1 files changed, 17 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 4f476411a9a2..440922a7d8f1 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -4376,6 +4376,20 @@ resched:
 }
 
 /*
+ * See mincore: reveal pagecache information only for files
+ * that the calling process has write access to, or could (if
+ * tried) open for writing.
+ */
+static inline bool can_do_cachestat(struct file *f)
+{
+	if (f->f_mode & FMODE_WRITE)
+		return true;
+	if (inode_owner_or_capable(file_mnt_idmap(f), file_inode(f)))
+		return true;
+	return file_permission(f, MAY_WRITE) == 0;
+}
+
+/*
  * The cachestat(2) system call.
  *
  * cachestat() returns the page cache statistics of a file in the
@@ -4430,6 +4444,9 @@ SYSCALL_DEFINE4(cachestat, unsigned int, fd,
 	if (is_file_hugepages(fd_file(f)))
 		return -EOPNOTSUPP;
 
+	if (!can_do_cachestat(fd_file(f)))
+		return -EPERM;
+
 	if (flags != 0)
 		return -EINVAL;