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Date: Tue, 22 Nov 2022 06:19:01 -0700 From: Jens Axboe <axboe@...nel.dk> To: Ammar Faizi <ammarfaizi2@...weeb.org> Cc: Stefan Roesch <shr@...kernel.io>, Facebook Kernel Team <kernel-team@...com>, Olivier Langlois <olivier@...llion01.com>, netdev Mailing List <netdev@...r.kernel.org>, io-uring Mailing List <io-uring@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org> Subject: Re: [PATCH v5 2/3] io_uring: add api to set / get napi configuration. On 11/22/22 6:13 AM, Ammar Faizi wrote: > On 11/22/22 2:46 AM, Jens Axboe wrote: >> On 11/21/22 12:14?PM, Stefan Roesch wrote: >>> +static int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg) >>> +{ >>> +#ifdef CONFIG_NET_RX_BUSY_POLL >>> + const struct io_uring_napi curr = { >>> + .busy_poll_to = ctx->napi_busy_poll_to, >>> + }; >>> + >>> + if (copy_to_user(arg, &curr, sizeof(curr))) >>> + return -EFAULT; >>> + >>> + WRITE_ONCE(ctx->napi_busy_poll_to, 0); >>> + return 0; >>> +#else >>> + return -EINVAL; >>> +#endif >>> +} >> >> Should probably check resv/pad here as well, maybe even the >> 'busy_poll_to' being zero? > > Jens, this function doesn't read from __user memory, it writes to > __user memory. > > @curr.resv and @curr.pad are on the kernel's stack. Both are already > implicitly initialized to zero by the partial struct initializer. Oh yes, guess I totally missed that we don't care about the value at all (just zero the target) and copy back the old values. -- Jens Axboe
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