OBS-URL: https://build.opensuse.org/package/show/Base:System/libcap?expand=0&rev=44

2020-11-15 16:29:16 +00:00 · 2020-11-15 16:29:16 +00:00 · 37271ea66e
commit 37271ea66e
parent 94f4e5b306
4 changed files with 123 additions and 5 deletions
--- a/0001-Allow-a-dying-thread-to-participate-in-the-psx-mecha.patch
+++ b/0001-Allow-a-dying-thread-to-participate-in-the-psx-mecha.patch
@ -0,0 +1,114 @@
+From 7cfe15ee579ea83a7780c6190576fdcab3e2faac Mon Sep 17 00:00:00 2001
+From: "Andrew G. Morgan" <morgan@kernel.org>
+Date: Wed, 11 Nov 2020 19:53:06 -0800
+Subject: [PATCH] Allow a dying thread to participate in the psx mechanism.
+
+If a dying thread blocks all interrupts in order to die in peace,
+it can deadlock the psx mechanism for all the surviving threads.
+To account for this corner case, while waiting to enter the
+_PSX_EXITING state, temporarily unblock the psx_tracker.psx_sig.
+
+  https://github.com/golang/go/issues/42494
+
+Add a psx_test.go:TestThreadChurn() test case for this issue.
+
+Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
+---
+ psx/psx.c       | 34 ++++++++++++++++++++++++++++++++++
+ psx/psx_test.go | 33 +++++++++++++++++++++++++++++++++
+ 2 files changed, 67 insertions(+)
+
+diff --git a/psx/psx.c b/psx/psx.c
+index 72c2098..233267d 100644
+--- a/psx/psx.c
+++ b/psx/psx.c
+@@ -336,11 +336,45 @@ typedef struct {
+  *    https://sourceware.org/bugzilla/show_bug.cgi?id=12889
+  */
+ static void _psx_exiting(void *node) {
+    /*
+     * Until we are in the _PSX_EXITING state, we must not block the
+     * psx_sig interrupt for this dying thread. That is, until this
+     * exiting thread can set ref->gone to 1, this dying thread is
+     * still participating in the psx syscall distribution.
+     *
+     * See https://github.com/golang/go/issues/42494 for a situation
+     * where this code is called with psx_tracker.psx_sig blocked.
+     */
+    sigset_t sigbit, orig_sigbits;
+    sigemptyset(&sigbit);
+    pthread_sigmask(SIG_UNBLOCK, &sigbit, &orig_sigbits);
+    sigaddset(&sigbit, psx_tracker.psx_sig);
+    pthread_sigmask(SIG_UNBLOCK, &sigbit, NULL);
+
+    /*
+     * With psx_tracker.psx_sig unblocked we can wait until this
+     * thread can enter the _PSX_EXITING state.
+     */
+     psx_new_state(_PSX_IDLE, _PSX_EXITING);
+
+    /*
+     * We now indicate that this thread is no longer participating in
+     * the psx mechanism.
+     */
+     registered_thread_t *ref = node;
+     pthread_mutex_lock(&ref->mu);
+     ref->gone = 1;
+     pthread_mutex_unlock(&ref->mu);
+
+    /*
+     * At this point, we can restore the calling sigmask to whatever
+     * the caller thought was appropriate for a dying thread to have.
+     */
+    pthread_sigmask(SIG_SETMASK, &orig_sigbits, NULL);
+
+    /*
+     * Allow the rest of the psx system carry on as per normal.
+     */
+     psx_new_state(_PSX_EXITING, _PSX_IDLE);
+ }
+ 
+diff --git a/psx/psx_test.go b/psx/psx_test.go
+index ae6ccd2..3f0445c 100644
+--- a/psx/psx_test.go
+++ b/psx/psx_test.go
+@@ -64,3 +64,36 @@ func TestErrno(t *testing.T) {
+ 		t.Errorf("psx changes prevailing errno got=%v(%d) want=%v", syscall.Errno(v), v, syscall.EPERM)
+ 	}
+ }
+
+// killAThread locks the goroutine to a thread and exits. This has the
+// effect of making the go runtime terminate the thread.
+func killAThread(c <-chan struct{}) {
+	runtime.LockOSThread()
+	<-c
+}
+
+// Test to confirm no regression against:
+//
+//   https://github.com/golang/go/issues/42494
+func TestThreadChurn(t *testing.T) {
+	const prSetKeepCaps = 8
+
+	for j := 0; j < 4; j++ {
+		kill := (j & 1) != 0
+		sysc := (j & 2) != 0
+		t.Logf("[%d] testing kill=%v, sysc=%v", j, kill, sysc)
+		for i := 50; i > 0; i-- {
+			if kill {
+				c := make(chan struct{})
+				go killAThread(c)
+				close(c)
+			}
+			if sysc {
+				if _, _, e := Syscall3(syscall.SYS_PRCTL, prSetKeepCaps, uintptr(i&1), 0); e != 0 {
+					t.Fatalf("[%d] psx:prctl(SET_KEEPCAPS, %d) failed: %v", i, i&1, syscall.Errno(e))
+				}
+			}
+		}
+		t.Logf("[%d] PASSED kill=%v, sysc=%v", j, kill, sysc)
+	}
+}
+-- 
+2.29.2
+
--- a/libcap-2.44.tar.xz
+++ b/libcap-2.44.tar.xz
@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:92188359cd5be86e8e5bd3f6483ac6ce582264f912398937ef763def2205c8e1
+size 125568
--- a/libcap-2.45.tar.xz
+++ b/libcap-2.45.tar.xz
@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:d66639f765c0e10557666b00f519caf0bd07a95f867dddaee131cd284fac3286
-size 127608
--- a/libcap.spec
+++ b/libcap.spec
@ -17,7 +17,7 @@


 Name:           libcap
-Version:        2.45
+Version:        2.44
 Release:        0
 Summary:        Library for Capabilities (linux-privs) Support
 License:        BSD-3-Clause AND GPL-2.0-only
@ -25,6 +25,7 @@ Group:          Development/Libraries/C and C++
 URL:            https://sites.google.com/site/fullycapable/
 Source:         https://www.kernel.org/pub/linux/libs/security/linux-privs/libcap2/libcap-%{version}.tar.xz
 Source2:        baselibs.conf
+Patch:          0001-Allow-a-dying-thread-to-participate-in-the-psx-mecha.patch
 BuildRequires:  fdupes
 BuildRequires:  glibc-devel-static
 BuildRequires:  pkgconfig
@ -89,11 +90,12 @@ libcap.

 %prep
 %setup -q
+%patch -p1

 %build
 %global _lto_cflags %{_lto_cflags} -ffat-lto-objects
 make prefix=%{_prefix} lib=%{_lib} LIBDIR=%{_libdir} SBINDIR=%{_sbindir} \
-     INCDIR=%{_includedir} MANDIR=%{_mandir} DYNAMIC=yes DEBUG="-g %{optflags}"
+     INCDIR=%{_includedir} MANDIR=%{_mandir} SHARED=yes DEBUG="-g %{optflags}"

 %install
 make install RAISE_SETFCAP=no \
@ -115,12 +117,14 @@ make test
 %post -n libcap2 -p /sbin/ldconfig
 %postun -n libcap2 -p /sbin/ldconfig

+%ifarch aarch64
 %post -n libpsx2 -p /sbin/ldconfig
 %postun -n libpsx2 -p /sbin/ldconfig

 %files -n libpsx2
 %license License
 %{_libdir}/libpsx.so.2*
+%endif

 %files -n libcap2
 %license License