Remove suid/sgid bits on [f]truncate()

.. to match what we do on write().  This way, people who write to files
by using [f]truncate + writable mmap have the same semantics as if they
were using the write() family of system calls.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/open.c b/fs/open.c
index ca9981c4a658..0d515d161974 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -210,6 +210,9 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
                 newattrs.ia_valid |= ATTR_FILE;
         }
 
+        /* Remove suid/sgid on truncate too */
+        newattrs.ia_valid |= should_remove_suid(dentry);
+
         mutex_lock(&dentry->d_inode->i_mutex);
         err = notify_change(dentry, &newattrs);
         mutex_unlock(&dentry->d_inode->i_mutex);