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Re: Buildbot failure in Wildebeest Builder on whole buildset


On Thu, Aug 29, 2019 at 04:23:24PM +0200, Mark Wielaard wrote:
> I am replacing some of the self test files with smaller
> executables/libraries as attached. Hopefully that will reduce the make
> check runtime under valgrind so builder don't time out.

That was interesting. It did bring down the make check times under
valgrind. But it also showed a memory leak in eu-nm! Triggered by
chance because we use different self-check binaries now :)

Fix attached and pushed to master.

Cheers,

Mark
>From df33285b60290fadefd140ee2fe616f750105d2f Mon Sep 17 00:00:00 2001
From: Mark Wielaard <mark@klomp.org>
Date: Thu, 29 Aug 2019 17:46:52 +0200
Subject: [PATCH] nm: Fix latent memory leak in show_symbols.

If there are just a handful of symbols then memory for them is
allocated on the stack, otherwise the memory is malloced. So before
freeing the memory we need to check the number of entries to know if
the memory was heap allocated or not. But since not all entries might
be used we might have decreased the number of entries to the number
we will actually show. Remember the original symbol entries to not
have a memory leak.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 src/ChangeLog | 5 +++++
 src/nm.c      | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/ChangeLog b/src/ChangeLog
index aeb62328..cb64f7d9 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2019-08-26  Mark Wielaard  <mark@klomp.org>
+
+	* nm.c (show_symbols): Remember nentries_orig and check before
+	freeing sym_mem.
+
 2019-07-05  Omar Sandoval  <osandov@fb.com>
 
 	* Makefile.am: Remove -ldl.
diff --git a/src/nm.c b/src/nm.c
index da1350b4..7f6cf2a2 100644
--- a/src/nm.c
+++ b/src/nm.c
@@ -1438,6 +1438,7 @@ show_symbols (int fd, Ebl *ebl, GElf_Ehdr *ehdr,
   free (demangle_buffer);
 #endif
   /* Now we know the exact number.  */
+  size_t nentries_orig = nentries;
   nentries = nentries_used;
 
   /* Sort the entries according to the users wishes.  */
@@ -1472,7 +1473,7 @@ show_symbols (int fd, Ebl *ebl, GElf_Ehdr *ehdr,
     }
 
   /* Free all memory.  */
-  if (nentries * sizeof (sym_mem[0]) >= MAX_STACK_ALLOC)
+  if (nentries_orig * sizeof (sym_mem[0]) >= MAX_STACK_ALLOC)
     free (sym_mem);
 
   obstack_free (&whereob, NULL);
-- 
2.20.1


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