On 6/5/18 4:23 PM, Arnd Bergmann wrote: > On Tue, Jun 5, 2018 at 8:44 PM, Eric Sandeen <sandeen@xxxxxxxxxxx> wrote: >> On 5/25/18 10:14 AM, Arnd Bergmann wrote: > >>> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c >>> index 84fbf164cbc3..eb79f2bc4dcc 100644 >>> --- a/fs/xfs/xfs_ioctl.c >>> +++ b/fs/xfs/xfs_ioctl.c >>> @@ -1819,12 +1819,12 @@ xfs_ioc_getlabel( >>> BUILD_BUG_ON(sizeof(sbp->sb_fname) > FSLABEL_MAX); >>> >>> spin_lock(&mp->m_sb_lock); >>> - strncpy(label, sbp->sb_fname, sizeof(sbp->sb_fname)); >>> + strncpy(label, sbp->sb_fname, XFSLABEL_MAX); >>> spin_unlock(&mp->m_sb_lock); >>> >>> /* xfs on-disk label is 12 chars, be sure we send a null to user */ >>> label[XFSLABEL_MAX] = '\0'; >>> - if (copy_to_user(user_label, label, sizeof(sbp->sb_fname))) >>> + if (copy_to_user(user_label, label, sizeof(label))) >> >> I /think/ this also runs the risk of copying out stack memory. >> >> I'll send another proposal based on this with slight modifications. > > I assumed it's safe since the earlier strncpy() pads the local 'label' > with zero bytes up the XFSLABEL_MAX, and the last byte > is explicitly set to guarantee zero padding. Ah you are right, I forgot that strncpy pads. Did I mention that I hate C strings... o_O In that case I suppose your original patch is fine, if you'd like to fix the "mark as nonstring" subject. Thanks, -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
