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-rw-r--r--fs/inode.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/fs/inode.c b/fs/inode.c
index df6542ec3b88..8072a09fd0b9 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2170,3 +2170,27 @@ struct timespec64 current_time(struct inode *inode)
return timespec64_trunc(now, inode->i_sb->s_time_gran);
}
EXPORT_SYMBOL(current_time);
+
+/*
+ * Generic function to check FS_IOC_SETFLAGS values and reject any invalid
+ * configurations.
+ *
+ * Note: the caller should be holding i_mutex, or else be sure that they have
+ * exclusive access to the inode structure.
+ */
+int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags,
+ unsigned int flags)
+{
+ /*
+ * The IMMUTABLE and APPEND_ONLY flags can only be changed by
+ * the relevant capability.
+ *
+ * This test looks nicer. Thanks to Pauline Middelink
+ */
+ if ((flags ^ oldflags) & (FS_APPEND_FL | FS_IMMUTABLE_FL) &&
+ !capable(CAP_LINUX_IMMUTABLE))
+ return -EPERM;
+
+ return 0;
+}
+EXPORT_SYMBOL(vfs_ioc_setflags_prepare);