From 2b41ddf343e8e314dc60fae0d5f4e007ce3857e4 Mon Sep 17 00:00:00 2001
From: Patrick Donnelly <pdonnell@redhat.com>
Date: Wed, 11 Nov 2020 11:29:12 -0800
Subject: [PATCH 1/2] test/libcephfs: test truncate on rdonly fd

Fixes: https://tracker.ceph.com/issues/48202
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
---
 src/test/libcephfs/test.cc | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/test/libcephfs/test.cc b/src/test/libcephfs/test.cc
index dc4e627eeee..ef43e108705 100644
--- a/src/test/libcephfs/test.cc
+++ b/src/test/libcephfs/test.cc
@@ -33,6 +33,7 @@
 #include <sys/xattr.h>
 #endif
 
+#include <fmt/format.h>
 #include <map>
 #include <vector>
 #include <thread>
@@ -80,6 +81,30 @@ TEST(LibCephFS, OpenEmptyComponent) {
   ceph_shutdown(cmount);
 }
 
+TEST(LibCephFS, OpenReadTruncate) {
+  struct ceph_mount_info *cmount;
+  ASSERT_EQ(0, ceph_create(&cmount, NULL));
+  ASSERT_EQ(0, ceph_conf_read_file(cmount, NULL));
+  ASSERT_EQ(0, ceph_conf_parse_env(cmount, NULL));
+  ASSERT_EQ(0, ceph_mount(cmount, "/"));
+
+  auto path = fmt::format("test_open_rdt_{}", getpid());
+  int fd = ceph_open(cmount, path.c_str(), O_WRONLY|O_CREAT, 0666);
+  ASSERT_LE(0, fd);
+
+  auto data = std::string("hello world");
+  ASSERT_EQ(ceph_write(cmount, fd, data.c_str(), data.size(), 0), (int)data.size());
+  ASSERT_EQ(0, ceph_close(cmount, fd));
+
+  fd = ceph_open(cmount, path.c_str(), O_RDONLY, 0);
+  ASSERT_LE(0, fd);
+  ASSERT_EQ(ceph_ftruncate(cmount, fd, 0), -EBADF);
+  ASSERT_EQ(ceph_ftruncate(cmount, fd, 1), -EBADF);
+  ASSERT_EQ(0, ceph_close(cmount, fd));
+
+  ceph_shutdown(cmount);
+}
+
 TEST(LibCephFS, OpenReadWrite) {
   struct ceph_mount_info *cmount;
   ASSERT_EQ(0, ceph_create(&cmount, NULL));

From 3bb209772eada4ba5010be521f7ecaae567598d0 Mon Sep 17 00:00:00 2001
From: Patrick Donnelly <pdonnell@redhat.com>
Date: Wed, 11 Nov 2020 11:37:09 -0800
Subject: [PATCH 2/2] client: check rdonly file handle on truncate

Fixes: https://tracker.ceph.com/issues/48202
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
---
 src/client/Client.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/client/Client.cc b/src/client/Client.cc
index 35dbd94058c..12cd6c741fb 100644
--- a/src/client/Client.cc
+++ b/src/client/Client.cc
@@ -10134,6 +10134,8 @@ int Client::ftruncate(int fd, loff_t length, const UserPerm& perms)
   if (f->flags & O_PATH)
     return -EBADF;
 #endif
+  if ((f->mode & CEPH_FILE_MODE_WR) == 0)
+    return -EBADF;
   struct stat attr;
   attr.st_size = length;
   return _setattr(f->inode, &attr, CEPH_SETATTR_SIZE, perms);