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. In this case these are not actually dynamic sizes: all the operands involved in the calculation are constant values. However it is better to refactor them anyway, just to keep the open-coded math idiom out of code. So, add at the end of the struct i915_syncmap a union with two flexible array members (these arrays share the same memory layout). This is possible using the new DECLARE_FLEX_ARRAY macro. And then, 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 __sync_seqno and __sync_child making them more readable. This code was detected with the help of Coccinelle and audited and fixed manually. [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments Signed-off-by: Len Baker <len.baker@xxxxxxx> --- drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_syncmap.c b/drivers/gpu/drm/i915/i915_syncmap.c index 60404dbb2e9f..a8d35491d05a 100644 --- a/drivers/gpu/drm/i915/i915_syncmap.c +++ b/drivers/gpu/drm/i915/i915_syncmap.c @@ -82,6 +82,10 @@ struct i915_syncmap { * struct i915_syncmap *child[KSYNCMAP]; * }; */ + union { + DECLARE_FLEX_ARRAY(u32, seqno); + DECLARE_FLEX_ARRAY(struct i915_syncmap *, child); + }; }; /** @@ -99,13 +103,13 @@ void i915_syncmap_init(struct i915_syncmap **root) static inline u32 *__sync_seqno(struct i915_syncmap *p) { GEM_BUG_ON(p->height); - return (u32 *)(p + 1); + return p->seqno; } static inline struct i915_syncmap **__sync_child(struct i915_syncmap *p) { GEM_BUG_ON(!p->height); - return (struct i915_syncmap **)(p + 1); + return p->child; } static inline unsigned int @@ -200,7 +204,7 @@ __sync_alloc_leaf(struct i915_syncmap *parent, u64 id) { struct i915_syncmap *p; - p = kmalloc(sizeof(*p) + KSYNCMAP * sizeof(u32), GFP_KERNEL); + p = kmalloc(struct_size(p, seqno, KSYNCMAP), GFP_KERNEL); if (unlikely(!p)) return NULL; @@ -282,7 +286,7 @@ static noinline int __sync_set(struct i915_syncmap **root, u64 id, u32 seqno) unsigned int above; /* Insert a join above the current layer */ - next = kzalloc(sizeof(*next) + KSYNCMAP * sizeof(next), + next = kzalloc(struct_size(next, child, KSYNCMAP), GFP_KERNEL); if (unlikely(!next)) return -ENOMEM; -- 2.25.1
