xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fs, nfs: convert nfs4_pnfs_ds.ds_count from atomic_t to refcount_t

Browse Source 
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 nfs4_pnfs_ds.ds_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 12:53:31 +03:00
committed by Anna Schumaker
parent 3be0f80b5f
commit a2a5dea7b6
2 changed files with 7 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
fs/nfs/pnfs_nfs.c
View File

@@ -338,7 +338,7 @@ print_ds(struct nfs4_pnfs_ds *ds)
" client %p\n"
" cl_exchange_flags %x\n",
ds->ds_remotestr,
atomic_read(&ds->ds_count), ds->ds_clp,
refcount_read(&ds->ds_count), ds->ds_clp,
ds->ds_clp ? ds->ds_clp->cl_exchange_flags : 0);
}
@@ -451,7 +451,7 @@ static void destroy_ds(struct nfs4_pnfs_ds *ds)
void nfs4_pnfs_ds_put(struct nfs4_pnfs_ds *ds)
{
if (atomic_dec_and_lock(&ds->ds_count,
if (refcount_dec_and_lock(&ds->ds_count,
&nfs4_ds_cache_lock)) {
list_del_init(&ds->ds_node);
spin_unlock(&nfs4_ds_cache_lock);
@@ -537,7 +537,7 @@ nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
INIT_LIST_HEAD(&ds->ds_addrs);
list_splice_init(dsaddrs, &ds->ds_addrs);
ds->ds_remotestr = remotestr;
atomic_set(&ds->ds_count, 1);
refcount_set(&ds->ds_count, 1);
INIT_LIST_HEAD(&ds->ds_node);
ds->ds_clp = NULL;
list_add(&ds->ds_node, &nfs4_data_server_cache);
@@ -546,10 +546,10 @@ nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
} else {
kfree(remotestr);
kfree(ds);
atomic_inc(&tmp_ds->ds_count);
refcount_inc(&tmp_ds->ds_count);
dprintk("%s data server %s found, inc'ed ds_count to %d\n",
__func__, tmp_ds->ds_remotestr,
atomic_read(&tmp_ds->ds_count));
refcount_read(&tmp_ds->ds_count));
ds = tmp_ds;
}
spin_unlock(&nfs4_ds_cache_lock);