjenovic  <dmladjenovic@wavecomp.com>
 
 	* sysdeps/unix/sysv/linux/mips/Makefile
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 343d89f4893..0e65d636cdd 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5406,6 +5406,12 @@ __malloc_info (int options, FILE *fp)
 
       __libc_lock_lock (ar_ptr->mutex);
 
+      /* Account for top chunk.  The top-most available chunk is
+	 treated specially and is never in any bin. See "initial_top"
+	 comments.  */
+      avail = chunksize (ar_ptr->top);
+      nblocks = 1;  /* Top always exists.  */
+
       for (size_t i = 0; i < NFASTBINS; ++i)
 	{
 	  mchunkptr p = fastbin (ar_ptr, i);