Commit b7ac31b7 authored by Elena Reshetova's avatar Elena Reshetova Committed by David Sterba
Browse files

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: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 0700cea7

fs/btrfs/extent_io.c

+7 −7
Original line number Diff line number Diff line
@@ -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;

fs/btrfs/extent_io.h

+2 −1
Original line number Diff line number Diff line
@@ -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;

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