From: Arnd Bergmann <arnd@arndb.de> To: musl@lists.openwall.com Cc: Rich Felker <dalias@libc.org>, Arnd Bergmann <arnd@arndb.de>, Michael Forney <mforney@mforney.org>, ALSA Development Mailing List <alsa-devel@alsa-project.org>, Takashi Iwai <tiwai@suse.com>, Baolin Wang <baolin.wang@linaro.org>, y2038 Mailman List <y2038@lists.linaro.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Mark Brown <broonie@kernel.org>, Baolin Wang <baolin.wang7@gmail.com> Subject: Re: [musl] Re: [alsa-devel] [PATCH v7 8/9] ALSA: add new 32-bit layout for snd_pcm_mmap_status/control Date: Fri, 8 Oct 2021 11:24:39 +0200 [thread overview] Message-ID: <CAK8P3a0qxNLv3_RcR5COcRGPcTnYMcfbOjdWKiT2hKdcof9WUg@mail.gmail.com> (raw) In-Reply-To: <s5h5yu79aab.wl-tiwai@suse.de> On Fri, Oct 8, 2021 at 10:43 AM Takashi Iwai <tiwai@suse.de> wrote: > On Thu, 07 Oct 2021 18:51:58 +0200, Rich Felker wrote: > > On Thu, Oct 07, 2021 at 06:18:52PM +0200, Takashi Iwai wrote: > > @@ -557,11 +558,15 @@ struct __snd_pcm_sync_ptr { > #if defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : defined(__BIG_ENDIAN) > typedef char __pad_before_uframe[sizeof(__u64) - sizeof(snd_pcm_uframes_t)]; > typedef char __pad_after_uframe[0]; > +typedef char __pad_before_u32[4]; > +typedef char __pad_after_u32[0]; > #endif > > #if defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : defined(__LITTLE_ENDIAN) > typedef char __pad_before_uframe[0]; > typedef char __pad_after_uframe[sizeof(__u64) - sizeof(snd_pcm_uframes_t)]; > +typedef char __pad_before_u32[0]; > +typedef char __pad_after_u32[4]; > #endif I think these should remain unchanged, the complex expression was intentionally done so the structures are laid out the same way on 64-bit architectures, so that the kernel can use the __SND_STRUCT_TIME64 path internally on both 32-bit and 64-bit architectures. > @@ -2970,8 +2981,17 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream, > memset(&sync_ptr, 0, sizeof(sync_ptr)); > if (get_user(sync_ptr.flags, (unsigned __user *)&(_sync_ptr->flags))) > return -EFAULT; > - if (copy_from_user(&sync_ptr.c.control, &(_sync_ptr->c.control), sizeof(struct snd_pcm_mmap_control))) > - return -EFAULT; > + if (buggy_control) { > + if (copy_from_user(&sync_ptr.c.control_api_2_0_15, > + &(_sync_ptr->c.control_api_2_0_15), > + sizeof(sync_ptr.c.control_api_2_0_15))) > + return -EFAULT; > + } else { > + if (copy_from_user(&sync_ptr.c.control, > + &(_sync_ptr->c.control), > + sizeof(sync_ptr.c.control))) > + return -EFAULT; > + } The problem I see with this is that it might break musl's ability to emulate the new interface on top of the old (time32) one for linux-4.x and older kernels, as the conversion function is no longer stateless but has to know the negotiated interface version. It's probably fine as long as we can be sure that the 2.0.16+ API version only gets negotiated if both the kernel and user sides support it, and musl only emulates the 2.0.15 API version from the current kernels. I've tried to understand this part of musl's convert_ioctl_struct(), but I just can't figure out whether it does the conversion based the on the layout that is currently used in the kernel, or based on the layout we should have been using, and would use with the above fix. Rich, can you help me here? Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de> To: musl@lists.openwall.com Cc: ALSA Development Mailing List <alsa-devel@alsa-project.org>, Rich Felker <dalias@libc.org>, Arnd Bergmann <arnd@arndb.de>, Baolin Wang <baolin.wang@linaro.org>, y2038 Mailman List <y2038@lists.linaro.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Takashi Iwai <tiwai@suse.com>, Michael Forney <mforney@mforney.org>, Mark Brown <broonie@kernel.org>, Baolin Wang <baolin.wang7@gmail.com> Subject: Re: [musl] Re: [alsa-devel] [PATCH v7 8/9] ALSA: add new 32-bit layout for snd_pcm_mmap_status/control Date: Fri, 8 Oct 2021 11:24:39 +0200 [thread overview] Message-ID: <CAK8P3a0qxNLv3_RcR5COcRGPcTnYMcfbOjdWKiT2hKdcof9WUg@mail.gmail.com> (raw) In-Reply-To: <s5h5yu79aab.wl-tiwai@suse.de> On Fri, Oct 8, 2021 at 10:43 AM Takashi Iwai <tiwai@suse.de> wrote: > On Thu, 07 Oct 2021 18:51:58 +0200, Rich Felker wrote: > > On Thu, Oct 07, 2021 at 06:18:52PM +0200, Takashi Iwai wrote: > > @@ -557,11 +558,15 @@ struct __snd_pcm_sync_ptr { > #if defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : defined(__BIG_ENDIAN) > typedef char __pad_before_uframe[sizeof(__u64) - sizeof(snd_pcm_uframes_t)]; > typedef char __pad_after_uframe[0]; > +typedef char __pad_before_u32[4]; > +typedef char __pad_after_u32[0]; > #endif > > #if defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : defined(__LITTLE_ENDIAN) > typedef char __pad_before_uframe[0]; > typedef char __pad_after_uframe[sizeof(__u64) - sizeof(snd_pcm_uframes_t)]; > +typedef char __pad_before_u32[0]; > +typedef char __pad_after_u32[4]; > #endif I think these should remain unchanged, the complex expression was intentionally done so the structures are laid out the same way on 64-bit architectures, so that the kernel can use the __SND_STRUCT_TIME64 path internally on both 32-bit and 64-bit architectures. > @@ -2970,8 +2981,17 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream, > memset(&sync_ptr, 0, sizeof(sync_ptr)); > if (get_user(sync_ptr.flags, (unsigned __user *)&(_sync_ptr->flags))) > return -EFAULT; > - if (copy_from_user(&sync_ptr.c.control, &(_sync_ptr->c.control), sizeof(struct snd_pcm_mmap_control))) > - return -EFAULT; > + if (buggy_control) { > + if (copy_from_user(&sync_ptr.c.control_api_2_0_15, > + &(_sync_ptr->c.control_api_2_0_15), > + sizeof(sync_ptr.c.control_api_2_0_15))) > + return -EFAULT; > + } else { > + if (copy_from_user(&sync_ptr.c.control, > + &(_sync_ptr->c.control), > + sizeof(sync_ptr.c.control))) > + return -EFAULT; > + } The problem I see with this is that it might break musl's ability to emulate the new interface on top of the old (time32) one for linux-4.x and older kernels, as the conversion function is no longer stateless but has to know the negotiated interface version. It's probably fine as long as we can be sure that the 2.0.16+ API version only gets negotiated if both the kernel and user sides support it, and musl only emulates the 2.0.15 API version from the current kernels. I've tried to understand this part of musl's convert_ioctl_struct(), but I just can't figure out whether it does the conversion based the on the layout that is currently used in the kernel, or based on the layout we should have been using, and would use with the above fix. Rich, can you help me here? Arnd
next prev parent reply other threads:[~2021-10-08 9:25 UTC|newest] Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-11 21:20 [PATCH v7 0/8] Fix year 2038 issue for sound subsystem Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 1/9] ALSA: Replace timespec with timespec64 Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 2/9] ALSA: Avoid using timespec for struct snd_timer_status Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 3/9] ALSA: Avoid using timespec for struct snd_ctl_elem_value Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 4/9] ALSA: Avoid using timespec for struct snd_pcm_status Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 5/9] ALSA: Avoid using timespec for struct snd_rawmidi_status Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 6/9] ALSA: Avoid using timespec for struct snd_timer_tread Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-12 0:14 ` [Y2038] " Ben Hutchings 2019-12-12 0:14 ` [alsa-devel] " Ben Hutchings 2019-12-12 9:57 ` Arnd Bergmann 2019-12-12 9:57 ` [alsa-devel] " Arnd Bergmann 2019-12-12 14:27 ` Ben Hutchings 2019-12-12 14:27 ` [alsa-devel] " Ben Hutchings 2019-12-13 10:25 ` Arnd Bergmann 2019-12-13 10:25 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 7/9] ALSA: move snd_pcm_ioctl_sync_ptr_compat into pcm_native.c Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-11 21:20 ` [PATCH v7 8/9] ALSA: add new 32-bit layout for snd_pcm_mmap_status/control Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2021-10-06 17:49 ` Michael Forney 2021-10-06 17:49 ` Michael Forney 2021-10-07 10:52 ` Takashi Iwai 2021-10-07 10:52 ` Takashi Iwai 2021-10-07 11:48 ` Arnd Bergmann 2021-10-07 11:48 ` Arnd Bergmann 2021-10-07 12:43 ` Takashi Iwai 2021-10-07 12:43 ` Takashi Iwai 2021-10-07 13:02 ` Takashi Iwai 2021-10-07 13:02 ` Takashi Iwai 2021-10-07 13:11 ` Arnd Bergmann 2021-10-07 13:11 ` Arnd Bergmann 2021-10-07 15:33 ` Takashi Iwai 2021-10-07 15:33 ` Takashi Iwai 2021-10-07 16:06 ` [musl] " Rich Felker 2021-10-07 16:06 ` Rich Felker 2021-10-07 16:18 ` Takashi Iwai 2021-10-07 16:18 ` Takashi Iwai 2021-10-07 16:51 ` Rich Felker 2021-10-07 16:51 ` Rich Felker 2021-10-08 8:43 ` Takashi Iwai 2021-10-08 8:43 ` Takashi Iwai 2021-10-08 8:44 ` Takashi Iwai 2021-10-08 8:44 ` Takashi Iwai 2021-10-08 9:24 ` Arnd Bergmann [this message] 2021-10-08 9:24 ` Arnd Bergmann 2021-10-08 11:11 ` Takashi Iwai 2021-10-08 11:11 ` Takashi Iwai 2021-10-08 11:45 ` Arnd Bergmann 2021-10-08 11:45 ` Arnd Bergmann 2021-10-08 11:53 ` Takashi Iwai 2021-10-08 11:53 ` Takashi Iwai 2021-10-08 12:13 ` Arnd Bergmann 2021-10-08 12:13 ` Arnd Bergmann 2021-10-08 12:07 ` Rich Felker 2021-10-08 12:07 ` Rich Felker 2021-10-10 7:53 ` Takashi Iwai 2021-10-10 7:53 ` Takashi Iwai 2021-10-18 14:43 ` Rich Felker 2021-10-18 14:43 ` Rich Felker 2021-10-18 14:58 ` Takashi Iwai 2021-10-18 14:58 ` Takashi Iwai 2021-10-18 15:08 ` Rich Felker 2021-10-18 15:08 ` Rich Felker 2021-10-18 15:26 ` Arnd Bergmann 2021-10-18 15:26 ` Arnd Bergmann 2021-10-18 20:42 ` Rich Felker 2021-10-18 20:42 ` Rich Felker 2021-10-19 14:16 ` Rich Felker 2021-10-19 14:16 ` Rich Felker 2021-10-19 14:23 ` Arnd Bergmann 2021-10-19 14:23 ` Arnd Bergmann 2021-10-08 12:06 ` Rich Felker 2021-10-08 12:06 ` Rich Felker 2021-10-08 12:37 ` Arnd Bergmann 2021-10-08 12:37 ` Arnd Bergmann 2021-10-08 17:20 ` Rich Felker 2021-10-08 17:20 ` Rich Felker 2019-12-11 21:20 ` [PATCH v7 9/9] ALSA: bump uapi version numbers Arnd Bergmann 2019-12-11 21:20 ` [alsa-devel] " Arnd Bergmann 2019-12-17 10:42 ` [PATCH v7 0/8] Fix year 2038 issue for sound subsystem Takashi Iwai 2019-12-17 10:42 ` [alsa-devel] " Takashi Iwai 2019-12-17 21:15 ` Arnd Bergmann 2019-12-17 21:15 ` [alsa-devel] " Arnd Bergmann 2019-12-17 21:16 ` [GIT PULL, v8] " Arnd Bergmann 2019-12-17 21:16 ` [alsa-devel] " Arnd Bergmann 2019-12-17 22:22 ` [PATCH v7 0/8] " Takashi Iwai 2019-12-17 22:22 ` [alsa-devel] " Takashi Iwai
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