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 pnfs_layout_hdr.plh_refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
---
fs/nfs/pnfs.c | 12 ++++++------
fs/nfs/pnfs.h | 2 +-
2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 499bb71..4aab53b 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -251,7 +251,7 @@ EXPORT_SYMBOL_GPL(pnfs_unregister_layoutdriver);
void
pnfs_get_layout_hdr(struct pnfs_layout_hdr *lo)
{
- atomic_inc(&lo->plh_refcount);
+ refcount_inc(&lo->plh_refcount);
}
static struct pnfs_layout_hdr *
@@ -296,7 +296,7 @@ pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
pnfs_layoutreturn_before_put_layout_hdr(lo);
- if (atomic_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
+ if (refcount_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
if (!list_empty(&lo->plh_segs))
WARN_ONCE(1, "NFS: BUG unfreed layout segments.\n");
pnfs_detach_layout_hdr(lo);
@@ -395,14 +395,14 @@ pnfs_layout_set_fail_bit(struct pnfs_layout_hdr *lo, int fail_bit)
{
lo->plh_retry_timestamp = jiffies;
if (!test_and_set_bit(fail_bit, &lo->plh_flags))
- atomic_inc(&lo->plh_refcount);
+ refcount_inc(&lo->plh_refcount);
}
static void
pnfs_layout_clear_fail_bit(struct pnfs_layout_hdr *lo, int fail_bit)
{
if (test_and_clear_bit(fail_bit, &lo->plh_flags))
- atomic_dec(&lo->plh_refcount);
+ refcount_dec(&lo->plh_refcount);
}
static void
@@ -472,7 +472,7 @@ pnfs_layout_remove_lseg(struct pnfs_layout_hdr *lo,
WARN_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
list_del_init(&lseg->pls_list);
/* Matched by pnfs_get_layout_hdr in pnfs_layout_insert_lseg */
- atomic_dec(&lo->plh_refcount);
+ refcount_dec(&lo->plh_refcount);
if (test_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags))
return;
if (list_empty(&lo->plh_segs) &&
@@ -1451,7 +1451,7 @@ alloc_init_layout_hdr(struct inode *ino,
lo = pnfs_alloc_layout_hdr(ino, gfp_flags);
if (!lo)
return NULL;
- atomic_set(&lo->plh_refcount, 1);
+ refcount_set(&lo->plh_refcount, 1);
INIT_LIST_HEAD(&lo->plh_layouts);
INIT_LIST_HEAD(&lo->plh_segs);
INIT_LIST_HEAD(&lo->plh_return_segs);
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index f0e98e1..78de7a2 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -180,7 +180,7 @@ struct pnfs_layoutdriver_type {
};
struct pnfs_layout_hdr {
- atomic_t plh_refcount;
+ refcount_t plh_refcount;
atomic_t plh_outstanding; /* number of RPCs out */
struct list_head plh_layouts; /* other client layouts */
struct list_head plh_bulk_destroy;
--
2.7.4
--
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