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Re: [V2] xfs: remote attribute overwrite causes transaction overrun

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [V2] xfs: remote attribute overwrite causes transaction overrun
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Mon, 5 May 2014 15:30:09 -0400
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1399275948-27752-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1399275948-27752-1-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, May 05, 2014 at 05:45:48PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> Commit e461fcb ("xfs: remote attribute lookups require the value
> length") passes the remote attribute length in the xfs_da_args
> structure on lookup so that CRC calculations and validity checking
> can be performed correctly by related code. This, unfortunately has
> the side effect of changing the args->valuelen parameter in cases
> where it shouldn't.
> 
> That is, when we replace a remote attribute, the incoming
> replacement stores the value and length in args->value and
> args->valuelen, but then the lookup which finds the existing remote
> attribute overwrites args->valuelen with the length of the remote
> attribute being replaced. Hence when we go to create the new
> attribute, we create it of the size of the existing remote
> attribute, not the size it is supposed to be. When the new attribute
> is much smaller than the old attribute, this results in a
> transaction overrun and an ASSERT() failure on a debug kernel:
> 
> XFS: Assertion failed: tp->t_blk_res_used <= tp->t_blk_res, file: 
> fs/xfs/xfs_trans.c, line: 331
> 
> Fix this by keeping the remote attribute value length separate to
> the attribute value length in the xfs_da_args structure. The enables
> us to pass the length of the remote attribute to be removed without
> overwriting the new attribute's length.
> 
> Also, ensure that when we save remote block contexts for a later
> rename we zero the original state variables so that we don't confuse
> the state of the attribute to be removes with the state of the new
> attribute that we just added. [Spotted by Brain Foster.]
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---

Looks good to me..

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

>  fs/xfs/xfs_attr.c        | 24 +++++++++++++++++++++++-
>  fs/xfs/xfs_attr_leaf.c   | 21 +++++++++++----------
>  fs/xfs/xfs_attr_list.c   |  1 +
>  fs/xfs/xfs_attr_remote.c |  8 +++++---
>  fs/xfs/xfs_da_btree.h    |  2 ++
>  5 files changed, 42 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/xfs/xfs_attr.c b/fs/xfs/xfs_attr.c
> index 95de302..30482c9 100644
> --- a/fs/xfs/xfs_attr.c
> +++ b/fs/xfs/xfs_attr.c
> @@ -213,7 +213,7 @@ xfs_attr_calc_size(
>                * Out of line attribute, cannot double split, but
>                * make room for the attribute value itself.
>                */
> -             uint    dblocks = XFS_B_TO_FSB(mp, valuelen);
> +             uint    dblocks = xfs_attr3_rmt_blocks(mp, valuelen);
>               nblks += dblocks;
>               nblks += XFS_NEXTENTADD_SPACE_RES(mp, dblocks, XFS_ATTR_FORK);
>       }
> @@ -698,11 +698,22 @@ xfs_attr_leaf_addname(xfs_da_args_t *args)
>  
>               trace_xfs_attr_leaf_replace(args);
>  
> +             /* save the attribute state for later removal*/
>               args->op_flags |= XFS_DA_OP_RENAME;     /* an atomic rename */
>               args->blkno2 = args->blkno;             /* set 2nd entry info*/
>               args->index2 = args->index;
>               args->rmtblkno2 = args->rmtblkno;
>               args->rmtblkcnt2 = args->rmtblkcnt;
> +             args->rmtvaluelen2 = args->rmtvaluelen;
> +
> +             /*
> +              * clear the remote attr state now that it is saved so that the
> +              * values reflect the state of the attribute we are about to
> +              * add, not the attribute we just found and will remove later.
> +              */
> +             args->rmtblkno = 0;
> +             args->rmtblkcnt = 0;
> +             args->rmtvaluelen = 0;
>       }
>  
>       /*
> @@ -794,6 +805,7 @@ xfs_attr_leaf_addname(xfs_da_args_t *args)
>               args->blkno = args->blkno2;
>               args->rmtblkno = args->rmtblkno2;
>               args->rmtblkcnt = args->rmtblkcnt2;
> +             args->rmtvaluelen = args->rmtvaluelen2;
>               if (args->rmtblkno) {
>                       error = xfs_attr_rmtval_remove(args);
>                       if (error)
> @@ -999,13 +1011,22 @@ restart:
>  
>               trace_xfs_attr_node_replace(args);
>  
> +             /* save the attribute state for later removal*/
>               args->op_flags |= XFS_DA_OP_RENAME;     /* atomic rename op */
>               args->blkno2 = args->blkno;             /* set 2nd entry info*/
>               args->index2 = args->index;
>               args->rmtblkno2 = args->rmtblkno;
>               args->rmtblkcnt2 = args->rmtblkcnt;
> +             args->rmtvaluelen2 = args->rmtvaluelen;
> +
> +             /*
> +              * clear the remote attr state now that it is saved so that the
> +              * values reflect the state of the attribute we are about to
> +              * add, not the attribute we just found and will remove later.
> +              */
>               args->rmtblkno = 0;
>               args->rmtblkcnt = 0;
> +             args->rmtvaluelen = 0;
>       }
>  
>       retval = xfs_attr3_leaf_add(blk->bp, state->args);
> @@ -1133,6 +1154,7 @@ restart:
>               args->blkno = args->blkno2;
>               args->rmtblkno = args->rmtblkno2;
>               args->rmtblkcnt = args->rmtblkcnt2;
> +             args->rmtvaluelen = args->rmtvaluelen2;
>               if (args->rmtblkno) {
>                       error = xfs_attr_rmtval_remove(args);
>                       if (error)
> diff --git a/fs/xfs/xfs_attr_leaf.c b/fs/xfs/xfs_attr_leaf.c
> index b9d9170..17ec23f 100644
> --- a/fs/xfs/xfs_attr_leaf.c
> +++ b/fs/xfs/xfs_attr_leaf.c
> @@ -1229,6 +1229,7 @@ xfs_attr3_leaf_add_work(
>               name_rmt->valueblk = 0;
>               args->rmtblkno = 1;
>               args->rmtblkcnt = xfs_attr3_rmt_blocks(mp, args->valuelen);
> +             args->rmtvaluelen = args->valuelen;
>       }
>       xfs_trans_log_buf(args->trans, bp,
>            XFS_DA_LOGRANGE(leaf, xfs_attr3_leaf_name(leaf, args->index),
> @@ -2167,11 +2168,11 @@ xfs_attr3_leaf_lookup_int(
>                       if (!xfs_attr_namesp_match(args->flags, entry->flags))
>                               continue;
>                       args->index = probe;
> -                     args->valuelen = be32_to_cpu(name_rmt->valuelen);
> +                     args->rmtvaluelen = be32_to_cpu(name_rmt->valuelen);
>                       args->rmtblkno = be32_to_cpu(name_rmt->valueblk);
>                       args->rmtblkcnt = xfs_attr3_rmt_blocks(
>                                                       args->dp->i_mount,
> -                                                     args->valuelen);
> +                                                     args->rmtvaluelen);
>                       return XFS_ERROR(EEXIST);
>               }
>       }
> @@ -2220,19 +2221,19 @@ xfs_attr3_leaf_getvalue(
>               name_rmt = xfs_attr3_leaf_name_remote(leaf, args->index);
>               ASSERT(name_rmt->namelen == args->namelen);
>               ASSERT(memcmp(args->name, name_rmt->name, args->namelen) == 0);
> -             valuelen = be32_to_cpu(name_rmt->valuelen);
> +             args->rmtvaluelen = be32_to_cpu(name_rmt->valuelen);
>               args->rmtblkno = be32_to_cpu(name_rmt->valueblk);
>               args->rmtblkcnt = xfs_attr3_rmt_blocks(args->dp->i_mount,
> -                                                    valuelen);
> +                                                    args->rmtvaluelen);
>               if (args->flags & ATTR_KERNOVAL) {
> -                     args->valuelen = valuelen;
> +                     args->valuelen = args->rmtvaluelen;
>                       return 0;
>               }
> -             if (args->valuelen < valuelen) {
> -                     args->valuelen = valuelen;
> +             if (args->valuelen < args->rmtvaluelen) {
> +                     args->valuelen = args->rmtvaluelen;
>                       return XFS_ERROR(ERANGE);
>               }
> -             args->valuelen = valuelen;
> +             args->valuelen = args->rmtvaluelen;
>       }
>       return 0;
>  }
> @@ -2519,7 +2520,7 @@ xfs_attr3_leaf_clearflag(
>               ASSERT((entry->flags & XFS_ATTR_LOCAL) == 0);
>               name_rmt = xfs_attr3_leaf_name_remote(leaf, args->index);
>               name_rmt->valueblk = cpu_to_be32(args->rmtblkno);
> -             name_rmt->valuelen = cpu_to_be32(args->valuelen);
> +             name_rmt->valuelen = cpu_to_be32(args->rmtvaluelen);
>               xfs_trans_log_buf(args->trans, bp,
>                        XFS_DA_LOGRANGE(leaf, name_rmt, sizeof(*name_rmt)));
>       }
> @@ -2677,7 +2678,7 @@ xfs_attr3_leaf_flipflags(
>               ASSERT((entry1->flags & XFS_ATTR_LOCAL) == 0);
>               name_rmt = xfs_attr3_leaf_name_remote(leaf1, args->index);
>               name_rmt->valueblk = cpu_to_be32(args->rmtblkno);
> -             name_rmt->valuelen = cpu_to_be32(args->valuelen);
> +             name_rmt->valuelen = cpu_to_be32(args->rmtvaluelen);
>               xfs_trans_log_buf(args->trans, bp1,
>                        XFS_DA_LOGRANGE(leaf1, name_rmt, sizeof(*name_rmt)));
>       }
> diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
> index 3e9a65a..0bba7c3 100644
> --- a/fs/xfs/xfs_attr_list.c
> +++ b/fs/xfs/xfs_attr_list.c
> @@ -447,6 +447,7 @@ xfs_attr3_leaf_list_int(
>                               args.dp = context->dp;
>                               args.whichfork = XFS_ATTR_FORK;
>                               args.valuelen = valuelen;
> +                             args.rmtvaluelen = valuelen;
>                               args.value = kmem_alloc(valuelen, KM_SLEEP | 
> KM_NOFS);
>                               args.rmtblkno = be32_to_cpu(name_rmt->valueblk);
>                               args.rmtblkcnt = xfs_attr3_rmt_blocks(
> diff --git a/fs/xfs/xfs_attr_remote.c b/fs/xfs/xfs_attr_remote.c
> index 44a57c8..6a70e7e 100644
> --- a/fs/xfs/xfs_attr_remote.c
> +++ b/fs/xfs/xfs_attr_remote.c
> @@ -337,7 +337,7 @@ xfs_attr_rmtval_get(
>       struct xfs_buf          *bp;
>       xfs_dablk_t             lblkno = args->rmtblkno;
>       __uint8_t               *dst = args->value;
> -     int                     valuelen = args->valuelen;
> +     int                     valuelen;
>       int                     nmap;
>       int                     error;
>       int                     blkcnt = args->rmtblkcnt;
> @@ -347,7 +347,9 @@ xfs_attr_rmtval_get(
>       trace_xfs_attr_rmtval_get(args);
>  
>       ASSERT(!(args->flags & ATTR_KERNOVAL));
> +     ASSERT(args->rmtvaluelen == args->valuelen);
>  
> +     valuelen = args->rmtvaluelen;
>       while (valuelen > 0) {
>               nmap = ATTR_RMTVALUE_MAPSIZE;
>               error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
> @@ -415,7 +417,7 @@ xfs_attr_rmtval_set(
>        * attributes have headers, we can't just do a straight byte to FSB
>        * conversion and have to take the header space into account.
>        */
> -     blkcnt = xfs_attr3_rmt_blocks(mp, args->valuelen);
> +     blkcnt = xfs_attr3_rmt_blocks(mp, args->rmtvaluelen);
>       error = xfs_bmap_first_unused(args->trans, args->dp, blkcnt, &lfileoff,
>                                                  XFS_ATTR_FORK);
>       if (error)
> @@ -480,7 +482,7 @@ xfs_attr_rmtval_set(
>        */
>       lblkno = args->rmtblkno;
>       blkcnt = args->rmtblkcnt;
> -     valuelen = args->valuelen;
> +     valuelen = args->rmtvaluelen;
>       while (valuelen > 0) {
>               struct xfs_buf  *bp;
>               xfs_daddr_t     dblkno;
> diff --git a/fs/xfs/xfs_da_btree.h b/fs/xfs/xfs_da_btree.h
> index 6e95ea7..201c609 100644
> --- a/fs/xfs/xfs_da_btree.h
> +++ b/fs/xfs/xfs_da_btree.h
> @@ -60,10 +60,12 @@ typedef struct xfs_da_args {
>       int             index;          /* index of attr of interest in blk */
>       xfs_dablk_t     rmtblkno;       /* remote attr value starting blkno */
>       int             rmtblkcnt;      /* remote attr value block count */
> +     int             rmtvaluelen;    /* remote attr value length in bytes */
>       xfs_dablk_t     blkno2;         /* blkno of 2nd attr leaf of interest */
>       int             index2;         /* index of 2nd attr in blk */
>       xfs_dablk_t     rmtblkno2;      /* remote attr value starting blkno */
>       int             rmtblkcnt2;     /* remote attr value block count */
> +     int             rmtvaluelen2;   /* remote attr value length in bytes */
>       int             op_flags;       /* operation flags */
>       enum xfs_dacmp  cmpresult;      /* name compare result for lookups */
>  } xfs_da_args_t;
> -- 
> 1.9.0
> 
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