bcachefs: Check for invalid bucket from bucket_gen(), gc_bucket()

Turn more asserts into proper recoverable error paths.

Reported-by: syzbot+246b47da27f8e7e7d6fb@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_background.c

@@ -741,6 +741,7 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 		       enum btree_iter_update_trigger_flags flags)
 {
 	struct bch_fs *c = trans->c;
+	struct printbuf buf = PRINTBUF;
 	int ret = 0;
 
 	struct bch_dev *ca = bch2_dev_bucket_tryget(c, new.k->p);
@@ -860,8 +861,14 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 		}
 
 		percpu_down_read(&c->mark_lock);
-		if (new_a->gen != old_a->gen)
-			*bucket_gen(ca, new.k->p.offset) = new_a->gen;
+		if (new_a->gen != old_a->gen) {
+			u8 *gen = bucket_gen(ca, new.k->p.offset);
+			if (unlikely(!gen)) {
+				percpu_up_read(&c->mark_lock);
+				goto invalid_bucket;
+			}
+			*gen = new_a->gen;
+		}
 
 		bch2_dev_usage_update(c, ca, old_a, new_a, journal_seq, false);
 		percpu_up_read(&c->mark_lock);
@@ -895,6 +902,11 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 
 		percpu_down_read(&c->mark_lock);
 		struct bucket *g = gc_bucket(ca, new.k->p.offset);
+		if (unlikely(!g)) {
+			percpu_up_read(&c->mark_lock);
+			goto invalid_bucket;
+		}
+		g->gen_valid	= 1;
 
 		bucket_lock(g);
 
@@ -910,8 +922,14 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 		percpu_up_read(&c->mark_lock);
 	}
 err:
+	printbuf_exit(&buf);
 	bch2_dev_put(ca);
 	return ret;
+invalid_bucket:
+	bch2_fs_inconsistent(c, "reference to invalid bucket\n  %s",
+			     (bch2_bkey_val_to_text(&buf, c, new.s_c), buf.buf));
+	ret = -EIO;
+	goto err;
 }
 
 /*

fs/bcachefs/btree_gc.c

@@ -874,6 +874,9 @@ static int bch2_alloc_write_key(struct btree_trans *trans,
 	const struct bch_alloc_v4 *old;
 	int ret;
 
+	if (!bucket_valid(ca, k.k->p.offset))
+		return 0;
+
 	old = bch2_alloc_to_v4(k, &old_convert);
 	gc = new = *old;
 
@@ -1005,12 +1008,14 @@ static int bch2_gc_alloc_start(struct bch_fs *c)
 				continue;
 			}
 
-			struct bch_alloc_v4 a_convert;
-			const struct bch_alloc_v4 *a = bch2_alloc_to_v4(k, &a_convert);
+			if (bucket_valid(ca, k.k->p.offset)) {
+				struct bch_alloc_v4 a_convert;
+				const struct bch_alloc_v4 *a = bch2_alloc_to_v4(k, &a_convert);
 
-			struct bucket *g = gc_bucket(ca, k.k->p.offset);
-			g->gen_valid	= 1;
-			g->gen		= a->gen;
+				struct bucket *g = gc_bucket(ca, k.k->p.offset);
+				g->gen_valid	= 1;
+				g->gen		= a->gen;
+			}
 			0;
 		})));
 	bch2_dev_put(ca);

fs/bcachefs/buckets.c

@@ -488,6 +488,17 @@ static int bch2_check_fix_ptr(struct btree_trans *trans,
 	}
 
 	struct bucket *g = PTR_GC_BUCKET(ca, &p.ptr);
+	if (!g) {
+		if (fsck_err(c, ptr_to_invalid_device,
+			     "pointer to invalid bucket on device %u\n"
+			     "while marking %s",
+			     p.ptr.dev,
+			     (printbuf_reset(&buf),
+			      bch2_bkey_val_to_text(&buf, c, k), buf.buf)))
+			*do_update = true;
+		goto out;
+	}
+
 	enum bch_data_type data_type = bch2_bkey_ptr_data_type(k, p, entry);
 
 	if (fsck_err_on(!g->gen_valid,
@@ -577,8 +588,8 @@ static int bch2_check_fix_ptr(struct btree_trans *trans,
 	if (p.has_ec) {
 		struct gc_stripe *m = genradix_ptr(&c->gc_stripes, p.ec.idx);
 
-		if (fsck_err_on(!m || !m->alive, c,
-				ptr_to_missing_stripe,
+		if (fsck_err_on(!m || !m->alive,
+				c, ptr_to_missing_stripe,
 				"pointer to nonexistent stripe %llu\n"
 				"while marking %s",
 				(u64) p.ec.idx,
@@ -586,8 +597,8 @@ static int bch2_check_fix_ptr(struct btree_trans *trans,
 				 bch2_bkey_val_to_text(&buf, c, k), buf.buf)))
 			*do_update = true;
 
-		if (fsck_err_on(m && m->alive && !bch2_ptr_matches_stripe_m(m, p), c,
-				ptr_to_incorrect_stripe,
+		if (fsck_err_on(m && m->alive && !bch2_ptr_matches_stripe_m(m, p),
+				c, ptr_to_incorrect_stripe,
 				"pointer does not match stripe %llu\n"
 				"while marking %s",
 				(u64) p.ec.idx,
@@ -1004,6 +1015,7 @@ static int bch2_trigger_pointer(struct btree_trans *trans,
 			enum btree_iter_update_trigger_flags flags)
 {
 	bool insert = !(flags & BTREE_TRIGGER_overwrite);
+	struct printbuf buf = PRINTBUF;
 	int ret = 0;
 
 	struct bch_fs *c = trans->c;
@@ -1036,6 +1048,13 @@ static int bch2_trigger_pointer(struct btree_trans *trans,
 	if (flags & BTREE_TRIGGER_gc) {
 		percpu_down_read(&c->mark_lock);
 		struct bucket *g = gc_bucket(ca, bucket.offset);
+		if (bch2_fs_inconsistent_on(!g, c, "reference to invalid bucket on device %u\n  %s",
+					    p.ptr.dev,
+					    (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
+			ret = -EIO;
+			goto err_unlock;
+		}
+
 		bucket_lock(g);
 		struct bch_alloc_v4 old = bucket_m_to_alloc(*g), new = old;
 		ret = __mark_pointer(trans, ca, k, &p.ptr, *sectors, bp.data_type, &new);
@@ -1044,10 +1063,12 @@ static int bch2_trigger_pointer(struct btree_trans *trans,
 			bch2_dev_usage_update(c, ca, &old, &new, 0, true);
 		}
 		bucket_unlock(g);
+err_unlock:
 		percpu_up_read(&c->mark_lock);
 	}
 err:
 	bch2_dev_put(ca);
+	printbuf_exit(&buf);
 	return ret;
 }
 
@@ -1335,10 +1356,11 @@ static int bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 			u64 b, enum bch_data_type data_type, unsigned sectors,
 			enum btree_iter_update_trigger_flags flags)
 {
-	int ret = 0;
-
 	percpu_down_read(&c->mark_lock);
 	struct bucket *g = gc_bucket(ca, b);
+	if (bch2_fs_inconsistent_on(!g, c, "reference to invalid bucket on device %u when marking metadata type %s",
+				    ca->dev_idx, bch2_data_type_str(data_type)))
+		goto err_unlock;
 
 	bucket_lock(g);
 	struct bch_alloc_v4 old = bucket_m_to_alloc(*g);
@@ -1347,29 +1369,27 @@ static int bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 			g->data_type != data_type, c,
 			"different types of data in same bucket: %s, %s",
 			bch2_data_type_str(g->data_type),
-			bch2_data_type_str(data_type))) {
-		ret = -EIO;
+			bch2_data_type_str(data_type)))
 		goto err;
-	}
 
 	if (bch2_fs_inconsistent_on((u64) g->dirty_sectors + sectors > ca->mi.bucket_size, c,
 			"bucket %u:%llu gen %u data type %s sector count overflow: %u + %u > bucket size",
 			ca->dev_idx, b, g->gen,
 			bch2_data_type_str(g->data_type ?: data_type),
-			g->dirty_sectors, sectors)) {
-		ret = -EIO;
+			g->dirty_sectors, sectors))
 		goto err;
-	}
 
 	g->data_type = data_type;
 	g->dirty_sectors += sectors;
 	struct bch_alloc_v4 new = bucket_m_to_alloc(*g);
+	bch2_dev_usage_update(c, ca, &old, &new, 0, true);
+	percpu_up_read(&c->mark_lock);
+	return 0;
 err:
 	bucket_unlock(g);
-	if (!ret)
-		bch2_dev_usage_update(c, ca, &old, &new, 0, true);
+err_unlock:
 	percpu_up_read(&c->mark_lock);
-	return ret;
+	return -EIO;
 }
 
 int bch2_trans_mark_metadata_bucket(struct btree_trans *trans,

fs/bcachefs/buckets.h

@@ -172,19 +172,22 @@ static inline int gen_after(u8 a, u8 b)
 	return r > 0 ? r : 0;
 }
 
-static inline u8 dev_ptr_stale_rcu(struct bch_dev *ca, const struct bch_extent_ptr *ptr)
+static inline int dev_ptr_stale_rcu(struct bch_dev *ca, const struct bch_extent_ptr *ptr)
 {
-	return gen_after(*bucket_gen(ca, PTR_BUCKET_NR(ca, ptr)), ptr->gen);
+	u8 *gen = bucket_gen(ca, PTR_BUCKET_NR(ca, ptr));
+	if (!gen)
+		return -1;
+	return gen_after(*gen, ptr->gen);
 }
 
 /**
  * dev_ptr_stale() - check if a pointer points into a bucket that has been
  * invalidated.
  */
-static inline u8 dev_ptr_stale(struct bch_dev *ca, const struct bch_extent_ptr *ptr)
+static inline int dev_ptr_stale(struct bch_dev *ca, const struct bch_extent_ptr *ptr)
 {
 	rcu_read_lock();
-	u8 ret = dev_ptr_stale_rcu(ca, ptr);
+	int ret = dev_ptr_stale_rcu(ca, ptr);
 	rcu_read_unlock();
 
 	return ret;

fs/bcachefs/ec.c

@@ -268,6 +268,7 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 {
 	struct bch_fs *c = trans->c;
 	const struct bch_extent_ptr *ptr = s.v->ptrs + ptr_idx;
+	struct printbuf buf = PRINTBUF;
 	int ret = 0;
 
 	struct bch_dev *ca = bch2_dev_tryget(c, ptr->dev);
@@ -289,6 +290,13 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 	if (flags & BTREE_TRIGGER_gc) {
 		percpu_down_read(&c->mark_lock);
 		struct bucket *g = gc_bucket(ca, bucket.offset);
+		if (bch2_fs_inconsistent_on(!g, c, "reference to invalid bucket on device %u\n  %s",
+					    ptr->dev,
+					    (bch2_bkey_val_to_text(&buf, c, s.s_c), buf.buf))) {
+			ret = -EIO;
+			goto err_unlock;
+		}
+
 		bucket_lock(g);
 		struct bch_alloc_v4 old = bucket_m_to_alloc(*g), new = old;
 		ret = __mark_stripe_bucket(trans, ca, s, ptr_idx, deleting, bucket, &new, flags);
@@ -297,10 +305,12 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 			bch2_dev_usage_update(c, ca, &old, &new, 0, true);
 		}
 		bucket_unlock(g);
+err_unlock:
 		percpu_up_read(&c->mark_lock);
 	}
 err:
 	bch2_dev_put(ca);
+	printbuf_exit(&buf);
 	return ret;
 }
 
@@ -714,10 +724,12 @@ static void ec_block_endio(struct bio *bio)
 			       bch2_blk_status_to_str(bio->bi_status)))
 		clear_bit(ec_bio->idx, ec_bio->buf->valid);
 
-	if (dev_ptr_stale(ca, ptr)) {
+	int stale = dev_ptr_stale(ca, ptr);
+	if (stale) {
 		bch_err_ratelimited(ca->fs,
-				    "error %s stripe: stale pointer after io",
-				    bio_data_dir(bio) == READ ? "reading from" : "writing to");
+				    "error %s stripe: stale/invalid pointer (%i) after io",
+				    bio_data_dir(bio) == READ ? "reading from" : "writing to",
+				    stale);
 		clear_bit(ec_bio->idx, ec_bio->buf->valid);
 	}
 
@@ -743,10 +755,12 @@ static void ec_block_io(struct bch_fs *c, struct ec_stripe_buf *buf,
 		return;
 	}
 
-	if (dev_ptr_stale(ca, ptr)) {
+	int stale = dev_ptr_stale(ca, ptr);
+	if (stale) {
 		bch_err_ratelimited(c,
-				    "error %s stripe: stale pointer",
-				    rw == READ ? "reading from" : "writing to");
+				    "error %s stripe: stale pointer (%i)",
+				    rw == READ ? "reading from" : "writing to",
+				    stale);
 		clear_bit(idx, buf->valid);
 		return;
 	}

fs/bcachefs/extents.c

@@ -137,7 +137,7 @@ int bch2_bkey_pick_read_device(struct bch_fs *c, struct bkey_s_c k,
 
 		struct bch_dev *ca = bch2_dev_rcu(c, p.ptr.dev);
 
-		if (p.ptr.cached && (!ca || dev_ptr_stale(ca, &p.ptr)))
+		if (p.ptr.cached && (!ca || dev_ptr_stale_rcu(ca, &p.ptr)))
 			continue;
 
 		f = failed ? dev_io_failures(failed, p.ptr.dev) : NULL;
@@ -999,7 +999,7 @@ bool bch2_extent_normalize(struct bch_fs *c, struct bkey_s k)
 	bch2_bkey_drop_ptrs(k, ptr,
 		ptr->cached &&
 		(ca = bch2_dev_rcu(c, ptr->dev)) &&
-		dev_ptr_stale_rcu(ca, ptr));
+		dev_ptr_stale_rcu(ca, ptr) > 0);
 	rcu_read_unlock();
 
 	return bkey_deleted(k.k);
@@ -1024,8 +1024,11 @@ void bch2_extent_ptr_to_text(struct printbuf *out, struct bch_fs *c, const struc
 			prt_str(out, " cached");
 		if (ptr->unwritten)
 			prt_str(out, " unwritten");
-		if (bucket_valid(ca, b) && dev_ptr_stale_rcu(ca, ptr))
+		int stale = dev_ptr_stale_rcu(ca, ptr);
+		if (stale > 0)
 			prt_printf(out, " stale");
+		else if (stale)
+			prt_printf(out, " invalid");
 	}
 	rcu_read_unlock();
 	--out->atomic;

fs/bcachefs/io_read.c

@@ -777,18 +777,32 @@ static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
 			     PTR_BUCKET_POS(ca, &ptr),
 			     BTREE_ITER_cached);
 
-	prt_printf(&buf, "Attempting to read from stale dirty pointer:\n");
-	printbuf_indent_add(&buf, 2);
+	u8 *gen = bucket_gen(ca, iter.pos.offset);
+	if (gen) {
 
-	bch2_bkey_val_to_text(&buf, c, k);
-	prt_newline(&buf);
+		prt_printf(&buf, "Attempting to read from stale dirty pointer:\n");
+		printbuf_indent_add(&buf, 2);
 
-	prt_printf(&buf, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
-
-	ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
-	if (!ret) {
+		bch2_bkey_val_to_text(&buf, c, k);
 		prt_newline(&buf);
+
+		prt_printf(&buf, "memory gen: %u", *gen);
+
+		ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
+		if (!ret) {
+			prt_newline(&buf);
+			bch2_bkey_val_to_text(&buf, c, k);
+		}
+	} else {
+		prt_printf(&buf, "Attempting to read from invalid bucket %llu:%llu:\n",
+			   iter.pos.inode, iter.pos.offset);
+		printbuf_indent_add(&buf, 2);
+
+		prt_printf(&buf, "first bucket %u nbuckets %llu\n",
+			   ca->mi.first_bucket, ca->mi.nbuckets);
+
 		bch2_bkey_val_to_text(&buf, c, k);
+		prt_newline(&buf);
 	}
 
 	bch2_fs_inconsistent(c, "%s", buf.buf);

fs/bcachefs/io_write.c

@@ -1220,7 +1220,7 @@ static void bch2_nocow_write(struct bch_write_op *op)
 	DARRAY_PREALLOCATED(struct bucket_to_lock, 3) buckets;
 	u32 snapshot;
 	struct bucket_to_lock *stale_at;
-	int ret;
+	int stale, ret;
 
 	if (op->flags & BCH_WRITE_MOVE)
 		return;
@@ -1299,7 +1299,8 @@ static void bch2_nocow_write(struct bch_write_op *op)
 						 BUCKET_NOCOW_LOCK_UPDATE);
 
 			rcu_read_lock();
-			bool stale = gen_after(*bucket_gen(ca, i->b.offset), i->gen);
+			u8 *gen = bucket_gen(ca, i->b.offset);
+			stale = !gen ? -1 : gen_after(*gen, i->gen);
 			rcu_read_unlock();
 
 			if (unlikely(stale)) {
@@ -1380,8 +1381,18 @@ static void bch2_nocow_write(struct bch_write_op *op)
 			break;
 	}
 
-	/* We can retry this: */
-	ret = -BCH_ERR_transaction_restart;
+	struct printbuf buf = PRINTBUF;
+	if (bch2_fs_inconsistent_on(stale < 0, c,
+				    "pointer to invalid bucket in nocow path on device %llu\n  %s",
+				    stale_at->b.inode,
+				    (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
+		ret = -EIO;
+	} else {
+		/* We can retry this: */
+		ret = -BCH_ERR_transaction_restart;
+	}
+	printbuf_exit(&buf);
+
 	goto err_get_ioref;
 }