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[209.132.180.67]) by mx.google.com with ESMTP id s84si5706740oib.83.2020.03.22.08.47.42; Sun, 22 Mar 2020 08:48:11 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-bluetooth-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=A4TpLnb+; spf=pass (google.com: best guess record for domain of linux-bluetooth-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-bluetooth-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725971AbgCVPrk (ORCPT + 99 others); Sun, 22 Mar 2020 11:47:40 -0400 Received: from mail-wm1-f66.google.com ([209.85.128.66]:50202 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725970AbgCVPrk (ORCPT ); Sun, 22 Mar 2020 11:47:40 -0400 Received: by mail-wm1-f66.google.com with SMTP id d198so5911193wmd.0; Sun, 22 Mar 2020 08:47:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=mmvl+SIl3Wyrd13xcSYtqks/rpSJ/1G5aSjV1RSqo6c=; b=A4TpLnb+dBsAR01rHHiMIK/HzyG5hhrZHhqdkzexwDABywiGFj/MG/K8JNg0n/G5xF ndlwbLIskoRqEWn0H9btV0XGjOxwU43KGLkSn7mFY331Mi9Vvt9ujgKT6akepfszSdvm F3TPM1oWh8+6wwEj62Ym4EQxONjTdxQzcagCAJGT9QWXSy2b3GYSg5/KtraVw4nAZ/2P HeklPzB7roBOd1Nh0f57KtumWoDGuAOMpJ2Z/2o83bPxQel4S76kainB+A49rPNu6+qL Dx5gv3vSWDQGc5nSoJJ/sKlAONruGO9zyFEeIz6czB/BNYHisPMARRKFoVPPerVbWLAt HxYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=mmvl+SIl3Wyrd13xcSYtqks/rpSJ/1G5aSjV1RSqo6c=; b=T07oX94d2nN9I2yucowlLIAMsFP5hfCv6xXIvOWGLFE9ZA3OI6LyZ3zRJtevO1aJ/L m+Ru7B9Ea1DjgQOGwRjiXwTULuL5iSsavIKox20yhupub06u88vOiMUBrjSLRaNYEDU1 3JgfqHZEm2HW88rN7ztSyhrkqaMIuqNukGqbL0xDT5WnnGtor9PXIaSmpdzfacnADckj vpd2UgQf4O1r/kG7lYhfnpGSFsjpOmMAjiddFKlDFI9H9iTKNop8se3n4fpAYpYiKGUg CwZ5VK8XCrfdvwqAgwHrbMl0IXIsIG14zYBGwBQ/j87Q3Hv9YTFdPvV5pQ4MgHtA2rcw FBVw== X-Gm-Message-State: ANhLgQ3fYO15mBCK9EcytfjQD12qe64FzBpxe+kkNOQzcpSJBdXEUKcs W/gRPE6n/As+j3+poMdC5WM= X-Received: by 2002:a1c:9ac2:: with SMTP id c185mr21793859wme.45.1584892056507; Sun, 22 Mar 2020 08:47:36 -0700 (PDT) Received: from pali ([2a02:2b88:2:1::5cc6:2f]) by smtp.gmail.com with ESMTPSA id o14sm3226935wmh.22.2020.03.22.08.47.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Mar 2020 08:47:35 -0700 (PDT) Date: Sun, 22 Mar 2020 16:47:34 +0100 From: Pali =?utf-8?B?Um9ow6Fy?= To: Dmitry Torokhov Cc: Abhishek Pandit-Subedi , linux-input@vger.kernel.org, Bluez mailing list , Luiz Augusto von Dentz , Enric Balletbo i Serra , LKML , Thomas Gleixner , Logan Gunthorpe , Andrey Smirnov , Kirill Smelkov Subject: Re: [PATCH] Input: uinput - Add UI_SET_UNIQ ioctl handler Message-ID: <20200322154734.mquwgzc63nzddiy5@pali> References: <20191202193628.GI50317@dtor-ws> <20191202230947.ld5ibnczdpkekfcm@pali> <20191203173821.4u6uzxeaqnt3gyz3@pali> <20191203191112.GJ50317@dtor-ws> <20191205105206.slibwytrcteicx6y@pali> <20191206091114.kh255jrmerruumnq@pali> <20191206174048.GQ50317@dtor-ws> <20191218110224.44vcgdxh3j4bn7rw@pali> <20191218112659.crabhqkbcnxd6fo6@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20191218112659.crabhqkbcnxd6fo6@pali> User-Agent: NeoMutt/20180716 Sender: linux-bluetooth-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org On Wednesday 18 December 2019 12:26:59 Pali Rohár wrote: > On Wednesday 18 December 2019 12:02:24 Pali Rohár wrote: > > On Friday 06 December 2019 09:40:48 Dmitry Torokhov wrote: > > > On Fri, Dec 06, 2019 at 10:11:14AM +0100, Pali Rohár wrote: > > > > On Thursday 05 December 2019 12:03:05 Abhishek Pandit-Subedi wrote: > > > > > On Thu, Dec 5, 2019 at 2:52 AM Pali Rohár wrote: > > > > > > > > > > > > On Tuesday 03 December 2019 11:11:12 Dmitry Torokhov wrote: > > > > > > > On Tue, Dec 03, 2019 at 06:38:21PM +0100, Pali Rohár wrote: > > > > > > > > On Tuesday 03 December 2019 00:09:47 Pali Rohár wrote: > > > > > > > > > > > > > > > > Hi Dmitry! > > > > > > > > > > > > > > > > I was looking again at those _IOW defines for ioctl calls and I have > > > > > > > > another argument why not specify 'char *' in _IOW: > > > > > > > > > > > > > > > > All ioctls in _IOW() specify as a third macro argument type which is > > > > > > > > passed as pointer to the third argument for ioctl() syscall. > > > > > > > > > > > > > > > > So e.g.: > > > > > > > > > > > > > > > > #define EVIOCSCLOCKID _IOW('E', 0xa0, int) > > > > > > > > > > > > > > > > is called from userspace as: > > > > > > > > > > > > > > > > int val; > > > > > > > > ioctl(fd, EVIOCSCLOCKID, &val); > > > > > > > > > > > > > > > > Or > > > > > > > > > > > > > > > > #define EVIOCSMASK _IOW('E', 0x93, struct input_mask) > > > > > > > > > > > > > > > > is called as: > > > > > > > > > > > > > > > > struct input_mask val; > > > > > > > > ioctl(fd, EVIOCSMASK, &val); > > > > > > > > > > > > > > > > So basically third argument for _IOW specify size of byte buffer passed > > > > > > > > as third argument for ioctl(). In _IOW is not specified pointer to > > > > > > > > struct input_mask, but struct input_mask itself. > > > > > > > > > > > > > > > > And in case you define > > > > > > > > > > > > > > > > #define MY_NEW_IOCTL _IOW(UINPUT_IOCTL_BASE, 200, char*) > > > > > > > > > > > > > > > > then you by above usage you should pass data as: > > > > > > > > > > > > > > > > char *val = "DATA"; > > > > > > > > ioctl(fd, MY_NEW_IOCTL, &val); > > > > > > > > > > > > > > > > Which is not same as just: > > > > > > > > > > > > > > > > ioctl(fd, MY_NEW_IOCTL, "DATA"); > > > > > > > > > > > > > > > > As in former case you passed pointer to pointer to data and in later > > > > > > > > case you passed only pointer to data. > > > > > > > > > > > > > > > > It just mean that UI_SET_PHYS is already defined inconsistently which is > > > > > > > > also reason why compat ioctl for it was introduced. > > > > > > > > > > > > > > Yes, you are right. UI_SET_PHYS is messed up. I guess the question is > > > > > > > what to do with all of this... > > > > > > > > > > > > > > Maybe we should define > > > > > > > > > > > > > > #define UI_SET_PHYS_STR(len) _IOC(_IOC_WRITE, UINPUT_IOCTL_BASE, 111, len) > > > > > > > #define UI_SET_UNIQ_STR(len) _IOC(_IOC_WRITE, UINPUT_IOCTL_BASE, 112, len) > > > > > > > > > > > > I'm not sure if this is ideal. Normally in C strings are nul-termined, > > > > > > so functions/macros do not take buffer length. > > > > > Except strncpy, strndup, snprintf, etc. all expect a buffer length. At > > > > > > > > This is something different as for these functions you pass buffer and > > > > length of buffer which is used in write mode -- not for read mode. > > > > > > > > > the user to kernel boundary of ioctl, I think we should require size > > > > > of the user buffer regardless of the data type. > > > > > > > > > > > _STR therefore in names looks inconsistent. > > > > > The _STR suffix is odd (what to name UI_SET_PHYS_STR then??) but > > > > > requiring the length seems to be common across various ioctls. > > > > > * input.h requires a length when requesting the phys and uniq > > > > > (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/input.h#n138) > > > > > * Same with HIDRAW when setting and getting features: > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/hidraw.h#n40, > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/hidraw/hid-example.c#n88 > > > > > > > > All these ioctls where is passed length are in opposite direction > > > > (_IOC_READ) as our PHYS and UNIQ (_IOC_WRITE). > > > > > > > > I fully agree that when you need to read something from kernel > > > > (_IOC_READ) and then writing it to userspace, you need to specify length > > > > of userspace buffer. Exactly same as with userspace functions like > > > > memcpy, snprintf, etc... as you pointed. Otherwise you get buffer > > > > overflow as callee does not know length of buffer. > > > > > > > > But here we we have there quite different problem, we need to write > > > > something to kernel from userspace (_IOC_WRITE) and we are passing > > > > nul-term string. So in this case specifying size is not required as it > > > > is implicitly specified as part of passed string. > > > > > > With the new IOCTL definitions it does not need to be a NULL-terminated > > > string. It can be a buffer of characters with given length, and kernel > > > will NULL-terminate as this it what it wants, not what the caller has to > > > give. > > > > Hi Dmitry! I was thinking more about this problem and I will propose > > alternative solution, but first with details... > > > > I think that we should use NULL terminated strings. Or better disallow > > NULL byte inside string. Reason: all userspace application expects that > > input device name would be NULL terminated which implies that in the > > middle of name cannot be NULL byte. > > > > So this must apply also for new PHYS / UNIQ ioctl API. If we want in our > > ioctl API to use buffer + size (with upper bound limit for size) instead > > of passing NULL term string (with upper bound limit for string size) > > then kernel have to add a leading NULL byte to string, plus check that > > in the buffer there is no NULL byte. I guess this a very little > > complicate code, but nothing which is problematic. > > > > And on the userspace part. Now when userspace want to pass constant > > string for device name, it just call > > > > ioctl(fd, UI_SET_PHYS, "my name of device"); > > > > After adding a new ioctl with buffer + size API, userspace would have to > > call: > > > > ioctl(fd, UI_SET_PHYS_STR(strlen("my name of device")), "my name of device"); > > > > which looks strange, so programmers would had to move device name into > > new variable: > > > > const char *name = "my name of device"; > > ioctl(fd, UI_SET_PHYS_STR(strlen(name)), name); > > > > For me the old ioctl API looks easier to use (no need for strlen() or > > extra variable), but this is just my preference of usage -- as it is > > simpler for me. Maybe you would have different opinion... > > > > And now question: Why we have uinput_compat_ioctl()? It is there only > > because size part of IOCTL number is different on 32bit and 64bit > > systems. As we know size part of UI_SET_PHYS is wrong and does not make > > sense... > > > > Would not it be better to change size of UI_SET_PHYS to just zero and > > then when matching ioctl number just ignore size for this UI_SET_PHYS > > ioctl? Same for UI_BEGIN_FF_UPLOAD_COMPAT and UI_END_FF_UPLOAD_COMPAT > > added in: https://git.kernel.org/tip/tip/c/7c7da40 > > > > And we would not have to deal with uinput_compat_ioctl() at all. > > Below is example how change for removing UI_SET_PHYS_COMPAT may look > like. As header file is not changed and UI_SET_PHYS accepts any size > argument, it therefore accept also 32bit and 64bit integer. So no > existing 32bit applications which use UI_SET_PHYS on 64bit kernel would > not be broken... > > Is not this better change then introducing a new UI_SET_PHYS_STR ioctl > number? Because introduction of new IOCTL number has one big > disadvantage: Userspace applications needs to support fallback to old > number as older versions of kernels would be in use for a long time. And > because kernel does not have to remove old IOCTL number for backward > compatibility there is basically no need for userspace application to > user new UI_SET_PHYS_STR IOCTL number... Hello! I would like to remind this discussion as problem around a new UI_SET_UNIQ ioctl is not solved yet and uniq property is really useful for e.g. bluetooth (uinput) devices. Dmitry, when you have a time, could you please look at this discussion and decide how to go ahead? > diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c > index fd253781b..b645210d5 100644 > --- a/drivers/input/misc/uinput.c > +++ b/drivers/input/misc/uinput.c > @@ -915,22 +915,6 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd, > retval = uinput_set_bit(arg, propbit, INPUT_PROP_MAX); > goto out; > > - case UI_SET_PHYS: > - if (udev->state == UIST_CREATED) { > - retval = -EINVAL; > - goto out; > - } > - > - phys = strndup_user(p, 1024); > - if (IS_ERR(phys)) { > - retval = PTR_ERR(phys); > - goto out; > - } > - > - kfree(udev->dev->phys); > - udev->dev->phys = phys; > - goto out; > - > case UI_BEGIN_FF_UPLOAD: > retval = uinput_ff_upload_from_user(p, &ff_up); > if (retval) > @@ -1023,6 +1007,22 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd, > case UI_ABS_SETUP & ~IOCSIZE_MASK: > retval = uinput_abs_setup(udev, p, size); > goto out; > + > + case UI_SET_PHYS & ~IOCSIZE_MASK: > + if (udev->state == UIST_CREATED) { > + retval = -EINVAL; > + goto out; > + } > + > + phys = strndup_user(p, 1024); > + if (IS_ERR(phys)) { > + retval = PTR_ERR(phys); > + goto out; > + } > + > + kfree(udev->dev->phys); > + udev->dev->phys = phys; > + goto out; > } > > retval = -EINVAL; > @@ -1042,8 +1042,6 @@ static long uinput_ioctl(struct file *file, unsigned int cmd, unsigned long arg) > * These IOCTLs change their size and thus their numbers between > * 32 and 64 bits. > */ > -#define UI_SET_PHYS_COMPAT \ > - _IOW(UINPUT_IOCTL_BASE, 108, compat_uptr_t) > #define UI_BEGIN_FF_UPLOAD_COMPAT \ > _IOWR(UINPUT_IOCTL_BASE, 200, struct uinput_ff_upload_compat) > #define UI_END_FF_UPLOAD_COMPAT \ > @@ -1053,9 +1051,6 @@ static long uinput_compat_ioctl(struct file *file, > unsigned int cmd, unsigned long arg) > { > switch (cmd) { > - case UI_SET_PHYS_COMPAT: > - cmd = UI_SET_PHYS; > - break; > case UI_BEGIN_FF_UPLOAD_COMPAT: > cmd = UI_BEGIN_FF_UPLOAD; > break; > diff --git a/include/uapi/linux/uinput.h b/include/uapi/linux/uinput.h > index c9e677e3a..6bda2a142 100644 > --- a/include/uapi/linux/uinput.h > +++ b/include/uapi/linux/uinput.h > @@ -142,6 +142,8 @@ struct uinput_abs_setup { > #define UI_SET_LEDBIT _IOW(UINPUT_IOCTL_BASE, 105, int) > #define UI_SET_SNDBIT _IOW(UINPUT_IOCTL_BASE, 106, int) > #define UI_SET_FFBIT _IOW(UINPUT_IOCTL_BASE, 107, int) > +/* Argument is nul-term string and for backward compatibility is there > + * specified char*, but size argument (char *) is ignored by this ioctl */ > #define UI_SET_PHYS _IOW(UINPUT_IOCTL_BASE, 108, char*) > #define UI_SET_SWBIT _IOW(UINPUT_IOCTL_BASE, 109, int) > #define UI_SET_PROPBIT _IOW(UINPUT_IOCTL_BASE, 110, int) > > -- Pali Rohár pali.rohar@gmail.com