linux-kernel - [PATCH] afs: Fix updating of i

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Date:   Thu, 11 Feb 2021 10:37:14 +0000
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     marc.dionne@...istor.com, linux-afs@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] afs: Fix updating of i_mode due to 3rd party change

Fix afs_apply_status() to mask off the irrelevant bits from status->mode
when OR'ing them into i_mode.  This can happen when a 3rd party chmod
occurs.

Also fix afs_inode_init_from_status() to mask off the mode bits when
initialising i_mode.

Fixes: 260a980317da ("[AFS]: Add "directory write" support.")
Reported-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/inode.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index b0d7b892090d..d68abb9804b6 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -74,6 +74,7 @@ static int afs_inode_init_from_status(struct afs_operation *op,
 	struct afs_file_status *status = &vp->scb.status;
 	struct inode *inode = AFS_VNODE_TO_I(vnode);
 	struct timespec64 t;
+	mode_t mode = status->mode & S_IALLUGO;
 
 	_enter("{%llx:%llu.%u} %s",
 	       vp->fid.vid, vp->fid.vnode, vp->fid.unique,
@@ -103,13 +104,13 @@ static int afs_inode_init_from_status(struct afs_operation *op,
 
 	switch (status->type) {
 	case AFS_FTYPE_FILE:
-		inode->i_mode	= S_IFREG | status->mode;
+		inode->i_mode	= S_IFREG | mode;
 		inode->i_op	= &afs_file_inode_operations;
 		inode->i_fop	= &afs_file_operations;
 		inode->i_mapping->a_ops	= &afs_fs_aops;
 		break;
 	case AFS_FTYPE_DIR:
-		inode->i_mode	= S_IFDIR | status->mode;
+		inode->i_mode	= S_IFDIR | mode;
 		inode->i_op	= &afs_dir_inode_operations;
 		inode->i_fop	= &afs_dir_file_operations;
 		inode->i_mapping->a_ops	= &afs_dir_aops;
@@ -126,7 +127,7 @@ static int afs_inode_init_from_status(struct afs_operation *op,
 			inode->i_fop	= &afs_mntpt_file_operations;
 			inode->i_mapping->a_ops	= &afs_fs_aops;
 		} else {
-			inode->i_mode	= S_IFLNK | status->mode;
+			inode->i_mode	= S_IFLNK | mode;
 			inode->i_op	= &afs_symlink_inode_operations;
 			inode->i_mapping->a_ops	= &afs_fs_aops;
 		}
@@ -199,7 +200,7 @@ static void afs_apply_status(struct afs_operation *op,
 	if (status->mode != vnode->status.mode) {
 		mode = inode->i_mode;
 		mode &= ~S_IALLUGO;
-		mode |= status->mode;
+		mode |= status->mode & S_IALLUGO;
 		WRITE_ONCE(inode->i_mode, mode);
 	}