As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.
So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kmalloc() and kzalloc() functions.
Also, take the opportunity to refactor the memcpy() calls to use the
struct_size() and flex_array_size() helpers.
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
Signed-off-by: Len Baker <[email protected]>
---
lib/assoc_array.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index 04c98799c3ba..079c72e26493 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -741,8 +741,7 @@ static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
- new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
- keylen * sizeof(unsigned long), GFP_KERNEL);
+ new_s0 = kzalloc(struct_size(new_s0, index_key, keylen), GFP_KERNEL);
if (!new_s0)
return false;
edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
@@ -849,8 +848,8 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
- new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
- keylen * sizeof(unsigned long), GFP_KERNEL);
+ new_s0 = kzalloc(struct_size(new_s0, index_key, keylen),
+ GFP_KERNEL);
if (!new_s0)
return false;
edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
@@ -864,7 +863,7 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
new_n0->parent_slot = 0;
memcpy(new_s0->index_key, shortcut->index_key,
- keylen * sizeof(unsigned long));
+ flex_array_size(new_s0, index_key, keylen));
blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
@@ -899,8 +898,8 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
- new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
- keylen * sizeof(unsigned long), GFP_KERNEL);
+ new_s1 = kzalloc(struct_size(new_s1, index_key, keylen),
+ GFP_KERNEL);
if (!new_s1)
return false;
edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
@@ -913,7 +912,7 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
memcpy(new_s1->index_key, shortcut->index_key,
- keylen * sizeof(unsigned long));
+ flex_array_size(new_s1, index_key, keylen));
edit->set[1].ptr = &side->back_pointer;
edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
@@ -1490,13 +1489,12 @@ int assoc_array_gc(struct assoc_array *array,
shortcut = assoc_array_ptr_to_shortcut(cursor);
keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
- new_s = kmalloc(sizeof(struct assoc_array_shortcut) +
- keylen * sizeof(unsigned long), GFP_KERNEL);
+ new_s = kmalloc(struct_size(new_s, index_key, keylen),
+ GFP_KERNEL);
if (!new_s)
goto enomem;
pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
- memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) +
- keylen * sizeof(unsigned long)));
+ memcpy(new_s, shortcut, struct_size(new_s, index_key, keylen));
new_s->back_pointer = new_parent;
new_s->parent_slot = shortcut->parent_slot;
*new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
--
2.25.1
On 9/19/21 06:09, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + count * size" in the kmalloc() and kzalloc() functions.
>
> Also, take the opportunity to refactor the memcpy() calls to use the
> struct_size() and flex_array_size() helpers.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <[email protected]>
Reviewed-by: Gustavo A. R. Silva <[email protected]>
I'll add this to my -next tree.
Thanks
--
Gustavo
> ---
> lib/assoc_array.c | 22 ++++++++++------------
> 1 file changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/lib/assoc_array.c b/lib/assoc_array.c
> index 04c98799c3ba..079c72e26493 100644
> --- a/lib/assoc_array.c
> +++ b/lib/assoc_array.c
> @@ -741,8 +741,7 @@ static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
> keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
> keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
>
> - new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
> - keylen * sizeof(unsigned long), GFP_KERNEL);
> + new_s0 = kzalloc(struct_size(new_s0, index_key, keylen), GFP_KERNEL);
> if (!new_s0)
> return false;
> edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
> @@ -849,8 +848,8 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
> keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
> keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
>
> - new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
> - keylen * sizeof(unsigned long), GFP_KERNEL);
> + new_s0 = kzalloc(struct_size(new_s0, index_key, keylen),
> + GFP_KERNEL);
> if (!new_s0)
> return false;
> edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
> @@ -864,7 +863,7 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
> new_n0->parent_slot = 0;
>
> memcpy(new_s0->index_key, shortcut->index_key,
> - keylen * sizeof(unsigned long));
> + flex_array_size(new_s0, index_key, keylen));
>
> blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
> pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
> @@ -899,8 +898,8 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
> keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
> keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
>
> - new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
> - keylen * sizeof(unsigned long), GFP_KERNEL);
> + new_s1 = kzalloc(struct_size(new_s1, index_key, keylen),
> + GFP_KERNEL);
> if (!new_s1)
> return false;
> edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
> @@ -913,7 +912,7 @@ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
> new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
>
> memcpy(new_s1->index_key, shortcut->index_key,
> - keylen * sizeof(unsigned long));
> + flex_array_size(new_s1, index_key, keylen));
>
> edit->set[1].ptr = &side->back_pointer;
> edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
> @@ -1490,13 +1489,12 @@ int assoc_array_gc(struct assoc_array *array,
> shortcut = assoc_array_ptr_to_shortcut(cursor);
> keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
> keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
> - new_s = kmalloc(sizeof(struct assoc_array_shortcut) +
> - keylen * sizeof(unsigned long), GFP_KERNEL);
> + new_s = kmalloc(struct_size(new_s, index_key, keylen),
> + GFP_KERNEL);
> if (!new_s)
> goto enomem;
> pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
> - memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) +
> - keylen * sizeof(unsigned long)));
> + memcpy(new_s, shortcut, struct_size(new_s, index_key, keylen));
> new_s->back_pointer = new_parent;
> new_s->parent_slot = shortcut->parent_slot;
> *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
> --
> 2.25.1
>