btrfs: convert extent_state.refs from atomic_t to refcount_t

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 3649932e48d574015da2ce8212a72f3e04cf7269..174ffffd6d97c2170526e4966eee0fa7effb9f44 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -68,7 +68,7 @@ void btrfs_leak_debug_check(void)
                pr_err("BTRFS: state leak: start %llu end %llu state %u in tree %d refs %d\n",
                       state->start, state->end, state->state,
                       extent_state_in_tree(state),
-                      atomic_read(&state->refs));
+                      refcount_read(&state->refs));
                list_del(&state->leak_list);
                kmem_cache_free(extent_state_cache, state);
        }
@@ -238,7 +238,7 @@ static struct extent_state *alloc_extent_state(gfp_t mask)
        state->failrec = NULL;
        RB_CLEAR_NODE(&state->rb_node);
        btrfs_leak_debug_add(&state->leak_list, &states);
-       atomic_set(&state->refs, 1);
+       refcount_set(&state->refs, 1);
        init_waitqueue_head(&state->wq);
        trace_alloc_extent_state(state, mask, _RET_IP_);
        return state;
@@ -248,7 +248,7 @@ void free_extent_state(struct extent_state *state)
 {
        if (!state)
                return;
-       if (atomic_dec_and_test(&state->refs)) {
+       if (refcount_dec_and_test(&state->refs)) {
                WARN_ON(extent_state_in_tree(state));
                btrfs_leak_debug_del(&state->leak_list);
                trace_free_extent_state(state, _RET_IP_);
@@ -641,7 +641,7 @@ again:
                if (cached && extent_state_in_tree(cached) &&
                    cached->start <= start && cached->end > start) {
                        if (clear)
-                               atomic_dec(&cached->refs);
+                               refcount_dec(&cached->refs);
                        state = cached;
                        goto hit_next;
                }
@@ -793,7 +793,7 @@ process_node:
 
                if (state->state & bits) {
                        start = state->start;
-                       atomic_inc(&state->refs);
+                       refcount_inc(&state->refs);
                        wait_on_state(tree, state);
                        free_extent_state(state);
                        goto again;
@@ -834,7 +834,7 @@ static void cache_state_if_flags(struct extent_state *state,
        if (cached_ptr && !(*cached_ptr)) {
                if (!flags || (state->state & flags)) {
                        *cached_ptr = state;
-                       atomic_inc(&state->refs);
+                       refcount_inc(&state->refs);
                }
        }
 }
@@ -1538,7 +1538,7 @@ static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
                if (!found) {
                        *start = state->start;
                        *cached_state = state;
-                       atomic_inc(&state->refs);
+                       refcount_inc(&state->refs);
                }
                found++;
                *end = state->end;

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 3e4fad4a909d110d9283f979ccb9dec9a48c607c..8d2d6e4272d5fd6e235ab9d9e6efe8a474d7c8e2 100644 (file)
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -2,6 +2,7 @@
 #define __EXTENTIO__
 
 #include <linux/rbtree.h>
+#include <linux/refcount.h>
 #include "ulist.h"
 
 /* bits for the extent state */
@@ -143,7 +144,7 @@ struct extent_state {
 
        /* ADD NEW ELEMENTS AFTER THIS */
        wait_queue_head_t wq;
-       atomic_t refs;
+       refcount_t refs;
        unsigned state;
 
        struct io_failure_record *failrec;