From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit 51234eac5dd8b5feda9a3a8fa766f5398ecf91e3 ]
commit b99c2d913810e56682a538c9f2394d76fca808f8 upstream.
Before 4bacc9c9234c ("overlayfs: Make f_path...") file->f_path pointed to
the underlying file, hence suid/sgid removal on write worked fine.
After that patch file->f_path pointed to the overlay file, and the file
mode bits weren't copied to overlay_inode->i_mode. So the suid/sgid
removal simply stopped working.
The fix is to copy the mode bits, but then ovl_setattr() needs to clear
ATTR_MODE to avoid the BUG() in notify_change(). So do this first, then in
the next patch copy the mode.
Reported-by: Eryu Guan <eguan@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
fs/overlayfs/inode.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index edd2a4a..34c184b 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -67,6 +67,10 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
upperdentry = ovl_dentry_upper(dentry);
mutex_lock(&upperdentry->d_inode->i_mutex);
+
+ if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
+ attr->ia_valid &= ~ATTR_MODE;
+
err = notify_change(upperdentry, attr, NULL);
if (!err)
ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
--
2.7.4
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