On Fri, Nov 6, 2015 at 6:36 PM, Justin Maggard <jmaggar...@gmail.com> wrote: > There's a race condition that leads to a NULL pointer dereference if you > disable quotas while a quota rescan is running. To fix this, we just need > to wait for the quota rescan worker to actually exit before tearing down > the quota structures. > > Signed-off-by: Justin Maggard <jmagg...@netgear.com>
Justin, it looks good and it's a very good find. But can you please give a more detailed change log? You mention a NULL pointer dereference, but you don't say where, which variable nor why. Pasting a trace of the crash you get in syslog/dmesg would also be nice. My guess is the null pointer dereference is in fs_info->quota_root, but running the corresponding xfstest once I hit the BUG_ON(!fs_info->quota_root) at btrfs_qgroup_account_extent(), called by the rescan worker through qgroup_rescan_leaf(). Once you add that, you can add as well: Reviewed-by: Filipe Manana <fdman...@suse.com> Thanks for this and the test. > --- > fs/btrfs/qgroup.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c > index 75c0249..a7cf504 100644 > --- a/fs/btrfs/qgroup.c > +++ b/fs/btrfs/qgroup.c > @@ -993,9 +993,10 @@ int btrfs_quota_disable(struct btrfs_trans_handle *trans, > mutex_lock(&fs_info->qgroup_ioctl_lock); > if (!fs_info->quota_root) > goto out; > - spin_lock(&fs_info->qgroup_lock); > fs_info->quota_enabled = 0; > fs_info->pending_quota_state = 0; > + btrfs_qgroup_wait_for_completion(fs_info); > + spin_lock(&fs_info->qgroup_lock); > quota_root = fs_info->quota_root; > fs_info->quota_root = NULL; > fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_ON; > -- > 2.6.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Filipe David Manana, "Reasonable men adapt themselves to the world. Unreasonable men adapt the world to themselves. That's why all progress depends on unreasonable men." -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
