linux-hardening - [PATCH] bcachefs: Annotate bch_replicas_entry_{v0,v1} with __counted

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Message-ID: <20240825133601.24036-2-thorsten.blum@toblux.com>
Date: Sun, 25 Aug 2024 15:36:02 +0200
From: Thorsten Blum <thorsten.blum@...lux.com>
To: kent.overstreet@...ux.dev,
	kees@...nel.org,
	gustavoars@...nel.org
Cc: linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	Thorsten Blum <thorsten.blum@...lux.com>
Subject: [PATCH] bcachefs: Annotate bch_replicas_entry_{v0,v1} with __counted_by()

Add the __counted_by compiler attribute to the flexible array members
devs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Increment nr_devs before adding a new device to the devs array and
adjust the array indexes accordingly.

In bch2_journal_read(), explicitly set nr_devs to 0.

Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
---
 fs/bcachefs/buckets.c         | 3 ++-
 fs/bcachefs/journal_io.c      | 3 ++-
 fs/bcachefs/replicas.c        | 6 +++---
 fs/bcachefs/replicas_format.h | 4 ++--
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/bcachefs/buckets.c b/fs/bcachefs/buckets.c
index be2bbd248631..1e6badf9ddd2 100644
--- a/fs/bcachefs/buckets.c
+++ b/fs/bcachefs/buckets.c
@@ -740,7 +740,8 @@ static int __trigger_extent(struct btree_trans *trans,
 				return ret;
 		} else if (!p.has_ec) {
 			replicas_sectors       += disk_sectors;
-			acc_replicas_key.replicas.devs[acc_replicas_key.replicas.nr_devs++] = p.ptr.dev;
+			acc_replicas_key.replicas.nr_devs++;
+			acc_replicas_key.replicas.devs[acc_replicas_key.replicas.nr_devs - 1] = p.ptr.dev;
 		} else {
 			ret = bch2_trigger_stripe_ptr(trans, k, p, data_type, disk_sectors, flags);
 			if (ret)
diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c
index 7664b68e6a15..d1bd883c2c55 100644
--- a/fs/bcachefs/journal_io.c
+++ b/fs/bcachefs/journal_io.c
@@ -1353,6 +1353,7 @@ int bch2_journal_read(struct bch_fs *c,
 	genradix_for_each(&c->journal_entries, radix_iter, _i) {
 		struct bch_replicas_padded replicas = {
 			.e.data_type = BCH_DATA_journal,
+			.e.nr_devs = 0,
 			.e.nr_required = 1,
 		};
 
@@ -1379,7 +1380,7 @@ int bch2_journal_read(struct bch_fs *c,
 			goto err;
 
 		darray_for_each(i->ptrs, ptr)
-			replicas.e.devs[replicas.e.nr_devs++] = ptr->dev;
+			replicas.e.devs[++replicas.e.nr_devs - 1] = ptr->dev;
 
 		bch2_replicas_entry_sort(&replicas.e);
 
diff --git a/fs/bcachefs/replicas.c b/fs/bcachefs/replicas.c
index 1223b710755d..90d9b7d761bc 100644
--- a/fs/bcachefs/replicas.c
+++ b/fs/bcachefs/replicas.c
@@ -122,7 +122,7 @@ static void extent_to_replicas(struct bkey_s_c k,
 			continue;
 
 		if (!p.has_ec)
-			r->devs[r->nr_devs++] = p.ptr.dev;
+			r->devs[++r->nr_devs - 1] = p.ptr.dev;
 		else
 			r->nr_required = 0;
 	}
@@ -139,7 +139,7 @@ static void stripe_to_replicas(struct bkey_s_c k,
 	for (ptr = s.v->ptrs;
 	     ptr < s.v->ptrs + s.v->nr_blocks;
 	     ptr++)
-		r->devs[r->nr_devs++] = ptr->dev;
+		r->devs[++r->nr_devs - 1] = ptr->dev;
 }
 
 void bch2_bkey_to_replicas(struct bch_replicas_entry_v1 *e,
@@ -180,7 +180,7 @@ void bch2_devlist_to_replicas(struct bch_replicas_entry_v1 *e,
 	e->nr_required	= 1;
 
 	darray_for_each(devs, i)
-		e->devs[e->nr_devs++] = *i;
+		e->devs[++e->nr_devs - 1] = *i;
 
 	bch2_replicas_entry_sort(e);
 }
diff --git a/fs/bcachefs/replicas_format.h b/fs/bcachefs/replicas_format.h
index b97208195d06..d2e080d0ecb7 100644
--- a/fs/bcachefs/replicas_format.h
+++ b/fs/bcachefs/replicas_format.h
@@ -5,7 +5,7 @@
 struct bch_replicas_entry_v0 {
 	__u8			data_type;
 	__u8			nr_devs;
-	__u8			devs[];
+	__u8			devs[] __counted_by(nr_devs);
 } __packed;
 
 struct bch_sb_field_replicas_v0 {
@@ -17,7 +17,7 @@ struct bch_replicas_entry_v1 {
 	__u8			data_type;
 	__u8			nr_devs;
 	__u8			nr_required;
-	__u8			devs[];
+	__u8			devs[] __counted_by(nr_devs);
 } __packed;
 
 struct bch_sb_field_replicas {
-- 
2.46.0