Merge branch 'net-rds-convert-rds-to-getsockopt_iter'

Breno Leitao says:

====================
net: rds: convert rds to getsockopt_iter

This series continues the conversion of the remaining proto_ops getsockopt
callbacks to the new getsockopt_iter callback introduced in commit
67fab22a7a ("net: add getsockopt_iter callback to proto_ops"), this time
for RDS.

RDS is a little more involved than the protocols converted so far, because
the RDS_INFO_* options snapshot kernel state directly into the destination
buffer: the info producers memcpy into the pages under a spinlock via
kmap_atomic() and so must not fault.

The conversion preserves that model — it obtains the same page array and
starting offset from opt->iter_out with iov_iter_extract_pages(),
preallocating the array so the iterator fills it in place, and leaves
the rds_info_iterator / rds_info_copy machinery and all producer
callbacks unchanged; kernel (ITER_KVEC) buffers remain unsupported on
the RDS_INFO path, as before.

I've vibe-coded a kselftest exercising both the simple options and the
RDS_INFO_* snapshot path, feel free to drop it in case this is not
useful.

Signed-off-by: Breno Leitao <leitao@debian.org>
====================

Link: https://patch.msgid.link/20260608-getsock_more-v3-0-706ecf2ea332@debian.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/rds/af_rds.c

@@ -37,6 +37,7 @@
 #include <linux/in.h>
 #include <linux/ipv6.h>
 #include <linux/poll.h>
+#include <linux/uio.h>
 #include <net/sock.h>
 
 #include "rds.h"
@@ -485,35 +486,36 @@ static int rds_setsockopt(struct socket *sock, int level, int optname,
 }
 
 static int rds_getsockopt(struct socket *sock, int level, int optname,
-			  char __user *optval, int __user *optlen)
+			  sockopt_t *opt)
 {
 	struct rds_sock *rs = rds_sk_to_rs(sock->sk);
 	int ret = -ENOPROTOOPT, len;
 	int trans;
+	int val;
 
 	if (level != SOL_RDS)
 		goto out;
 
-	if (get_user(len, optlen)) {
-		ret = -EFAULT;
-		goto out;
-	}
+	len = opt->optlen;
 
 	switch (optname) {
 	case RDS_INFO_FIRST ... RDS_INFO_LAST:
-		ret = rds_info_getsockopt(sock, optname, optval,
-					  optlen);
+		ret = rds_info_getsockopt(sock, optname, opt);
 		break;
 
 	case RDS_RECVERR:
-		if (len < sizeof(int))
+		if (len < sizeof(int)) {
 			ret = -EINVAL;
-		else
-		if (put_user(rs->rs_recverr, (int __user *) optval) ||
-		    put_user(sizeof(int), optlen))
+			break;
+		}
+		val = rs->rs_recverr;
+		if (copy_to_iter(&val, sizeof(int), &opt->iter_out) !=
+		    sizeof(int)) {
 			ret = -EFAULT;
-		else
+		} else {
+			opt->optlen = sizeof(int);
 			ret = 0;
+		}
 		break;
 	case SO_RDS_TRANSPORT:
 		if (len < sizeof(int)) {
@@ -522,11 +524,13 @@ static int rds_getsockopt(struct socket *sock, int level, int optname,
 		}
 		trans = (rs->rs_transport ? rs->rs_transport->t_type :
 			 RDS_TRANS_NONE); /* unbound */
-		if (put_user(trans, (int __user *)optval) ||
-		    put_user(sizeof(int), optlen))
+		if (copy_to_iter(&trans, sizeof(int), &opt->iter_out) !=
+		    sizeof(int)) {
 			ret = -EFAULT;
-		else
+		} else {
+			opt->optlen = sizeof(int);
 			ret = 0;
+		}
 		break;
 	default:
 		break;
@@ -653,7 +657,7 @@ static const struct proto_ops rds_proto_ops = {
 	.listen =	sock_no_listen,
 	.shutdown =	sock_no_shutdown,
 	.setsockopt =	rds_setsockopt,
-	.getsockopt =	rds_getsockopt,
+	.getsockopt_iter =	rds_getsockopt,
 	.sendmsg =	rds_sendmsg,
 	.recvmsg =	rds_recvmsg,
 	.mmap =		sock_no_mmap,

net/rds/info.c

@@ -35,6 +35,7 @@
 #include <linux/slab.h>
 #include <linux/proc_fs.h>
 #include <linux/export.h>
+#include <linux/uio.h>
 
 #include "rds.h"
 
@@ -144,39 +145,41 @@ void rds_info_copy(struct rds_info_iterator *iter, void *data,
 EXPORT_SYMBOL_GPL(rds_info_copy);
 
 /*
- * @optval points to the userspace buffer that the information snapshot
- * will be copied into.
- *
- * @optlen on input is the size of the buffer in userspace.  @optlen
- * on output is the size of the requested snapshot in bytes.
+ * @opt->iter_out describes the buffer that the information snapshot will be
+ * copied into, and @opt->optlen is the size of that buffer on input.  On
+ * output @opt->optlen is set to the size of the requested snapshot in bytes.
  *
  * This function returns -errno if there is a failure, particularly -ENOSPC
- * if the given userspace buffer was not large enough to fit the snapshot.
- * On success it returns the positive number of bytes of each array element
- * in the snapshot.
+ * if the given buffer was not large enough to fit the snapshot.  On success
+ * it returns the positive number of bytes of each array element in the
+ * snapshot.
  */
-int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
-			int __user *optlen)
+int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt)
 {
 	struct rds_info_iterator iter;
 	struct rds_info_lengths lens;
 	unsigned long nr_pages = 0;
-	unsigned long start;
 	rds_info_func func;
 	struct page **pages = NULL;
+	size_t offset0 = 0;
+	int npages = 0;
 	int ret;
 	int len;
 	int total;
 
-	if (get_user(len, optlen)) {
-		ret = -EFAULT;
+	len = opt->optlen;
+
+	/* check for all kinds of wrapping and the like */
+	if (len < 0 || len > INT_MAX - PAGE_SIZE + 1) {
+		ret = -EINVAL;
 		goto out;
 	}
 
-	/* check for all kinds of wrapping and the like */
-	start = (unsigned long)optval;
-	if (len < 0 || len > INT_MAX - PAGE_SIZE + 1 || start + len < start) {
-		ret = -EINVAL;
+	/* The info producers write into the pages with kmap_atomic() while
+	 * holding a spinlock, so they need a genuine page-backed user buffer.
+	 */
+	if (!user_backed_iter(&opt->iter_out)) {
+		ret = -EOPNOTSUPP;
 		goto out;
 	}
 
@@ -184,20 +187,26 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
 	if (len == 0)
 		goto call_func;
 
-	nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK))
-			>> PAGE_SHIFT;
-
-	pages = kmalloc_objs(struct page *, nr_pages);
+	/*
+	 * Preallocate the page array and pass it in so that
+	 * iov_iter_extract_pages() fills it in place rather than allocating
+	 * one for us.  Handing it a non-NULL array keeps ownership of the
+	 * array with us on every return path, instead of depending on the
+	 * iterator code to allocate and hand it back.
+	 */
+	npages = iov_iter_npages(&opt->iter_out, INT_MAX);
+	pages = kvmalloc_array(npages, sizeof(*pages), GFP_KERNEL);
 	if (!pages) {
 		ret = -ENOMEM;
 		goto out;
 	}
-	ret = pin_user_pages_fast(start, nr_pages, FOLL_WRITE, pages);
-	if (ret != nr_pages) {
-		if (ret > 0)
-			nr_pages = ret;
-		else
-			nr_pages = 0;
+
+	ret = iov_iter_extract_pages(&opt->iter_out, &pages, len, npages,
+				     0, &offset0);
+	if (ret < 0)
+		goto out;
+	nr_pages = DIV_ROUND_UP(offset0 + ret, PAGE_SIZE);
+	if (ret != len) {
 		ret = -EAGAIN; /* XXX ? */
 		goto out;
 	}
@@ -213,7 +222,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
 
 	iter.pages = pages;
 	iter.addr = NULL;
-	iter.offset = start & (PAGE_SIZE - 1);
+	iter.offset = offset0;
 
 	func(sock, len, &iter, &lens);
 	BUG_ON(lens.each == 0);
@@ -230,13 +239,16 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
 		ret = lens.each;
 	}
 
-	if (put_user(len, optlen))
-		ret = -EFAULT;
+	opt->optlen = len;
 
 out:
-	if (pages)
+	/*
+	 * iov_iter_extract_pages() pins only user-backed (ubuf) iters;
+	 * iov_iter_extract_will_pin() reports whether an unpin is owed here.
+	 */
+	if (pages && iov_iter_extract_will_pin(&opt->iter_out))
 		unpin_user_pages(pages, nr_pages);
-	kfree(pages);
+	kvfree(pages);
 
 	return ret;
 }

net/rds/info.h

@@ -21,8 +21,7 @@ typedef void (*rds_info_func)(struct socket *sock, unsigned int len,
 
 void rds_info_register_func(int optname, rds_info_func func);
 void rds_info_deregister_func(int optname, rds_info_func func);
-int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
-			int __user *optlen);
+int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt);
 void rds_info_copy(struct rds_info_iterator *iter, void *data,
 		   unsigned long bytes);
 void rds_info_iter_unmap(struct rds_info_iterator *iter);

tools/testing/selftests/net/rds/.gitignore

@@ -1 +1,2 @@
 include.sh
+getsockopt

tools/testing/selftests/net/rds/Makefile

@@ -5,6 +5,8 @@ all:
 
 TEST_PROGS := rds_run.sh
 
+TEST_GEN_PROGS := getsockopt
+
 TEST_FILES := \
 	include.sh \
 	settings \
@@ -16,4 +18,6 @@ EXTRA_CLEAN := \
 	/tmp/rds_logs \
 # end of EXTRA_CLEAN
 
+CFLAGS += $(KHDR_INCLUDES)
+
 include ../../lib.mk

tools/testing/selftests/net/rds/getsockopt.c

@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Exercise the RDS getsockopt() paths that were converted to the
+ * getsockopt_iter() / sockopt_t callback.
+ *
+ * Three distinct paths are covered:
+ *
+ *   - RDS_RECVERR and SO_RDS_TRANSPORT, which now return their int value
+ *     through copy_to_iter() and report the written length in opt->optlen.
+ *
+ *   - RDS_INFO_*, which pins the userspace buffer with
+ *     iov_iter_extract_pages() (including a non-zero starting page offset)
+ *     and lets the info producers memcpy the snapshot in under a spinlock.
+ *
+ * The kvec (in-kernel buffer) -> -EOPNOTSUPP path of rds_info_getsockopt()
+ * is not reachable from a userspace getsockopt() and so is not tested here.
+ */
+#include <errno.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/socket.h>
+#include <linux/rds.h>
+
+#include "../../kselftest_harness.h"
+
+#ifndef AF_RDS
+#define AF_RDS 21
+#endif
+
+FIXTURE(rds) {
+	int fd;
+};
+
+FIXTURE_SETUP(rds)
+{
+	self->fd = socket(AF_RDS, SOCK_SEQPACKET, 0);
+	if (self->fd < 0)
+		SKIP(return, "AF_RDS unavailable (errno %d) - load the rds module",
+		     errno);
+}
+
+FIXTURE_TEARDOWN(rds)
+{
+	if (self->fd >= 0)
+		close(self->fd);
+}
+
+/* RDS_RECVERR defaults to 0 and is reported back as a 4-byte int. */
+TEST_F(rds, recverr_default)
+{
+	socklen_t len = sizeof(int);
+	int val = 0xdeadbeef;
+
+	ASSERT_EQ(0, getsockopt(self->fd, SOL_RDS, RDS_RECVERR, &val, &len));
+	EXPECT_EQ(sizeof(int), len);
+	EXPECT_EQ(0, val);
+}
+
+/* A value set via setsockopt() must be readable back unchanged. */
+TEST_F(rds, recverr_set_get)
+{
+	socklen_t len = sizeof(int);
+	int val = 1;
+
+	ASSERT_EQ(0, setsockopt(self->fd, SOL_RDS, RDS_RECVERR, &val, len));
+
+	val = 0;
+	ASSERT_EQ(0, getsockopt(self->fd, SOL_RDS, RDS_RECVERR, &val, &len));
+	EXPECT_EQ(sizeof(int), len);
+	EXPECT_EQ(1, val);
+}
+
+/* A buffer smaller than an int is rejected with EINVAL, not silently. */
+TEST_F(rds, recverr_short_buffer)
+{
+	socklen_t len = sizeof(int) - 1;
+	char buf[sizeof(int)];
+
+	EXPECT_EQ(-1, getsockopt(self->fd, SOL_RDS, RDS_RECVERR, buf, &len));
+	EXPECT_EQ(EINVAL, errno);
+}
+
+/* An unbound socket reports RDS_TRANS_NONE for SO_RDS_TRANSPORT. */
+TEST_F(rds, transport_unbound)
+{
+	socklen_t len = sizeof(int);
+	int val = 0;
+
+	ASSERT_EQ(0, getsockopt(self->fd, SOL_RDS, SO_RDS_TRANSPORT, &val,
+				&len));
+	EXPECT_EQ(sizeof(int), len);
+	EXPECT_EQ(RDS_TRANS_NONE, (unsigned int)val);
+}
+
+TEST_F(rds, transport_short_buffer)
+{
+	socklen_t len = sizeof(int) - 1;
+	char buf[sizeof(int)];
+
+	EXPECT_EQ(-1, getsockopt(self->fd, SOL_RDS, SO_RDS_TRANSPORT, buf,
+				 &len));
+	EXPECT_EQ(EINVAL, errno);
+}
+
+/*
+ * RDS_INFO_COUNTERS with a zero-length buffer is the "probe" call: it must
+ * fail with ENOSPC and report the required snapshot size in optlen.
+ */
+TEST_F(rds, info_counters_probe)
+{
+	socklen_t len = 0;
+
+	EXPECT_EQ(-1, getsockopt(self->fd, SOL_RDS, RDS_INFO_COUNTERS, NULL,
+				 &len));
+	EXPECT_EQ(ENOSPC, errno);
+	EXPECT_GT(len, 0);
+	/* The snapshot is an array of fixed-size counter records. */
+	EXPECT_EQ(0, len % (socklen_t)sizeof(struct rds_info_counter));
+}
+
+/*
+ * A real snapshot into an unaligned userspace buffer exercises the
+ * iov_iter_extract_pages() path, including the non-zero offset0 handling
+ * that the patch reworked. Place the buffer at a non-page-aligned address
+ * spanning into the next page to make sure multi-page pinning works too.
+ */
+TEST_F(rds, info_counters_snapshot)
+{
+	struct rds_info_counter *ctr;
+	socklen_t need = 0, len;
+	long pagesz = sysconf(_SC_PAGESIZE);
+	size_t offset, map_len;
+	unsigned int i, n;
+	char *region, *buf;
+	int ret;
+
+	/* Probe for the required size. */
+	getsockopt(self->fd, SOL_RDS, RDS_INFO_COUNTERS, NULL, &need);
+	ASSERT_GT(need, 0);
+
+	/*
+	 * Place the buffer at a non-page-aligned offset that runs past the
+	 * first page boundary, and size the mapping from the probed length so
+	 * the test keeps working if the counter set grows.
+	 */
+	offset = pagesz - 64;
+	map_len = ((offset + need + pagesz - 1) / pagesz) * pagesz;
+
+	region = mmap(NULL, map_len, PROT_READ | PROT_WRITE,
+		      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	ASSERT_NE(MAP_FAILED, region);
+
+	buf = region + offset;
+
+	/*
+	 * On success the RDS_INFO path returns the positive per-element size
+	 * (lens.each) rather than 0, and writes the full snapshot length back
+	 * into optlen.
+	 */
+	len = need;
+	ret = getsockopt(self->fd, SOL_RDS, RDS_INFO_COUNTERS, buf, &len);
+	ASSERT_GE(ret, 0) {
+		TH_LOG("getsockopt snapshot failed: errno %d", errno);
+	}
+	EXPECT_EQ(sizeof(struct rds_info_counter), ret);
+	EXPECT_EQ(need, len);
+
+	/* The counter names must be NUL-terminated, non-empty strings. */
+	ctr = (struct rds_info_counter *)buf;
+	n = len / sizeof(*ctr);
+	ASSERT_GT(n, 0);
+	for (i = 0; i < n; i++) {
+		size_t namelen = strnlen((char *)ctr[i].name,
+					 sizeof(ctr[i].name));
+
+		EXPECT_GT(namelen, 0);
+		EXPECT_LT(namelen, sizeof(ctr[i].name));
+	}
+
+	munmap(region, map_len);
+}
+
+/*
+ * A non-zero but too-small buffer must report ENOSPC and the full required
+ * length, without corrupting memory past the buffer.
+ */
+TEST_F(rds, info_counters_short_buffer)
+{
+	socklen_t need = 0, len;
+	char small[sizeof(struct rds_info_counter)];
+
+	getsockopt(self->fd, SOL_RDS, RDS_INFO_COUNTERS, NULL, &need);
+	ASSERT_GT(need, 0);
+
+	/* Ask with a buffer guaranteed smaller than the full snapshot. */
+	if (need <= (socklen_t)sizeof(small))
+		SKIP(return, "snapshot fits in one record; nothing to test");
+
+	len = 1; /* < sizeof(struct rds_info_counter) */
+	EXPECT_EQ(-1, getsockopt(self->fd, SOL_RDS, RDS_INFO_COUNTERS, small,
+				 &len));
+	EXPECT_EQ(ENOSPC, errno);
+	EXPECT_EQ(need, len);
+}
+
+TEST_HARNESS_MAIN