On Fri, Oct 08, 2021 at 01:11:34PM +0200, Takashi Iwai wrote: > On Fri, 08 Oct 2021 11:24:39 +0200, > Arnd Bergmann wrote: > > > > On Fri, Oct 8, 2021 at 10:43 AM Takashi Iwai <ti...@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. > > That was explicitly defined, but OK, this isn't necessarily defined > here. > > > > @@ -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? > > So, at this moment, I'm not sure whether we should correct the struct > at all. This will lead to yet more breakage, and basically the struct > itself *works* -- the only bug is in 32bit compat handling in the > kernel (again). > > The below is a revised kernel patch (again untested), just correcting > the behavior of 32bit compat mode. 32bit apps on 32bit kernel work > fine as is, as well as 64bit apps on 64bit kernel.
I'm perfectly okay with this if Arnd is! It's probably the least invasive and has the least long-term maintenance cost and fallout on other projects. Rich _______________________________________________ Y2038 mailing list Y2038@lists.linaro.org https://lists.linaro.org/mailman/listinfo/y2038