On Tue, May 8, 2018 at 12:36 AM, Darrick J. Wong
<darrick.wong@xxxxxxxxxx> wrote:
> On Sun, May 06, 2018 at 10:24:53AM -0700, Allison Henderson wrote:
>> This patch adds a new file ioctl to retrieve the parent
>> pointer of a given inode
>>
>> Signed-off-by: Allison Henderson <allison.henderson@xxxxxxxxxx>
>> ---
[...]
>> +
>> + /*
>> + * Now that we know how big the trailing buffer is, expand
>> + * our kernel xfs_pptr_info to be the same size
>> + */
>> + ppi = kmem_realloc(ppi, XFS_PPTR_INFO_SIZEOF(ppi->pi_ptrs_size),
>
> Hmm, pi_ptrs_size probably needs some kind of check so that userspace
> can't ask for insane large allocations. 64k, perhaps? ~230 records per
> call ought to be enough for anyone... :P
>
> if (XFS_PPTR_INFO_SIZEOFI(...) > XFS_XATTR_LIST_MAX)
> return -ENOMEM;
ERANGE feels more appropriate.
> ppi = kmem_realloc(...);
>
>> + KM_SLEEP);
>> + if (!ppi)
>> + return -ENOMEM;
>> +
>> + if (ppi->pi_flags == XFS_PPTR_IFLAG_HANDLE) {
>> + dentry = xfs_handle_to_dentry(filp, &ppi->pi_handle,
>> + sizeof(struct xfs_handle));
>> + if (IS_ERR(dentry))
>> + return PTR_ERR(dentry);
>> + ip = XFS_I(d_inode(dentry));
>
> I would've thought that between the dentry and the ip that at least one
> of those would require a dput/iput, and that we'd need to do something
> to prevent the dentry or the inode from disappearing from underneath us...
>
> ...but you could also extract the inode and generation numbers from the
> handle information and call xfs_iget directly. The exportfs code tries
> to reconnect dentry parent information up to the root, which will turn
> out badly if some mid-level directory is corrupt and scrub is trying to
> reconstruct the former path of a now inaccessible file.
>
Here is an easy code reuse solution for you.
It's a way to suppress reconnect and reuse of the conversions
done in xfs_handle_to_dentry().
Thanks,
Amir.
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 89fb1eb80aae..2312862dc34a 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -159,7 +159,8 @@ struct dentry *
xfs_handle_to_dentry(
struct file *parfilp,
void __user *uhandle,
- u32 hlen)
+ u32 hlen,
+ bool reconnect)
{
xfs_handle_t handle;
struct xfs_fid64 fid;
@@ -184,7 +185,7 @@ xfs_handle_to_dentry(
return exportfs_decode_fh(parfilp->f_path.mnt, (struct fid *)&fid, 3,
FILEID_INO32_GEN | XFS_FILEID_TYPE_64FLAG,
- xfs_handle_acceptable, NULL);
+ reconnect ? xfs_handle_acceptable : NULL, NULL);
}
STATIC struct dentry *
@@ -192,7 +193,8 @@ xfs_handlereq_to_dentry(
struct file *parfilp,
xfs_fsop_handlereq_t *hreq)
{
- return xfs_handle_to_dentry(parfilp, hreq->ihandle, hreq->ihandlen);
+ return xfs_handle_to_dentry(parfilp, hreq->ihandle, hreq->ihandlen,
+ false);
}
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