From 81a090b9975b89ca15e71d0bca945358f6fe7696 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:34 +0300 Subject: [PATCH] fs, nfs: convert nfs4_ff_layout_mirror.ref from atomic_t to refcount_t 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 Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Anna Schumaker --- fs/nfs/flexfilelayout/flexfilelayout.c | 8 ++++---- fs/nfs/flexfilelayout/flexfilelayout.h | 3 ++- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c index b0fa83a607541..ff55a0a1b2e8a 100644 --- a/fs/nfs/flexfilelayout/flexfilelayout.c +++ b/fs/nfs/flexfilelayout/flexfilelayout.c @@ -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); diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h index 98b34c9b0564b..ca35426ac3b4a 100644 --- a/fs/nfs/flexfilelayout/flexfilelayout.h +++ b/fs/nfs/flexfilelayout/flexfilelayout.h @@ -13,6 +13,7 @@ #define FF_FLAGS_NO_IO_THRU_MDS 2 #define FF_FLAGS_NO_READ_IO 4 +#include #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; -- 2.39.5