[PATCH release/2.41/master] stdlib: resolve a double lock init issue after fork [BZ #32994]

[Mark Wielaard]

From: Davide Cavalca <davide@cavalca.name>

The __abort_fork_reset_child (introduced in
d40ac01cbbc66e6d9dbd8e3485605c63b2178251) call resets the lock after the
fork. This causes a DRD regression in valgrind
(https://bugs.kde.org/show_bug.cgi?id=503668), as it's effectively a
double initialization, despite it being actually ok in this case. As
suggested in https://sourceware.org/bugzilla/show_bug.cgi?id=32994#c2
we replace it here with a memcpy of another initialized lock instead,
which makes valgrind happy.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
(cherry picked from commit d9a348d0927c7a1aec5caf3df3fcd36956b3eb23)
---
 NEWS           | 1 +
 stdlib/abort.c | 6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 89d0935bebf4..1a58f3e4e456 100644
--- a/NEWS
+++ b/NEWS
@@ -32,6 +32,7 @@ The following bugs were resolved with this release:
   [32981] ports: elf/tst-execstack-prog-static-tunable fails on
     sparc64-linux-gnu
   [32987] elf: Fix subprocess status handling for tst-dlopen-sgid
+  [32994] stdlib: resolve a double lock init issue after fork
   [33164] iconv -o should not create executable files
   [33185] Fix double-free after allocation failure in regcomp
 
diff --git a/stdlib/abort.c b/stdlib/abort.c
index caa9e6dc0494..904244a2fb5b 100644
--- a/stdlib/abort.c
+++ b/stdlib/abort.c
@@ -19,6 +19,7 @@
 #include <internal-signals.h>
 #include <libc-lock.h>
 #include <pthreadP.h>
+#include <string.h>
 #include <unistd.h>
 
 /* Try to get a machine dependent instruction which will make the
@@ -42,7 +43,10 @@ __libc_rwlock_define_initialized (static, lock);
 void
 __abort_fork_reset_child (void)
 {
-  __libc_rwlock_init (lock);
+  /* Reinitialize lock without calling pthread_rwlock_init, to
+     avoid a valgrind DRD false positive.  */
+  __libc_rwlock_define_initialized (, reset_lock);
+  memcpy (&lock, &reset_lock, sizeof (lock));
 }
 
 void
-- 
2.50.1