On 11/07, Mina Almasry wrote:
> Exit early if we're freeing more than 1024 frags, to prevent
> looping too long.
>
> Also minor code cleanups:
> - Flip checks to reduce indentation.
> - Use sizeof(*tokens) everywhere for consistentcy.
>
> Cc: Yi Lai <yi1.lai@xxxxxxxxxxxxxxx>
> Cc: Stanislav Fomichev <sdf@xxxxxxxxxxx>
> Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
>
> ---
>
> v2:
> - Retain token check to prevent allocation of too much memory.
> - Exit early instead of pre-checking in a loop so that we don't penalize
> well behaved applications (sdf)
>
> ---
> net/core/sock.c | 42 ++++++++++++++++++++++++------------------
> 1 file changed, 24 insertions(+), 18 deletions(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 039be95c40cf..da50df485090 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1052,32 +1052,34 @@ static int sock_reserve_memory(struct sock *sk, int bytes)
>
> #ifdef CONFIG_PAGE_POOL
>
> -/* This is the number of tokens that the user can SO_DEVMEM_DONTNEED in
> - * 1 syscall. The limit exists to limit the amount of memory the kernel
> - * allocates to copy these tokens.
> +/* This is the number of tokens and frags that the user can SO_DEVMEM_DONTNEED
> + * in 1 syscall. The limit exists to limit the amount of memory the kernel
> + * allocates to copy these tokens, and to prevent looping over the frags for
> + * too long.
> */
> #define MAX_DONTNEED_TOKENS 128
> +#define MAX_DONTNEED_FRAGS 1024
>
> static noinline_for_stack int
> sock_devmem_dontneed(struct sock *sk, sockptr_t optval, unsigned int optlen)
> {
> unsigned int num_tokens, i, j, k, netmem_num = 0;
> struct dmabuf_token *tokens;
> + int ret = 0, num_frags = 0;
> netmem_ref netmems[16];
> - int ret = 0;
>
> if (!sk_is_tcp(sk))
> return -EBADF;
>
> - if (optlen % sizeof(struct dmabuf_token) ||
> + if (optlen % sizeof(*tokens) ||
> optlen > sizeof(*tokens) * MAX_DONTNEED_TOKENS)
> return -EINVAL;
>
[..]
> - tokens = kvmalloc_array(optlen, sizeof(*tokens), GFP_KERNEL);
Oh, so we currently allocate optlen*8? This is a sneaky fix :-p
> + num_tokens = optlen / sizeof(*tokens);
> + tokens = kvmalloc_array(num_tokens, sizeof(*tokens), GFP_KERNEL);
> if (!tokens)
> return -ENOMEM;
>
> - num_tokens = optlen / sizeof(struct dmabuf_token);
> if (copy_from_sockptr(tokens, optval, optlen)) {
> kvfree(tokens);
> return -EFAULT;
> @@ -1086,24 +1088,28 @@ sock_devmem_dontneed(struct sock *sk, sockptr_t optval, unsigned int optlen)
> xa_lock_bh(&sk->sk_user_frags);
> for (i = 0; i < num_tokens; i++) {
> for (j = 0; j < tokens[i].token_count; j++) {
[..]
> + if (++num_frags > MAX_DONTNEED_FRAGS)
> + goto frag_limit_reached;
> +
nit: maybe reuse existing ret (and rename it to num_frags) instead of
introducing new num_frags? Both variables now seem to track the same
number.
