157 lines
5.6 KiB
Diff
157 lines
5.6 KiB
Diff
From c096b008d2671028c21ac8cf01f18a2083e73c44 Mon Sep 17 00:00:00 2001
|
|
From: Florian Weimer <fweimer@redhat.com>
|
|
Date: Fri, 8 Feb 2019 12:54:41 +0100
|
|
Subject: [PATCH 05] nptl: Avoid fork handler lock for async-signal-safe
|
|
fork [BZ #24161]
|
|
|
|
Commit 27761a1042daf01987e7d79636d0c41511c6df3c ("Refactor atfork
|
|
handlers") introduced a lock, atfork_lock, around fork handler list
|
|
accesses. It turns out that this lock occasionally results in
|
|
self-deadlocks in malloc/tst-mallocfork2:
|
|
|
|
(gdb) bt
|
|
#0 __lll_lock_wait_private ()
|
|
at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:63
|
|
#1 0x00007f160c6f927a in __run_fork_handlers (who=(unknown: 209394016),
|
|
who@entry=atfork_run_prepare) at register-atfork.c:116
|
|
#2 0x00007f160c6b7897 in __libc_fork () at ../sysdeps/nptl/fork.c:58
|
|
#3 0x00000000004027d6 in sigusr1_handler (signo=<optimized out>)
|
|
at tst-mallocfork2.c:80
|
|
#4 sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:64
|
|
#5 <signal handler called>
|
|
#6 0x00007f160c6f92e4 in __run_fork_handlers (who=who@entry=atfork_run_parent)
|
|
at register-atfork.c:136
|
|
#7 0x00007f160c6b79a2 in __libc_fork () at ../sysdeps/nptl/fork.c:152
|
|
#8 0x0000000000402567 in do_test () at tst-mallocfork2.c:156
|
|
#9 0x0000000000402dd2 in support_test_main (argc=1, argv=0x7ffc81ef1ab0,
|
|
config=config@entry=0x7ffc81ef1970) at support_test_main.c:350
|
|
#10 0x0000000000402362 in main (argc=<optimized out>, argv=<optimized out>)
|
|
at ../support/test-driver.c:168
|
|
|
|
If no locking happens in the single-threaded case (where fork is
|
|
expected to be async-signal-safe), this deadlock is avoided.
|
|
(pthread_atfork is not required to be async-signal-safe, so a fork
|
|
call from a signal handler interrupting pthread_atfork is not
|
|
a problem.)
|
|
|
|
(cherry picked from commit 669ff911e2571f74a2668493e326ac9a505776bd)
|
|
---
|
|
ChangeLog | 10 ++++++++++
|
|
NEWS | 1 +
|
|
nptl/register-atfork.c | 8 +++++---
|
|
sysdeps/nptl/fork.c | 6 +++---
|
|
sysdeps/nptl/fork.h | 8 +++++---
|
|
5 files changed, 24 insertions(+), 9 deletions(-)
|
|
|
|
diff --git a/ChangeLog b/ChangeLog
|
|
index 7a8895bcc6..d363be4620 100644
|
|
--- a/ChangeLog
|
|
+++ b/ChangeLog
|
|
@@ -1,3 +1,13 @@
|
|
+2019-02-08 Florian Weimer <fweimer@redhat.com>
|
|
+
|
|
+ [BZ #24161]
|
|
+ * sysdeps/nptl/fork.h (__run_fork_handlers): Add multiple_threads
|
|
+ argument.
|
|
+ * nptl/register-atfork.c (__run_fork_handlers): Only perform
|
|
+ locking if the new do_locking argument is true.
|
|
+ * sysdeps/nptl/fork.c (__libc_fork): Pass multiple_threads to
|
|
+ __run_fork_handlers.
|
|
+
|
|
2019-02-07 Stefan Liebler <stli@linux.ibm.com>
|
|
|
|
[BZ #24180]
|
|
diff --git a/NEWS b/NEWS
|
|
index 1f0fc4b3cb..dbcdd48502 100644
|
|
--- a/NEWS
|
|
+++ b/NEWS
|
|
@@ -11,6 +11,7 @@ The following bugs are resolved with this release:
|
|
|
|
[24155] x32 memcmp can treat positive length as 0 (if sign bit in RDX is set) (CVE-2019-7309)
|
|
[24164] Systemtap probes need to use "nr" constraint on 32-bit Arm
|
|
+ [24161] __run_fork_handlers self-deadlocks in malloc/tst-mallocfork2
|
|
|
|
Security related changes:
|
|
|
|
diff --git a/nptl/register-atfork.c b/nptl/register-atfork.c
|
|
index bc797b761a..80a1becb5f 100644
|
|
--- a/nptl/register-atfork.c
|
|
+++ b/nptl/register-atfork.c
|
|
@@ -107,13 +107,14 @@ __unregister_atfork (void *dso_handle)
|
|
}
|
|
|
|
void
|
|
-__run_fork_handlers (enum __run_fork_handler_type who)
|
|
+__run_fork_handlers (enum __run_fork_handler_type who, _Bool do_locking)
|
|
{
|
|
struct fork_handler *runp;
|
|
|
|
if (who == atfork_run_prepare)
|
|
{
|
|
- lll_lock (atfork_lock, LLL_PRIVATE);
|
|
+ if (do_locking)
|
|
+ lll_lock (atfork_lock, LLL_PRIVATE);
|
|
size_t sl = fork_handler_list_size (&fork_handlers);
|
|
for (size_t i = sl; i > 0; i--)
|
|
{
|
|
@@ -133,7 +134,8 @@ __run_fork_handlers (enum __run_fork_handler_type who)
|
|
else if (who == atfork_run_parent && runp->parent_handler)
|
|
runp->parent_handler ();
|
|
}
|
|
- lll_unlock (atfork_lock, LLL_PRIVATE);
|
|
+ if (do_locking)
|
|
+ lll_unlock (atfork_lock, LLL_PRIVATE);
|
|
}
|
|
}
|
|
|
|
diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c
|
|
index bd68f18b45..14b69a6f89 100644
|
|
--- a/sysdeps/nptl/fork.c
|
|
+++ b/sysdeps/nptl/fork.c
|
|
@@ -55,7 +55,7 @@ __libc_fork (void)
|
|
but our current fork implementation is not. */
|
|
bool multiple_threads = THREAD_GETMEM (THREAD_SELF, header.multiple_threads);
|
|
|
|
- __run_fork_handlers (atfork_run_prepare);
|
|
+ __run_fork_handlers (atfork_run_prepare, multiple_threads);
|
|
|
|
/* If we are not running multiple threads, we do not have to
|
|
preserve lock state. If fork runs from a signal handler, only
|
|
@@ -134,7 +134,7 @@ __libc_fork (void)
|
|
__rtld_lock_initialize (GL(dl_load_lock));
|
|
|
|
/* Run the handlers registered for the child. */
|
|
- __run_fork_handlers (atfork_run_child);
|
|
+ __run_fork_handlers (atfork_run_child, multiple_threads);
|
|
}
|
|
else
|
|
{
|
|
@@ -149,7 +149,7 @@ __libc_fork (void)
|
|
}
|
|
|
|
/* Run the handlers registered for the parent. */
|
|
- __run_fork_handlers (atfork_run_parent);
|
|
+ __run_fork_handlers (atfork_run_parent, multiple_threads);
|
|
}
|
|
|
|
return pid;
|
|
diff --git a/sysdeps/nptl/fork.h b/sysdeps/nptl/fork.h
|
|
index a1c3b26b68..99ed76034b 100644
|
|
--- a/sysdeps/nptl/fork.h
|
|
+++ b/sysdeps/nptl/fork.h
|
|
@@ -52,9 +52,11 @@ enum __run_fork_handler_type
|
|
- atfork_run_child: run all the CHILD_HANDLER and unlocks the internal
|
|
lock.
|
|
- atfork_run_parent: run all the PARENT_HANDLER and unlocks the internal
|
|
- lock. */
|
|
-extern void __run_fork_handlers (enum __run_fork_handler_type who)
|
|
- attribute_hidden;
|
|
+ lock.
|
|
+
|
|
+ Perform locking only if DO_LOCKING. */
|
|
+extern void __run_fork_handlers (enum __run_fork_handler_type who,
|
|
+ _Bool do_locking) attribute_hidden;
|
|
|
|
/* C library side function to register new fork handlers. */
|
|
extern int __register_atfork (void (*__prepare) (void),
|
|
|