On Fri, Dec 17, 2021 at 09:16:19AM +0000, Steven Price wrote: > On 17/12/2021 09:10, Dan Carpenter wrote: > > On Fri, Dec 17, 2021 at 08:55:50AM +0000, Steven Price wrote: > >> However this one is harder to fix without setting an arbitrary cap on > >> the number of BOs during a sumbit. I'm not sure how other drivers handle > >> this - the ones I've looked at so far all have the same issue. There's > >> obviously the list that Dan already sent, but e.g. msm has the same bug > >> in msm_gem_submit.c:submit_create() with an amusing bug where the check > >> for (sz > SIZE_MAX) will never hit, although the call is to kzalloc() so > >> large allocations are going to fail anyway. > > > > sz is u64 and SIZE_MAX is ULONG_MAX so the (sz > SIZE_MAX) condition > > does work to prevent an integer overflow on 32bit systems. But it's not > > beautiful. > > sz is the result of struct_size() which returns a size_t, and SIZE_MAX > in case of an overflow. Correct. > However the check is *greater than* SIZE_MAX > which will never occur even on 32 bit systems. You've missed a part. We add ((u64)nr_cmds * sizeof(submit->cmd[0])) to SIZE_MAX. If nr_cmds is zero then, whatever, the kzmalloc() will fail. No big deal. But if it's non-zero then "sz" is larger than SIZE_MAX and we allocate a smaller buffer than expected leading to memory corruption. Btw, it turns out that I had a hand in writing that check so hooray for me. :) #HoorayForMe regards, dan carpenter
