On Sat, Sep 18, 2021 at 05:05:00PM +0200, 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, switch to flexible array member in the struct attribute_set_obj and > refactor the code accordingly to use the struct_size() helper instead of > the argument "size + count * size" in the kzalloc() function. > > [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/platform/x86/thinkpad_acpi.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c > index 50ff04c84650..ed0b01ead796 100644 > --- a/drivers/platform/x86/thinkpad_acpi.c > +++ b/drivers/platform/x86/thinkpad_acpi.c > @@ -1008,7 +1008,7 @@ struct attribute_set { > > struct attribute_set_obj { > struct attribute_set s; > - struct attribute *a; > + struct attribute *a[]; > } __attribute__((packed)); Whoa. I have so many questions... :) > > static struct attribute_set *create_attr_set(unsigned int max_members, > @@ -1020,13 +1020,11 @@ static struct attribute_set *create_attr_set(unsigned int max_members, > return NULL; > > /* Allocates space for implicit NULL at the end too */ > - sobj = kzalloc(sizeof(struct attribute_set_obj) + > - max_members * sizeof(struct attribute *), > - GFP_KERNEL); > + sobj = kzalloc(struct_size(sobj, a, max_members + 1), GFP_KERNEL); Whoa, this needs a lot more detail in the changelog if this is actually correct. The original code doesn't seem to match the comment? (Where is the +1?) So is this also a bug-fix? (I see the caller uses +2? Why? It seems to be using each of hotkey_attributes, plus 1 more attr, plus a final NULL?) > if (!sobj) > return NULL; > sobj->s.max_members = max_members; > - sobj->s.group.attrs = &sobj->a; > + sobj->s.group.attrs = sobj->a; > sobj->s.group.name = name; The caller also never sets a name? Why is struct attribute_set_obj marked as __packed? > > return &sobj->s; > -- > 2.25.1 > -- Kees Cook
