slab: krealloc with GFP

Joe Perches

2013-09-10 23:51:01 UTC

ping?

Post by Joe Perches
This sequence can return non-zeroed memory from the
padding area of the original allocation.
ptr = kzalloc(foo, GFP_KERNEL);
if (!ptr)
...
new_ptr = krealloc(ptr, foo + bar, GFP_KERNEL | __GFP_ZERO);
If the realloc size is within the first actual allocation
then the additional memory is not zeroed.
If the realloc size is not within the original allocation
size, any non-zeroed padding from the original allocation
is overwriting newly allocated zeroed memory.
Maybe someone more familiar with the alignment & padding can
add the proper memset(,0,) for the __GFP_ZERO cases and also
optimize kmalloc_track_caller to not use __GFP_ZERO, memcpy
the current (non padded) size and zero the newly returned
remainder if necessary.
from: mm/util.c
---------------------------
static __always_inline void *__do_krealloc(const void *p, size_t new_size,
gfp_t flags)
{
void *ret;
size_t ks = 0;
if (p)
ks = ksize(p);
if (ks >= new_size)
return (void *)p;
ret = kmalloc_track_caller(new_size, flags);
if (ret && p)
memcpy(ret, p, ks);
return ret;
}

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