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* [PATCH] malloc: Fix -Wuse-after-free warning in tst-mallocalign1 [BZ #26779]
@ 2022-01-31  5:21 Carlos O'Donell
  2022-01-31  5:32 ` Siddhesh Poyarekar
  2022-01-31  8:31 ` Andreas Schwab
  0 siblings, 2 replies; 6+ messages in thread
From: Carlos O'Donell @ 2022-01-31  5:21 UTC (permalink / raw)
  To: libc-alpha, joseph

The test leaks bits from the freed pointer via the return value
in ret, and the compiler correctly identifies this issue.
We switch the test to use TEST_VERIFY and terminate the test
if any of the pointers return an unexpected alignment.

This fixes another -Wuse-after-free error when compiling glibc
with gcc 12.

Tested on x86_64 and i686 without regression.
---
 malloc/tst-mallocalign1.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/malloc/tst-mallocalign1.c b/malloc/tst-mallocalign1.c
index 8bfd50c468..3116748e7e 100644
--- a/malloc/tst-mallocalign1.c
+++ b/malloc/tst-mallocalign1.c
@@ -20,6 +20,7 @@
 #include <stdlib.h>
 #include <inttypes.h>
 #include <malloc-size.h>
+#include <support/check.h>
 
 static void *
 test (size_t s)
@@ -31,41 +32,42 @@ test (size_t s)
   return p;
 }
 
+#define ALIGNED(p) (((uintptr_t )p & MALLOC_ALIGN_MASK) == 0)
+
 static int
 do_test (void)
 {
   void *p;
-  int ret = 0;
 
   p = test (2);
-  ret |= (uintptr_t) p & MALLOC_ALIGN_MASK;
+  TEST_VERIFY (ALIGNED (p));
   free (p);
 
   p = test (8);
-  ret |= (uintptr_t) p & MALLOC_ALIGN_MASK;
+  TEST_VERIFY (ALIGNED (p));
   free (p);
 
   p = test (13);
-  ret |= (uintptr_t) p & MALLOC_ALIGN_MASK;
+  TEST_VERIFY (ALIGNED (p));
   free (p);
 
   p = test (16);
-  ret |= (uintptr_t) p & MALLOC_ALIGN_MASK;
+  TEST_VERIFY (ALIGNED (p));
   free (p);
 
   p = test (23);
-  ret |= (uintptr_t) p & MALLOC_ALIGN_MASK;
+  TEST_VERIFY (ALIGNED (p));
   free (p);
 
   p = test (43);
-  ret |= (uintptr_t) p & MALLOC_ALIGN_MASK;
+  TEST_VERIFY (ALIGNED (p));
   free (p);
 
   p = test (123);
-  ret |= (uintptr_t) p & MALLOC_ALIGN_MASK;
+  TEST_VERIFY (ALIGNED (p));
   free (p);
 
-  return ret;
+  return 0;
 }
 
 #include <support/test-driver.c>
-- 
2.34.1


^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-02-01 17:08 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-01-31  5:21 [PATCH] malloc: Fix -Wuse-after-free warning in tst-mallocalign1 [BZ #26779] Carlos O'Donell
2022-01-31  5:32 ` Siddhesh Poyarekar
2022-01-31  6:00   ` Carlos O'Donell
2022-01-31  8:31 ` Andreas Schwab
2022-01-31 15:20   ` Carlos O'Donell
2022-02-01 17:08     ` Carlos O'Donell

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