diff mbox series

[25/31] xfs: actually check the fsid of a handle

Message ID 171323028194.251715.15160167066761168436.stgit@frogsfrogsfrogs (mailing list archive)
State New
Headers show
Series [01/31] xfs: rearrange xfs_attr_match parameters | expand

Commit Message

Darrick J. Wong April 16, 2024, 1:32 a.m. UTC 
From: Darrick J. Wong <djwong@kernel.org>

Compare the fsid of a handle to m_fixedfsid so that we don't try to open
a handle from the wrong fs and get lucky if the ino/gen happen to match.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/xfs_handle.c |    4 ++++
 1 file changed, 4 insertions(+)

Comments

Christoph Hellwig April 16, 2024, 5:19 a.m. UTC | #1 
On Mon, Apr 15, 2024 at 06:32:33PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Compare the fsid of a handle to m_fixedfsid so that we don't try to open
> a handle from the wrong fs and get lucky if the ino/gen happen to match.

I don't think this is a good idea.  It'll break so far perfectly valid uses
of the handle API when userspace hancrafted the handles or stored them
in a more compact format.
Darrick J. Wong April 16, 2024, 5:44 p.m. UTC | #2 
On Mon, Apr 15, 2024 at 10:19:36PM -0700, Christoph Hellwig wrote:
> On Mon, Apr 15, 2024 at 06:32:33PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > Compare the fsid of a handle to m_fixedfsid so that we don't try to open
> > a handle from the wrong fs and get lucky if the ino/gen happen to match.
> 
> I don't think this is a good idea.  It'll break so far perfectly valid uses
> of the handle API when userspace hancrafted the handles or stored them
> in a more compact format.

Ah, ok.  It'll break userspace, and for the bad-fsid case you'll
probably get an error code unless you get lucky and guess the generation
correctly.  Will drop this patch.

--D
diff mbox series

Patch

diff --git a/fs/xfs/xfs_handle.c b/fs/xfs/xfs_handle.c
index b9f4d9860682a..417e4a1f5e6cb 100644
--- a/fs/xfs/xfs_handle.c
+++ b/fs/xfs/xfs_handle.c
@@ -163,6 +163,7 @@  xfs_khandle_to_dentry(
 		.ino		= handle->ha_fid.fid_ino,
 		.gen		= handle->ha_fid.fid_gen,
 	};
+	struct xfs_mount	*mp = XFS_I(file_inode(file))->i_mount;
 
 	/*
 	 * Only allow handle opens under a directory.
@@ -170,6 +171,9 @@  xfs_khandle_to_dentry(
 	if (!S_ISDIR(file_inode(file)->i_mode))
 		return ERR_PTR(-ENOTDIR);
 
+	if (memcmp(&handle->ha_fsid, mp->m_fixedfsid, sizeof(struct xfs_fsid)))
+		return ERR_PTR(-ESTALE);
+
 	if (handle->ha_fid.fid_len != xfs_filehandle_fid_len())
 		return ERR_PTR(-EINVAL);