fusefs: respect RLIMIT_FSIZE during truncate

PR:		164793
MFC after:	2 weeks
Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D36703

sys/fs/fuse/fuse_vnops.c

@@ -2248,6 +2248,9 @@ fuse_vnop_setattr(struct vop_setattr_args *ap)
 		case VREG:
 			if (vfs_isrdonly(mp))
 				return (EROFS);
+			err = vn_rlimit_trunc(vap->va_size, td);
+			if (err)
+				return (err);
 			break;
 		default:
 			/*

tests/sys/fs/fusefs/setattr.cc

@@ -31,22 +31,30 @@
  */
 
 extern "C" {
+#include <sys/types.h>
+#include <sys/resource.h>
 #include <sys/stat.h>
+#include <sys/time.h>
 
 #include <fcntl.h>
 #include <semaphore.h>
+#include <signal.h>
 }
 
 #include "mockfs.hh"
 #include "utils.hh"
 
 using namespace testing;
 
-class Setattr : public FuseTest {};
+class Setattr : public FuseTest {
+public:
+static sig_atomic_t s_sigxfsz;
+};
 
 class RofsSetattr: public Setattr {
 public:
 virtual void SetUp() {
+	s_sigxfsz = 0;
 	m_ro = true;
 	Setattr::SetUp();
 }
@@ -61,6 +69,12 @@ virtual void SetUp() {
 };
 
 
+sig_atomic_t Setattr::s_sigxfsz = 0;
+
+void sigxfsz_handler(int __unused sig) {
+	Setattr::s_sigxfsz = 1;
+}
+
 /*
  * If setattr returns a non-zero cache timeout, then subsequent VOP_GETATTRs
  * should use the cached attributes, rather than query the daemon
@@ -553,6 +567,34 @@ TEST_F(Setattr, truncate_discards_cached_data) {
 	leak(fd);
 }
 
+/* truncate should fail if it would cause the file to exceed RLIMIT_FSIZE */
+TEST_F(Setattr, truncate_rlimit_rsize)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	struct rlimit rl;
+	const uint64_t ino = 42;
+	const uint64_t oldsize = 0;
+	const uint64_t newsize = 100'000'000;
+
+	EXPECT_LOOKUP(FUSE_ROOT_ID, RELPATH)
+	.WillOnce(Invoke(ReturnImmediate([=](auto in __unused, auto& out) {
+		SET_OUT_HEADER_LEN(out, entry);
+		out.body.entry.attr.mode = S_IFREG | 0644;
+		out.body.entry.nodeid = ino;
+		out.body.entry.attr.size = oldsize;
+	})));
+
+	rl.rlim_cur = newsize / 2;
+	rl.rlim_max = 10 * newsize;
+	ASSERT_EQ(0, setrlimit(RLIMIT_FSIZE, &rl)) << strerror(errno);
+	ASSERT_NE(SIG_ERR, signal(SIGXFSZ, sigxfsz_handler)) << strerror(errno);
+
+	EXPECT_EQ(-1, truncate(FULLPATH, newsize));
+	EXPECT_EQ(EFBIG, errno);
+	EXPECT_EQ(1, s_sigxfsz);
+}
+
 /* Change a file's timestamps */
 TEST_F(Setattr, utimensat) {
 	const char FULLPATH[] = "mountpoint/some_file.txt";