| From 94225ab4bcc1613531558a632270b5edce779bc9 Mon Sep 17 00:00:00 2001 |
| From: Khem Raj <raj.khem@gmail.com> |
| Date: Sat, 27 Jan 2018 10:08:04 -0800 |
| Subject: [PATCH 27/27] Acquire ld.so lock before switching to malloc_atfork |
| |
| The patch is from |
| https://sourceware.org/bugzilla/show_bug.cgi?id=4578 |
| |
| If a thread happens to hold dl_load_lock and have r_state set to RT_ADD or |
| RT_DELETE at the time another thread calls fork(), then the child exit code |
| from fork (in nptl/sysdeps/unix/sysv/linux/fork.c in our case) re-initializes |
| dl_load_lock but does not restore r_state to RT_CONSISTENT. If the child |
| subsequently requires ld.so functionality before calling exec(), then the |
| assertion will fire. |
| |
| The patch acquires dl_load_lock on entry to fork() and releases it on exit |
| from the parent path. The child path is initialized as currently done. |
| This is essentially pthreads_atfork, but forced to be first because the |
| acquisition of dl_load_lock must happen before malloc_atfork is active |
| to avoid a deadlock. |
| |
| The patch has not yet been integrated upstream. |
| |
| Upstream-Status: Pending [ Not Author See bugzilla] |
| |
| Signed-off-by: Raghunath Lolur <Raghunath.Lolur@kpit.com> |
| Signed-off-by: Yuanjie Huang <yuanjie.huang@windriver.com> |
| Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com> |
| Signed-off-by: Khem Raj <raj.khem@gmail.com> |
| --- |
| sysdeps/nptl/fork.c | 9 +++++++++ |
| 1 file changed, 9 insertions(+) |
| |
| diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c |
| index f87506f398..225e7b51f8 100644 |
| --- a/sysdeps/nptl/fork.c |
| +++ b/sysdeps/nptl/fork.c |
| @@ -25,6 +25,7 @@ |
| #include <tls.h> |
| #include <hp-timing.h> |
| #include <ldsodefs.h> |
| +#include <libc-lock.h> |
| #include <stdio-lock.h> |
| #include <atomic.h> |
| #include <nptl/pthreadP.h> |
| @@ -60,6 +61,10 @@ __libc_fork (void) |
| but our current fork implementation is not. */ |
| bool multiple_threads = THREAD_GETMEM (THREAD_SELF, header.multiple_threads); |
| |
| + /* grab ld.so lock BEFORE switching to malloc_atfork */ |
| + __rtld_lock_lock_recursive (GL(dl_load_lock)); |
| + __rtld_lock_lock_recursive (GL(dl_load_write_lock)); |
| + |
| /* Run all the registered preparation handlers. In reverse order. |
| While doing this we build up a list of all the entries. */ |
| struct fork_handler *runp; |
| @@ -246,6 +251,10 @@ __libc_fork (void) |
| |
| allp = allp->next; |
| } |
| + |
| + /* unlock ld.so last, because we locked it first */ |
| + __rtld_lock_unlock_recursive (GL(dl_load_write_lock)); |
| + __rtld_lock_unlock_recursive (GL(dl_load_lock)); |
| } |
| |
| return pid; |
| -- |
| 2.16.1 |
| |