debug: make __read_chk a cancellation point (bug 29274)

The __read_chk function, as the implementation behind the fortified read
function, must be a cancellation point, thus it cannot use INLINE_SYSCALL.

3 files changed, 57 insertions, 10 deletions

diff --git a/debug/Makefile b/debug/Makefile
index 96029f3..456b349 100644
--- a/debug/Makefile
+++ b/debug/Makefile
@@ -110,6 +110,7 @@ CPPFLAGS-tst-longjmp_chk2.c += -D_FORTIFY_SOURCE=1
 CFLAGS-tst-longjmp_chk3.c += -fexceptions -fasynchronous-unwind-tables
 CPPFLAGS-tst-longjmp_chk3.c += -D_FORTIFY_SOURCE=1
 CPPFLAGS-tst-realpath-chk.c += -D_FORTIFY_SOURCE=2
+CPPFLAGS-tst-read-chk-cancel.c += -D_FORTIFY_SOURCE=2
 
 # _FORTIFY_SOURCE tests.
 # Auto-generate tests for _FORTIFY_SOURCE for different levels, compilers and
@@ -204,6 +205,10 @@ ifeq ($(have-ssp),yes)
 tests += tst-ssp-1
 endif
 
+ifeq ($(have-thread-library), yes)
+tests += tst-read-chk-cancel
+endif
+
 ifeq (,$(CXX))
 tests-unsupported = $(tests-cc-chk)
 endif
@@ -242,3 +247,5 @@ $(objpfx)xtrace: xtrace.sh
 	    -e 's|@BINDIR@|$(bindir)|' -e 's|@PKGVERSION@|$(PKGVERSION)|' \
 	    -e 's|@REPORT_BUGS_TO@|$(REPORT_BUGS_TO)|' $^ > $@.new \
 	&& rm -f $@ && mv $@.new $@ && chmod +x $@
+
+$(objpfx)tst-read-chk-cancel: $(shared-thread-library)
diff --git a/debug/read_chk.c b/debug/read_chk.c
index 0cd58db..274b4f9 100644
--- a/debug/read_chk.c
+++ b/debug/read_chk.c
@@ -16,12 +16,6 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <unistd.h>
-#include <sys/param.h>
-#ifdef HAVE_INLINED_SYSCALLS
-# include <errno.h>
-# include <sysdep.h>
-#endif
-
 
 ssize_t
 __read_chk (int fd, void *buf, size_t nbytes, size_t buflen)
@@ -29,9 +23,5 @@ __read_chk (int fd, void *buf, size_t nbytes, size_t buflen)
   if (nbytes > buflen)
     __chk_fail ();
 
-#ifdef HAVE_INLINED_SYSCALLS
-  return INLINE_SYSCALL (read, 3, fd, buf, nbytes);
-#else
   return __read (fd, buf, nbytes);
-#endif
 }
diff --git a/debug/tst-read-chk-cancel.c b/debug/tst-read-chk-cancel.c
new file mode 100644
index 0000000..7e06afb
--- /dev/null
+++ b/debug/tst-read-chk-cancel.c
@@ -0,0 +1,50 @@
+/* Test that __read_chk is a cancellation point (BZ #29274)
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdint.h>
+#include <support/xunistd.h>
+#include <support/xthread.h>
+
+static int pipe_fds[2];
+static pthread_barrier_t barrier;
+
+static void *
+read_thread (void *n)
+{
+  xpthread_barrier_wait (&barrier);
+  char c;
+  /* This call should be forwarded to __read_chk because the buffer size
+     is known, but the read length is non-constant.  */
+  if (read (pipe_fds[0], &c, (uintptr_t) n) != 1)
+    return (void *) -1L;
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  xpthread_barrier_init (&barrier, 0, 2);
+  xpipe (pipe_fds);
+  pthread_t thr = xpthread_create (0, read_thread, (void *) 1L);
+  xpthread_barrier_wait (&barrier);
+  xpthread_cancel (thr);
+  xpthread_join (thr);
+  return 0;
+}
+
+#include <support/test-driver.c>