On Tue, 29 Oct 2019 16:43:07 +0100, Björn Töpel wrote:

From: Björn Töpel <redacted>

The functions bpf_map_area_alloc() and bpf_map_charge_init() prior
this commit passed the size parameter as size_t. In this commit this
is changed to u64.

All users of these functions avoid size_t overflows on 32-bit systems,
by explicitly using u64 when calculating the allocation size and
memory charge cost. However, since the result was narrowed by the
size_t when passing size and cost to the functions, the overflow
handling was in vain.

Instead of changing all call sites to size_t and handle overflow at
the call site, the parameter is changed to u64 and checked in the
functions above.

Fixes: d407bd25a204 ("bpf: don't trigger OOM killer under pressure with map alloc")
Fixes: c85d69135a91 ("bpf: move memory size checks to bpf_map_charge_init()")
Signed-off-by: Björn Töpel <redacted>

Okay, I guess that's the smallest change we can make here.

I'd prefer we went the way of using the standard overflow handling the
kernel has, rather than proliferating this u64 + U32_MAX comparison
stuff. But it's hard to argue with the patch length in light of the
necessary backports..

Reviewed-by: Jakub Kicinski <redacted>