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[V2] xfs: remote attribute overwrite causes transaction overrun

To: xfs@xxxxxxxxxxx
Subject: [V2] xfs: remote attribute overwrite causes transaction overrun
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 5 May 2014 17:45:48 +1000
Delivered-to: xfs@xxxxxxxxxxx
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>
---
 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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