On Mon, Apr 21, 2014 at 08:46:39PM +0800, Jeff Liu wrote:
> Hi Tuomas,
>
> On 04/21 2014 18:04 PM, Tuomas Tynkkynen wrote:
> > xfs_{compat_,}attrmulti_by_handle could return an errno with incorrect
> > sign in some cases. While at it, make sure ENOMEM is returned instead of
> > E2BIG if kmalloc fails.
> >
> > Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@xxxxxx>
> > ---
> > Compile tested only. For the ERANGE case, I also wonder if it should
> > be assigning to ops[i].am_error instead of error, and/or have a break.
>
> If I understand right, ops[i].am_error is used to save the internal operation result,
> i.e, xfs_attrmult_attr_get{set}... but error is used for the ioctl call results.
> Therefore, assign ERANGE to error is compatible with the VFS set{get}xattr syscalls in
> case of "if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)".
>
But we set 'error' in this case and effectively try to continue the operation
whereas the traditional vfs path returns...
> It seems that we don't need to have a break in this case because xfs_attrmulti_by_handle()
> is used to process multiple attrs. Hence if a given attrname in ops array is invalid,
> the am_error will indicate that with ENOATTR or EFAULT...but it should proceed to loop
> through the left array members.
>
Perhaps so if am_error == 0, but it depends on what attr_name contains
at that point (stale data?). Otherwise, we try to proceed with a
truncated name. It looks like the consistent thing to do would be set
am_error to ERANGE and continue (i.e., skip the op and move on to the
next).
Brian
> Also, looks there is another minor issue at xfs_attrmulti_attr_set(), we should return
> -PTR_ERR(kbuf) if call memdup_user() failed.
>
> >
> > fs/xfs/xfs_ioctl.c | 5 +++--
> > fs/xfs/xfs_ioctl32.c | 5 +++--
> > 2 files changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index 0b18776..2d8f4fd 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -543,10 +543,11 @@ xfs_attrmulti_by_handle(
> >
> > ops = memdup_user(am_hreq.ops, size);
> > if (IS_ERR(ops)) {
> > - error = PTR_ERR(ops);
> > + error = -PTR_ERR(ops);
> > goto out_dput;
> > }
> >
> > + error = ENOMEM;
> > attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
> > if (!attr_name)
> > goto out_kfree_ops;
> > @@ -556,7 +557,7 @@ xfs_attrmulti_by_handle(
> > ops[i].am_error = strncpy_from_user((char *)attr_name,
> > ops[i].am_attrname, MAXNAMELEN);
> > if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
> > - error = -ERANGE;
> > + error = ERANGE;
> > if (ops[i].am_error < 0)
> > break;
> >
> > diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> > index a7992f8..944d5ba 100644
> > --- a/fs/xfs/xfs_ioctl32.c
> > +++ b/fs/xfs/xfs_ioctl32.c
> > @@ -424,10 +424,11 @@ xfs_compat_attrmulti_by_handle(
> >
> > ops = memdup_user(compat_ptr(am_hreq.ops), size);
> > if (IS_ERR(ops)) {
> > - error = PTR_ERR(ops);
> > + error = -PTR_ERR(ops);
> > goto out_dput;
> > }
> >
> > + error = ENOMEM;
> > attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
> > if (!attr_name)
> > goto out_kfree_ops;
> > @@ -438,7 +439,7 @@ xfs_compat_attrmulti_by_handle(
> > compat_ptr(ops[i].am_attrname),
> > MAXNAMELEN);
> > if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
> > - error = -ERANGE;
> > + error = ERANGE;
> > if (ops[i].am_error < 0)
> > break;
> >
>
> Thanks,
> -Jeff
>
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