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fs, nfs: convert nfs4_ff_layout_mirror.ref 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 nfs4_ff_layout_mirror.ref 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 12:53:34 +03:00 committed by Anna Schumaker
parent 2b28a7bee4
commit 81a090b997
2 changed files with 6 additions and 5 deletions
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8
fs/nfs/flexfilelayout/flexfilelayout.c
View file

@ -187,7 +187,7 @@ ff_layout_add_mirror(struct pnfs_layout_hdr *lo,
continue;
if (!ff_mirror_match_fh(mirror, pos))
continue;
if (atomic_inc_not_zero(&pos->ref)) {
if (refcount_inc_not_zero(&pos->ref)) {
spin_unlock(&inode->i_lock);
return pos;
}
@ -218,7 +218,7 @@ static struct nfs4_ff_layout_mirror *ff_layout_alloc_mirror(gfp_t gfp_flags)
mirror = kzalloc(sizeof(*mirror), gfp_flags);
if (mirror != NULL) {
spin_lock_init(&mirror->lock);
atomic_set(&mirror->ref, 1);
refcount_set(&mirror->ref, 1);
INIT_LIST_HEAD(&mirror->mirrors);
}
return mirror;
@ -242,7 +242,7 @@ static void ff_layout_free_mirror(struct nfs4_ff_layout_mirror *mirror)
static void ff_layout_put_mirror(struct nfs4_ff_layout_mirror *mirror)
{
if (mirror != NULL && atomic_dec_and_test(&mirror->ref))
if (mirror != NULL && refcount_dec_and_test(&mirror->ref))
ff_layout_free_mirror(mirror);
}
@ -2286,7 +2286,7 @@ ff_layout_mirror_prepare_stats(struct pnfs_layout_hdr *lo,
if (!test_and_clear_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags))
continue;
/* mirror refcount put in cleanup_layoutstats */
if (!atomic_inc_not_zero(&mirror->ref))
if (!refcount_inc_not_zero(&mirror->ref))
continue;
dev = &mirror->mirror_ds->id_node;
memcpy(&devinfo->dev_id, &dev->deviceid, NFS4_DEVICEID4_SIZE);

3
fs/nfs/flexfilelayout/flexfilelayout.h
View file

@ -13,6 +13,7 @@
#define FF_FLAGS_NO_IO_THRU_MDS 2
#define FF_FLAGS_NO_READ_IO 4
#include <linux/refcount.h>
#include "../pnfs.h"
/* XXX: Let's filter out insanely large mirror count for now to avoid oom
@ -81,7 +82,7 @@ struct nfs4_ff_layout_mirror {
nfs4_stateid stateid;
struct rpc_cred __rcu *ro_cred;
struct rpc_cred __rcu *rw_cred;
atomic_t ref;
refcount_t ref;
spinlock_t lock;
unsigned long flags;
struct nfs4_ff_layoutstat read_stat;