On Sun, 2015-11-08 at 00:50 +0900, Tetsuo Handa wrote:
> Commit 095dc8e0c3686d58 ("tcp: fix/cleanup inet_ehash_locks_alloc()")
> silently changed from kmalloc() to kmalloc_array(). The latter has
> overflow check whereas the former doesn't have.
>
> If nblocks * locksz might overflow, we need to do like
>
> - if (!hashinfo->ehash_locks && nblocks > SIZE_MAX / locksz)
> + if (!hashinfo->ehash_locks && nblocks > SIZE_MAX / locksz)
> hashinfo->ehash_locks = vmalloc(nblocks * locksz);
>
> because kmalloc_array() detects overflow and returns NULL.
> But if nblocks * locksz is guaranteed not to overflow, there is
> no need to use kmalloc_array().
>
> Since I assume it won't overflow, use kmalloc() than kmalloc_array().
>
> Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
> ---
> net/ipv4/inet_hashtables.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
> index ccc5980..8f4ab27 100644
> --- a/net/ipv4/inet_hashtables.c
> +++ b/net/ipv4/inet_hashtables.c
> @@ -648,8 +648,8 @@ int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
> /* no more locks than number of hash buckets */
> nblocks = min(nblocks, hashinfo->ehash_mask + 1);
>
> - hashinfo->ehash_locks = kmalloc_array(nblocks, locksz,
> - GFP_KERNEL |
> __GFP_NOWARN);
> + hashinfo->ehash_locks = kmalloc(nblocks * locksz,
> + GFP_KERNEL | __GFP_NOWARN);
> if (!hashinfo->ehash_locks)
> hashinfo->ehash_locks = vmalloc(nblocks * locksz);
>
I remember that my initial attempt had been to use size_t for nblocks,
but I realized roundup_pow_of_two() only accepted an 'unsigned long'
Then, presumably I just gave up.
I do not feel we should go back to kmalloc() just because
vmalloc_array() does not exist yet.
Maybe the following would clear things for you guys ?
If it is OK, please Tetsuo submit this patch formally.
Thanks !
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index ccc5980797fc..8f7c71e20089 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -638,15 +638,15 @@ EXPORT_SYMBOL_GPL(inet_hashinfo_init);
int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
{
unsigned int locksz = sizeof(spinlock_t);
- unsigned int i, nblocks = 1;
+ size_t i, nblocks = 1;
if (locksz != 0) {
/* allocate 2 cache lines or at least one spinlock per cpu */
- nblocks = max(2U * L1_CACHE_BYTES / locksz, 1U);
+ nblocks = max_t(size_t, 2 * L1_CACHE_BYTES / locksz, 1);
nblocks = roundup_pow_of_two(nblocks * num_possible_cpus());
/* no more locks than number of hash buckets */
- nblocks = min(nblocks, hashinfo->ehash_mask + 1);
+ nblocks = min_t(size_t, nblocks, hashinfo->ehash_mask + 1);
hashinfo->ehash_locks = kmalloc_array(nblocks, locksz,
GFP_KERNEL |
__GFP_NOWARN);
--
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