| Message ID | 20170516192748.GQ4519@birch.djwong.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Tue, May 16, 2017 at 12:27:48PM -0700, Darrick J. Wong wrote: > If a malicious user corrupts the refcount btree to cause a cycle between > different levels of the tree, the next mount attempt will deadlock in > the CoW recovery routine while grabbing buffer locks. We can use the > ability to re-grab a buffer that was previous locked to a transaction to > avoid deadlocks, so do that here. > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Missing comments in the code explaining the deadlock being avoided by using xfs_trans_alloc_empty().... Cheers, Dave.
On Wed, May 17, 2017 at 10:39:31AM +1000, Dave Chinner wrote: > On Tue, May 16, 2017 at 12:27:48PM -0700, Darrick J. Wong wrote: > > If a malicious user corrupts the refcount btree to cause a cycle between > > different levels of the tree, the next mount attempt will deadlock in > > the CoW recovery routine while grabbing buffer locks. We can use the > > ability to re-grab a buffer that was previous locked to a transaction to > > avoid deadlocks, so do that here. > > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > > Missing comments in the code explaining the deadlock being avoided > by using xfs_trans_alloc_empty().... Heh, ok. --D > > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c index b177ef3..6fd337c 100644 --- a/fs/xfs/libxfs/xfs_refcount.c +++ b/fs/xfs/libxfs/xfs_refcount.c @@ -1629,10 +1629,14 @@ xfs_refcount_recover_cow_leftovers( if (mp->m_sb.sb_agblocks >= XFS_REFC_COW_START) return -EOPNOTSUPP; - error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp); + error = xfs_trans_alloc_empty(mp, &tp); if (error) return error; - cur = xfs_refcountbt_init_cursor(mp, NULL, agbp, agno, NULL); + + error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp); + if (error) + goto out_trans; + cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno, NULL); /* Find all the leftover CoW staging extents. */ INIT_LIST_HEAD(&debris); @@ -1645,10 +1649,11 @@ xfs_refcount_recover_cow_leftovers( if (error) goto out_cursor; xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR); - xfs_buf_relse(agbp); + xfs_trans_brelse(tp, agbp); + xfs_trans_cancel(tp); /* Now iterate the list to free the leftovers */ - list_for_each_entry(rr, &debris, rr_list) { + list_for_each_entry_safe(rr, n, &debris, rr_list) { /* Set up transaction. */ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp); if (error) @@ -1676,8 +1681,15 @@ xfs_refcount_recover_cow_leftovers( error = xfs_trans_commit(tp); if (error) goto out_free; + + list_del(&rr->rr_list); + kmem_free(rr); } + return error; +out_defer: + xfs_defer_cancel(&dfops); + xfs_trans_cancel(tp); out_free: /* Free the leftover list */ list_for_each_entry_safe(rr, n, &debris, rr_list) { @@ -1688,11 +1700,8 @@ xfs_refcount_recover_cow_leftovers( out_cursor: xfs_btree_del_cursor(cur, XFS_BTREE_ERROR); - xfs_buf_relse(agbp); - goto out_free; - -out_defer: - xfs_defer_cancel(&dfops); + xfs_trans_brelse(tp, agbp); +out_trans: xfs_trans_cancel(tp); - goto out_free; + return error; }
If a malicious user corrupts the refcount btree to cause a cycle between different levels of the tree, the next mount attempt will deadlock in the CoW recovery routine while grabbing buffer locks. We can use the ability to re-grab a buffer that was previous locked to a transaction to avoid deadlocks, so do that here. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> --- fs/xfs/libxfs/xfs_refcount.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html