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fs, nfs: convert nfs_client.cl_count from atomic_t to refcount_t

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atomic_t variables are currently used to implement reference
counters with the following properties:
 - counter is initialized to 1 using atomic_set()
 - a resource is freed upon counter reaching zero
 - once counter reaches zero, its further
   increments aren't allowed
 - counter schema uses basic atomic operations
   (set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable nfs_client.cl_count is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Elena Reshetova
2017-10-20 12:53:38 +03:00
committed by Anna Schumaker
parent 2f62b5aa48
commit 212bf41d88
7 changed files with 33 additions and 32 deletions
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12
fs/nfs/filelayout/filelayout.c
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@@ -471,10 +471,10 @@ filelayout_read_pagelist(struct nfs_pgio_header *hdr)
return PNFS_NOT_ATTEMPTED;
dprintk("%s USE DS: %s cl_count %d\n", __func__,
ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));
ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count));
/* No multipath support. Use first DS */
atomic_inc(&ds->ds_clp->cl_count);
refcount_inc(&ds->ds_clp->cl_count);
hdr->ds_clp = ds->ds_clp;
hdr->ds_commit_idx = idx;
fh = nfs4_fl_select_ds_fh(lseg, j);
@@ -515,10 +515,10 @@ filelayout_write_pagelist(struct nfs_pgio_header *hdr, int sync)
dprintk("%s ino %lu sync %d req %zu@%llu DS: %s cl_count %d\n",
__func__, hdr->inode->i_ino, sync, (size_t) hdr->args.count,
offset, ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));
offset, ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count));
hdr->pgio_done_cb = filelayout_write_done_cb;
atomic_inc(&ds->ds_clp->cl_count);
refcount_inc(&ds->ds_clp->cl_count);
hdr->ds_clp = ds->ds_clp;
hdr->ds_commit_idx = idx;
fh = nfs4_fl_select_ds_fh(lseg, j);
@@ -1064,9 +1064,9 @@ static int filelayout_initiate_commit(struct nfs_commit_data *data, int how)
goto out_err;
dprintk("%s ino %lu, how %d cl_count %d\n", __func__,
data->inode->i_ino, how, atomic_read(&ds->ds_clp->cl_count));
data->inode->i_ino, how, refcount_read(&ds->ds_clp->cl_count));
data->commit_done_cb = filelayout_commit_done_cb;
atomic_inc(&ds->ds_clp->cl_count);
refcount_inc(&ds->ds_clp->cl_count);
data->ds_clp = ds->ds_clp;
fh = select_ds_fh_from_commit(lseg, data->ds_commit_index);
if (fh)