Re: [PATCH] aio: Fix io_pgetevents() struct __compat_aio_sigset layout
On Thu, Oct 17, 2019 at 03:48:00PM +0200, Jan Kara wrote:
> On Wed 21-08-19 05:38:20, 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
>
> This patch seems to have fallen through the cracks. Al?
Looks like - back then I assumed that Jens would've picked it...
Applied to #fixes...
Re: [PATCH] aio: Fix io_pgetevents() struct __compat_aio_sigset layout
On Wed 21-08-19 05:38:20, 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
This patch seems to have fallen through the cracks. Al?
Honza
> ---
> fs/aio.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 01e0fb9ae45a..056f291bc66f 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -2179,7 +2179,7 @@ SYSCALL_DEFINE5(io_getevents_time32, __u32, ctx_id,
> #ifdef CONFIG_COMPAT
>
> struct __compat_aio_sigset {
> - compat_sigset_t __user *sigmask;
> + compat_uptr_t sigmask;
> compat_size_t sigsetsize;
> };
>
> @@ -2204,7 +2204,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
> if (usig && copy_from_user(, usig, sizeof(ksig)))
> return -EFAULT;
>
> - ret = set_compat_user_sigmask(ksig.sigmask, ksig.sigsetsize);
> + ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask),
> ksig.sigsetsize);
> if (ret)
> return ret;
>
> @@ -2239,7 +2239,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
> if (usig && copy_from_user(, usig, sizeof(ksig)))
> return -EFAULT;
>
> - ret = set_compat_user_sigmask(ksig.sigmask, ksig.sigsetsize);
> + ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask),
> ksig.sigsetsize);
> if (ret)
> return ret;
>
> --
> 2.23.0
>
--
Jan Kara
SUSE Labs, CR
Re: [PATCH] aio: Fix io_pgetevents() struct __compat_aio_sigset layout
Guillem Jover writes:
> 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
Looks good, thanks for finding and fixing this!
Reviewed-by: Jeff Moyer
> ---
> fs/aio.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 01e0fb9ae45a..056f291bc66f 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -2179,7 +2179,7 @@ SYSCALL_DEFINE5(io_getevents_time32, __u32, ctx_id,
> #ifdef CONFIG_COMPAT
>
> struct __compat_aio_sigset {
> - compat_sigset_t __user *sigmask;
> + compat_uptr_t sigmask;
> compat_size_t sigsetsize;
> };
>
> @@ -2204,7 +2204,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
> if (usig && copy_from_user(, usig, sizeof(ksig)))
> return -EFAULT;
>
> - ret = set_compat_user_sigmask(ksig.sigmask, ksig.sigsetsize);
> + ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask),
> ksig.sigsetsize);
> if (ret)
> return ret;
>
> @@ -2239,7 +2239,7 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
> if (usig && copy_from_user(, usig, sizeof(ksig)))
> return -EFAULT;
>
> - ret = set_compat_user_sigmask(ksig.sigmask, ksig.sigsetsize);
> + ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask),
> ksig.sigsetsize);
> if (ret)
> return ret;
Re: [PATCH] aio: Fix io_pgetevents() struct __compat_aio_sigset layout
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
Looks good,
Reviewed-by: Christoph Hellwig
