linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Miklos Szeredi <mszeredi@redhat.com>
Subject: [PATCH 4.4 06/25] fuse: fix killing s[ug]id in setattr
Date: Fri, 21 Oct 2016 11:15:57 +0200	[thread overview]
Message-ID: <20161021091413.542506761@linuxfoundation.org> (raw)
In-Reply-To: <20161021091413.053290730@linuxfoundation.org>

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@redhat.com>

commit a09f99eddef44035ec764075a37bace8181bec38 upstream.

Fuse allowed VFS to set mode in setattr in order to clear suid/sgid on
chown and truncate, and (since writeback_cache) write.  The problem with
this is that it'll potentially restore a stale mode.

The poper fix would be to let the filesystems do the suid/sgid clearing on
the relevant operations.  Possibly some are already doing it but there's no
way we can detect this.

So fix this by refreshing and recalculating the mode.  Do this only if
ATTR_KILL_S[UG]ID is set to not destroy performance for writes.  This is
still racy but the size of the window is reduced.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/fuse/dir.c |   32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1697,16 +1697,40 @@ error:
 static int fuse_setattr(struct dentry *entry, struct iattr *attr)
 {
 	struct inode *inode = d_inode(entry);
+	struct file *file = (attr->ia_valid & ATTR_FILE) ? attr->ia_file : NULL;
 	int ret;
 
 	if (!fuse_allow_current_process(get_fuse_conn(inode)))
 		return -EACCES;
 
-	if (attr->ia_valid & ATTR_FILE)
-		ret = fuse_do_setattr(inode, attr, attr->ia_file);
-	else
-		ret = fuse_do_setattr(inode, attr, NULL);
+	if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) {
+		int kill;
 
+		attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID |
+				    ATTR_MODE);
+		/*
+		 * ia_mode calculation may have used stale i_mode.  Refresh and
+		 * recalculate.
+		 */
+		ret = fuse_do_getattr(inode, NULL, file);
+		if (ret)
+			return ret;
+
+		attr->ia_mode = inode->i_mode;
+		kill = should_remove_suid(entry);
+		if (kill & ATTR_KILL_SUID) {
+			attr->ia_valid |= ATTR_MODE;
+			attr->ia_mode &= ~S_ISUID;
+		}
+		if (kill & ATTR_KILL_SGID) {
+			attr->ia_valid |= ATTR_MODE;
+			attr->ia_mode &= ~S_ISGID;
+		}
+	}
+	if (!attr->ia_valid)
+		return 0;
+
+	ret = fuse_do_setattr(inode, attr, file);
 	if (!ret) {
 		/* Directory mode changed, may need to revalidate access */
 		if (d_is_dir(entry) && (attr->ia_valid & ATTR_MODE))

  parent reply	other threads:[~2016-10-21  9:17 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20161021091628uscas1p21e03f35d4481162f8066d9056c8aeb3c@uscas1p2.samsung.com>
2016-10-21  9:15 ` [PATCH 4.4 00/25] 4.4.27-stable review Greg Kroah-Hartman
2016-10-21  9:15   ` [PATCH 4.4 01/25] serial: 8250_dw: Check the data->pclk when get apb_pclk Greg Kroah-Hartman
2016-10-21  9:15   ` [PATCH 4.4 02/25] btrfs: assign error values to the correct bio structs Greg Kroah-Hartman
2016-10-21  9:15   ` [PATCH 4.4 03/25] drivers: base: dma-mapping: page align the size when unmap_kernel_range Greg Kroah-Hartman
2016-10-21  9:15   ` [PATCH 4.4 04/25] fuse: listxattr: verify xattr list Greg Kroah-Hartman
2016-10-21  9:15   ` Greg Kroah-Hartman [this message]
2016-10-21  9:15   ` [PATCH 4.4 07/25] i40e: avoid NULL pointer dereference and recursive errors on early PCI error Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 09/25] ASoC: Intel: Atom: add a missing star in a memcpy call Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 10/25] reiserfs: Unlock superblock before calling reiserfs_quota_on_mount() Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 11/25] reiserfs: switch to generic_{get,set,remove}xattr() Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 12/25] async_pq_val: fix DMA memory leak Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 13/25] scsi: arcmsr: Buffer overflow in arcmsr_iop_message_xfer() Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 14/25] scsi: arcmsr: Simplify user_len checking Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 15/25] scsi: ibmvfc: Fix I/O hang when port is not mapped Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 16/25] ext4: enforce online defrag restriction for encrypted files Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 17/25] ext4: reinforce check of i_dtime when clearing high fields of uid and gid Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 18/25] ext4: fix memory leak in ext4_insert_range() Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 19/25] ext4: allow DAX writeback for hole punch Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 20/25] ext4: release bh in make_indexed_dir Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 21/25] crypto: ghash-generic - move common definitions to a new header file Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 22/25] crypto: vmx - Fix memory corruption caused by p8_ghash Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 23/25] dlm: free workqueues after the connections Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 24/25] vfs: move permission checking into notify_change() for utimes(NULL) Greg Kroah-Hartman
2016-10-21  9:16   ` [PATCH 4.4 25/25] cfq: fix starvation of asynchronous writes Greg Kroah-Hartman
2016-10-21 15:44   ` [PATCH 4.4 00/25] 4.4.27-stable review Shuah Khan
2016-10-21 19:16   ` Guenter Roeck

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20161021091413.542506761@linuxfoundation.org \
    --to=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mszeredi@redhat.com \
    --cc=stable@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).