Messages in this thread | | | Date | Thu, 22 Aug 2019 01:55:34 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH] aio: Fix io_pgetevents() struct __compat_aio_sigset layout |
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On Wed, Aug 21, 2019 at 05:38:20AM +0200, Guillem Jover wrote: > This type is used to pass the sigset_t from userland to the kernel, > but it was using the kernel native pointer type for the member > representing the compat userland pointer to the userland sigset_t. > > This messes up the layout, and makes the kernel eat up both the > userland pointer and the size members into the kernel pointer, and > then reads garbage into the kernel sigsetsize. Which makes the sigset_t > size consistency check fail, and consequently the syscall always > returns -EINVAL. > > This breaks both libaio and strace on 32-bit userland running on 64-bit > kernels. And there are apparently no users in the wild of the current > broken layout (at least according to codesearch.debian.org and a brief > check over github.com search). So it looks safe to fix this directly > in the kernel, instead of either letting userland deal with this > permanently with the additional overhead or trying to make the syscall > infer what layout userland used, even though this is also being worked > around in libaio to temporarily cope with kernels that have not yet > been fixed. > > We use a proper compat_uptr_t instead of a compat_sigset_t pointer. > > Fixes: 7a074e96 ("aio: implement io_pgetevents") > Signed-off-by: Guillem Jover <guillem@hadrons.org>
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
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