2024-02-24 14:59:59

by Erick Archer

[permalink] [raw]
Subject: [PATCH] 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[];
};

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() function.

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 [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <[email protected]>
---
fs/bcachefs/io_read.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index dce136cd2271..01beab55c6b3 100644
--- 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;
--
2.25.1