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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>
This commit is contained in:
Elena Reshetova 2017-03-03 10:55:19 +02:00 committed by David Sterba
parent 0700cea7c8
commit b7ac31b7b2
2 changed files with 9 additions and 8 deletions
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14
fs/btrfs/extent_io.c
View File

@ -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;

3
fs/btrfs/extent_io.h
View File

@ -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;