On Thu, Jan 30, 2025 at 04:44:42PM +0300, Alexey Dobriyan wrote:
> > -static inline unsigned int xfrm_replay_state_esn_len(struct xfrm_replay_state_esn *replay_esn)
> > +static inline size_t xfrm_replay_state_esn_len(struct xfrm_replay_state_esn *replay_esn)
> > {
> > - return sizeof(*replay_esn) + replay_esn->bmp_len * sizeof(__u32);
> > + return size_add(sizeof(*replay_esn), size_mul(replay_esn->bmp_len, sizeof(__u32)));
>
> Please don't do this.
>
> You can (and should!) make calculations and check for overflow at the
> same time. It's very efficient.
>
> > 1) Use size_add() and size_mul(). This change is necessary for 32bit systems.
>
> This bloats code on 32-bit.
>
I'm not sure I understand. On 32-bit systems a size_t and an unsigned
int are the same size. Did you mean to say 64-bit?
Declaring sizes as u32 leads to integer overflows like this one. If
you look at integer overflows with security implications there is a
5 to 1 ratio of bugs that only affect 32-bit vs bugs that affect
everything because it's just so much easier to overflow a 32-bit size.
aab98e2dbd64 ("ksmbd: fix integer overflows on 32 bit systems")
16ebb6f5b629 ("nfp: bpf: prevent integer overflow in nfp_bpf_event_output()")
09c4a6101532 ("rtc: tps6594: Fix integer overflow on 32bit systems")
55cf2f4b945f ("binfmt_flat: Fix integer overflow bug on 32 bit systems")
fbbd84af6ba7 ("chelsio/chtls: prevent potential integer overflow on 32bit")
bd96a3935e89 ("rdma/cxgb4: Prevent potential integer overflow on 32bit")
d0257e089d1b ("RDMA/uverbs: Prevent integer overflow issue")
3c63d8946e57 ("svcrdma: Address an integer overflow")
7f33b92e5b18 ("NFSD: Prevent a potential integer overflow")
> int len;
> if (__builtin_mul_overflow(replay_esn->bmp_len, 4, &len)) {
> return true;
> }
> if (__builtin_add_overflow(len, sizeof(*replay_esn), &len)) {
> return true;
> }
This is so ugly... :/ I'd prefer to just do open code the check at
that point.
static inline int xfrm_replay_state_esn_len(struct xfrm_replay_state_esn *replay_esn)
{
if (replay_esn->bmp_len > (INT_MAX - sizeof(*replay_esn)) / sizeof(__u32))
return -EINVAL;
return sizeof(*replay_esn) + replay_esn->bmp_len * sizeof(__u32);
}
regards,
dan carpenter
