devices: fs: Implement FS_IOC_FSSETXATTR

Needed by arcvm.

BUG=b:159297591
TEST=run a test program that calls the ioctl

Change-Id: I1f8c17fa2b2457f5a9e73045c3dbee3440eb943d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2265932
Auto-Submit: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>

devices/src/virtio/fs/passthrough.rs

@@ -64,6 +64,7 @@ struct fsxattr {
 unsafe impl DataInit for fsxattr {}
 
 ioctl_ior_nr!(FS_IOC_FSGETXATTR, 'X' as u32, 31, fsxattr);
+ioctl_iow_nr!(FS_IOC_FSSETXATTR, 'X' as u32, 32, fsxattr);
 
 type Inode = u64;
 type Handle = u64;
@@ -797,6 +798,26 @@ impl PassthroughFs {
             Ok(IoctlReply::Done(Ok(xattr.as_slice().to_vec())))
         }
     }
+
+    fn set_fsxattr<R: io::Read>(&self, handle: Handle, r: R) -> io::Result<IoctlReply> {
+        let data = self
+            .handles
+            .lock()
+            .get(&handle)
+            .map(Arc::clone)
+            .ok_or_else(ebadf)?;
+
+        let attr = fsxattr::from_reader(r)?;
+        let file = data.file.lock();
+
+        //  Safe because this doesn't modify any memory and we check the return value.
+        let res = unsafe { ioctl_with_ptr(&*file, FS_IOC_FSSETXATTR(), &attr) };
+        if res < 0 {
+            Ok(IoctlReply::Done(Err(io::Error::last_os_error())))
+        } else {
+            Ok(IoctlReply::Done(Ok(Vec::new())))
+        }
+    }
 }
 
 fn forget_one(
@@ -2011,6 +2032,7 @@ impl FileSystem for PassthroughFs {
         const GET_ENCRYPTION_POLICY: u32 = FS_IOC_GET_ENCRYPTION_POLICY() as u32;
         const SET_ENCRYPTION_POLICY: u32 = FS_IOC_SET_ENCRYPTION_POLICY() as u32;
         const GET_FSXATTR: u32 = FS_IOC_FSGETXATTR() as u32;
+        const SET_FSXATTR: u32 = FS_IOC_FSSETXATTR() as u32;
 
         // Normally, we wouldn't need to retry the FS_IOC_GET_ENCRYPTION_POLICY and
         // FS_IOC_SET_ENCRYPTION_POLICY ioctls. Unfortunately, the I/O directions for both of them
@@ -2047,6 +2069,13 @@ impl FileSystem for PassthroughFs {
                     self.get_fsxattr(handle)
                 }
             }
+            SET_FSXATTR => {
+                if in_size < size_of::<fsxattr>() as u32 {
+                    Err(io::Error::from_raw_os_error(libc::EINVAL))
+                } else {
+                    self.set_fsxattr(handle, r)
+                }
+            }
             _ => Err(io::Error::from_raw_os_error(libc::ENOTTY)),
         }
     }

seccomp/aarch64/fs_device.policy

@@ -22,7 +22,7 @@ ftruncate: 1
 getdents64: 1
 getegid: 1
 geteuid: 1
-ioctl: arg1 == FS_IOC_GET_ENCRYPTION_POLICY || arg1 == FS_IOC_SET_ENCRYPTION_POLICY || arg1 == FS_IOC_FSGETXATTR
+ioctl: arg1 == FS_IOC_GET_ENCRYPTION_POLICY || arg1 == FS_IOC_SET_ENCRYPTION_POLICY || arg1 == FS_IOC_FSGETXATTR || arg1 == FS_IOC_FSSETXATTR
 linkat: 1
 lseek: 1
 mkdirat: 1

seccomp/arm/fs_device.policy

@@ -22,7 +22,7 @@ ftruncate64: 1
 getdents64: 1
 getegid32: 1
 geteuid32: 1
-ioctl: arg1 == FS_IOC_GET_ENCRYPTION_POLICY || arg1 == FS_IOC_SET_ENCRYPTION_POLICY || arg1 == FS_IOC_FSGETXATTR
+ioctl: arg1 == FS_IOC_GET_ENCRYPTION_POLICY || arg1 == FS_IOC_SET_ENCRYPTION_POLICY || arg1 == FS_IOC_FSGETXATTR || arg1 == FS_IOC_FSSETXATTR
 linkat: 1
 _llseek: 1
 mkdir: 1

seccomp/x86_64/fs_device.policy

@@ -21,7 +21,7 @@ ftruncate: 1
 getdents64: 1
 getegid: 1
 geteuid: 1
-ioctl: arg1 == FS_IOC_GET_ENCRYPTION_POLICY || arg1 == FS_IOC_SET_ENCRYPTION_POLICY || arg1 == FS_IOC_FSGETXATTR
+ioctl: arg1 == FS_IOC_GET_ENCRYPTION_POLICY || arg1 == FS_IOC_SET_ENCRYPTION_POLICY || arg1 == FS_IOC_FSGETXATTR || arg1 == FS_IOC_FSSETXATTR
 linkat: 1
 lseek: 1
 mkdir: 1