bcachefs: Prefer struct_size over open coded arithmetic

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].

As the "op" variable is a pointer to "struct promote_op" and this
structure ends in a flexible array:

struct promote_op {
	[...]
	struct bio_vec bi_inline_vecs[];
};

and the "t" variable is a pointer to "struct journal_seq_blacklist_table"
and this structure also ends in a flexible array:

struct journal_seq_blacklist_table {
	[...]
	struct journal_seq_blacklist_table_entry {
		u64		start;
		u64		end;
		bool		dirty;
	}			entries[];
};

the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the argument "size + size * count" in the
kzalloc() functions.

This way, the code is more readable and safer.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Erick Archer <erick.archer@gmx.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index 3c574d8873a1e209dc7f7f48faacf9928f8a1272..8a556e6d1ab6f2080342a0f232c94cf160600fe1 100644 (file)
--- a/fs/bcachefs/io_read.c
+++ b/fs/bcachefs/io_read.c
@@ -174,7 +174,7 @@ static struct promote_op *__promote_alloc(struct btree_trans *trans,
        if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_promote))
                return ERR_PTR(-BCH_ERR_nopromote_no_writes);
 
-       op = kzalloc(sizeof(*op) + sizeof(struct bio_vec) * pages, GFP_KERNEL);
+       op = kzalloc(struct_size(op, bi_inline_vecs, pages), GFP_KERNEL);
        if (!op) {
                ret = -BCH_ERR_nopromote_enomem;
                goto err;

diff --git a/fs/bcachefs/journal_seq_blacklist.c b/fs/bcachefs/journal_seq_blacklist.c
index 5acc1276675c18362e42c342b9be60fa003ebeaa..b5303874fc35b33e5e6ac3878a03af8ab1a882be 100644 (file)
--- a/fs/bcachefs/journal_seq_blacklist.c
+++ b/fs/bcachefs/journal_seq_blacklist.c
@@ -141,8 +141,7 @@ int bch2_blacklist_table_initialize(struct bch_fs *c)
        if (!bl)
                return 0;
 
-       t = kzalloc(sizeof(*t) + sizeof(t->entries[0]) * nr,
-                   GFP_KERNEL);
+       t = kzalloc(struct_size(t, entries, nr), GFP_KERNEL);
        if (!t)
                return -BCH_ERR_ENOMEM_blacklist_table_init;