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* [newlib-cygwin] Cygwin: pipe: Fix race issue regarding handle count.
@ 2021-09-16 15:41 Ken Brown
0 siblings, 0 replies; only message in thread
From: Ken Brown @ 2021-09-16 15:41 UTC (permalink / raw)
To: cygwin-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=199482654b07e0603f668caaba8cddb2070cfdb8
commit 199482654b07e0603f668caaba8cddb2070cfdb8
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Thu Sep 16 23:21:57 2021 +0900
Cygwin: pipe: Fix race issue regarding handle count.
- This patch fixes the race issue in the handle counting to detect
closure of read pipe, which is introduced by commit f79a4611.
A mutex hdl_cnt_mtx is introduced for this issue.
Diff:
---
winsup/cygwin/fhandler.h | 1 +
winsup/cygwin/fhandler_pipe.cc | 65 ++++++++++++++++++++++++++++++++++++++----
2 files changed, 60 insertions(+), 6 deletions(-)
diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index eb312ccb6..31edb1822 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1176,6 +1176,7 @@ class fhandler_pipe_fifo: public fhandler_base
protected:
size_t pipe_buf_size;
HANDLE query_hdl;
+ HANDLE hdl_cnt_mtx;
virtual void release_select_sem (const char *) {};
public:
diff --git a/winsup/cygwin/fhandler_pipe.cc b/winsup/cygwin/fhandler_pipe.cc
index 582b4d564..2068a943e 100644
--- a/winsup/cygwin/fhandler_pipe.cc
+++ b/winsup/cygwin/fhandler_pipe.cc
@@ -200,7 +200,14 @@ fhandler_pipe::open_setup (int flags)
SECURITY_ATTRIBUTES *sa = sec_none_cloexec (flags);
read_mtx = CreateMutex (sa, FALSE, NULL);
if (!read_mtx)
- debug_printf ("CreateMutex failed: %E");
+ debug_printf ("CreateMutex read_mtx failed: %E");
+ }
+ if (!hdl_cnt_mtx)
+ {
+ SECURITY_ATTRIBUTES *sa = sec_none_cloexec (flags);
+ hdl_cnt_mtx = CreateMutex (sa, FALSE, NULL);
+ if (!hdl_cnt_mtx)
+ debug_printf ("CreateMutex hdl_cnt_mtx failed: %E");
}
if (get_dev () == FH_PIPEW && !query_hdl)
set_pipe_non_blocking (is_nonblocking ());
@@ -390,8 +397,12 @@ fhandler_pipe_fifo::reader_closed ()
{
if (!query_hdl)
return false;
+ if (hdl_cnt_mtx)
+ WaitForSingleObject (hdl_cnt_mtx, INFINITE);
int n_reader = get_obj_handle_count (query_hdl);
int n_writer = get_obj_handle_count (get_handle ());
+ if (hdl_cnt_mtx)
+ ReleaseMutex (hdl_cnt_mtx);
return n_reader == n_writer;
}
@@ -554,11 +565,18 @@ fhandler_pipe::set_close_on_exec (bool val)
set_no_inheritance (select_sem, val);
if (query_hdl)
set_no_inheritance (query_hdl, val);
+ if (hdl_cnt_mtx)
+ set_no_inheritance (hdl_cnt_mtx, val);
}
void
fhandler_pipe::fixup_after_fork (HANDLE parent)
{
+ if (hdl_cnt_mtx)
+ {
+ fork_fixup (parent, hdl_cnt_mtx, "hdl_cnt_mtx");
+ WaitForSingleObject (hdl_cnt_mtx, INFINITE);
+ }
if (read_mtx)
fork_fixup (parent, read_mtx, "read_mtx");
if (select_sem)
@@ -567,6 +585,8 @@ fhandler_pipe::fixup_after_fork (HANDLE parent)
fork_fixup (parent, query_hdl, "query_hdl");
fhandler_base::fixup_after_fork (parent);
+ if (hdl_cnt_mtx)
+ ReleaseMutex (hdl_cnt_mtx);
}
int
@@ -576,6 +596,8 @@ fhandler_pipe::dup (fhandler_base *child, int flags)
ftp->set_popen_pid (0);
int res = 0;
+ if (hdl_cnt_mtx)
+ WaitForSingleObject (hdl_cnt_mtx, INFINITE);
if (fhandler_base::dup (child, flags))
res = -1;
else if (read_mtx &&
@@ -589,8 +611,8 @@ fhandler_pipe::dup (fhandler_base *child, int flags)
}
else if (select_sem &&
!DuplicateHandle (GetCurrentProcess (), select_sem,
- GetCurrentProcess (), &ftp->select_sem,
- 0, !(flags & O_CLOEXEC), DUPLICATE_SAME_ACCESS))
+ GetCurrentProcess (), &ftp->select_sem,
+ 0, !(flags & O_CLOEXEC), DUPLICATE_SAME_ACCESS))
{
__seterrno ();
ftp->close ();
@@ -598,13 +620,24 @@ fhandler_pipe::dup (fhandler_base *child, int flags)
}
else if (query_hdl &&
!DuplicateHandle (GetCurrentProcess (), query_hdl,
- GetCurrentProcess (), &ftp->query_hdl,
- 0, !(flags & O_CLOEXEC), DUPLICATE_SAME_ACCESS))
+ GetCurrentProcess (), &ftp->query_hdl,
+ 0, !(flags & O_CLOEXEC), DUPLICATE_SAME_ACCESS))
+ {
+ __seterrno ();
+ ftp->close ();
+ res = -1;
+ }
+ else if (hdl_cnt_mtx &&
+ !DuplicateHandle (GetCurrentProcess (), hdl_cnt_mtx,
+ GetCurrentProcess (), &ftp->hdl_cnt_mtx,
+ 0, !(flags & O_CLOEXEC), DUPLICATE_SAME_ACCESS))
{
__seterrno ();
ftp->close ();
res = -1;
}
+ if (hdl_cnt_mtx)
+ ReleaseMutex (hdl_cnt_mtx);
debug_printf ("res %d", res);
return res;
@@ -620,9 +653,17 @@ fhandler_pipe::close ()
}
if (read_mtx)
CloseHandle (read_mtx);
+ if (hdl_cnt_mtx)
+ WaitForSingleObject (hdl_cnt_mtx, INFINITE);
if (query_hdl)
CloseHandle (query_hdl);
- return fhandler_base::close ();
+ int ret = fhandler_base::close ();
+ if (hdl_cnt_mtx)
+ {
+ ReleaseMutex (hdl_cnt_mtx);
+ CloseHandle (hdl_cnt_mtx);
+ }
+ return ret;
}
#define PIPE_INTRO "\\\\.\\pipe\\cygwin-"
@@ -834,9 +875,21 @@ fhandler_pipe::create (fhandler_pipe *fhs[2], unsigned psize, int mode)
FILE_READ_DATA, sa->bInheritHandle, 0))
goto err_close_select_sem1;
+ fhs[0]->hdl_cnt_mtx = CreateMutexW (sa, FALSE, NULL);
+ if (!fhs[0]->hdl_cnt_mtx)
+ goto err_close_query_hdl;
+ if (!DuplicateHandle (GetCurrentProcess (), fhs[0]->hdl_cnt_mtx,
+ GetCurrentProcess (), &fhs[1]->hdl_cnt_mtx,
+ 0, sa->bInheritHandle, DUPLICATE_SAME_ACCESS))
+ goto err_close_hdl_cnt_mtx0;
+
res = 0;
goto out;
+err_close_hdl_cnt_mtx0:
+ CloseHandle (fhs[0]->hdl_cnt_mtx);
+err_close_query_hdl:
+ CloseHandle (fhs[1]->query_hdl);
err_close_select_sem1:
CloseHandle (fhs[1]->select_sem);
err_close_select_sem0:
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2021-09-16 15:41 [newlib-cygwin] Cygwin: pipe: Fix race issue regarding handle count Ken Brown
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