2024-03-10 11:03:04

by Erick Archer

Subject: [PATCH v2] 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 [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <[email protected]>
---
Changes in v2:
- Merge the two patches in one single patch (Kent Overstreet).

Previous versions:
v1 -> https://lore.kernel.org/linux-hardening/[email protected]/
v1 -> https://lore.kernel.org/linux-hardening/[email protected]/
---
fs/bcachefs/io_read.c | 2 +-
fs/bcachefs/journal_seq_blacklist.c | 3 +--
2 files changed, 2 insertions(+), 3 deletions(-)

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;
diff --git a/fs/bcachefs/journal_seq_blacklist.c b/fs/bcachefs/journal_seq_blacklist.c
index 024c9b1b323f..2c2490aa15fe 100644
--- a/fs/bcachefs/journal_seq_blacklist.c
+++ b/fs/bcachefs/journal_seq_blacklist.c
@@ -165,8 +165,7 @@ 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;

--
2.25.1

2024-03-10 19:42:16

by Kent Overstreet

Subject: Re: [PATCH v2] bcachefs: Prefer struct_size over open coded arithmetic

On Sun, Mar 10, 2024 at 12:02:26PM +0100, Erick Archer wrote:
> 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 [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Erick Archer <[email protected]>

applied