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Groups > linux.kernel > #1738754
| From | Ingo Molnar <mingo@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() |
| Date | 2017-09-25 08:20 +0200 |
| Message-ID | <utuUh-2ui-1@gated-at.bofh.it> (permalink) |
| References | <utcNH-7Gh-3@gated-at.bofh.it> <utcXo-7Yz-9@gated-at.bofh.it> <utkid-3NE-13@gated-at.bofh.it> <utkrU-46H-5@gated-at.bofh.it> <utlnZ-4Gy-33@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
* Eric Biggers <ebiggers3@gmail.com> wrote:
> On Sun, Sep 24, 2017 at 09:02:42PM +0200, Ingo Molnar wrote:
> >
> > * Eric Biggers <ebiggers3@gmail.com> wrote:
> >
> > > On Sun, Sep 24, 2017 at 12:59:06PM +0200, Ingo Molnar wrote:
> > > > @@ -328,10 +331,8 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
> > > > err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
> > > > } else {
> > > > err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
> > > > -
> > > > - /* xcomp_bv must be 0 when using uncompacted format */
> > > > - if (!err && fpu->state.xsave.header.xcomp_bv)
> > > > - err = -EINVAL;
> > > > + if (!err)
> > > > + err = validate_xstate_header(&fpu->state.xsave.header);
> > > > }
> > > >
> > >
> > > Sorry, this is the buggy part. The problem is that this code runs even if XSAVE
> > > isn't being used --- and in that case the state size is 512 bytes or less, so
> > > the state doesn't actually include the xstate_header. So
> > > validate_xstate_header() was reading out of bounds and seeing invalid values.
> > >
> > > So I think we need to check use_xsave() here, but it really needs to be in the
> > > earlier patch which added the check for just ->xcomp_bv ("x86/fpu: Don't let
> > > userspace set bogus xcomp_bv"), not in this one.
> > >
> > > As far the split of patch 2/3 into these 10 patches, it looks fine (though it
> > > suddenly became a *lot* of patches!). One nit: the subject of this one really
> > > should say "__fpu__restore_sig()", not "sanitize_restored_xstate()".
> > >
> > > I can send a fixed series when I have a chance.
> >
> > Could you please just send the delta patch against the whole tree to fix the bug?
> > I'll worry about the patch dependencies and back-merge it to the proper place.
> >
>
> The following diff against tip/master fixes the bug. Note: we *could* check
> 'use_xsave()' instead of 'state_size > offsetof(struct xregs_state, header)',
> but that might be confusing in the case where we couldn't find the xstate
> information in the memory layout and only copy the fxregs_state, since then we'd
> actually be validating the xsave_header which was already there, which shouldn't
> ever fail.
>
> diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
> index afe54247cf27..fb639e70048f 100644
> --- a/arch/x86/kernel/fpu/signal.c
> +++ b/arch/x86/kernel/fpu/signal.c
> @@ -331,7 +331,8 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
> err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
> } else {
> err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
> - if (!err)
> +
> + if (!err && state_size > offsetof(struct xregs_state, header))
> err = validate_xstate_header(&fpu->state.xsave.header);
> }
I.e. a better check would be to check that the whole header can be accessed:
state_size >= offsetof(struct xregs_state, header) + sizeof(struct xstate_header)
Not that there should ever be a 'state_size' that points inside the header - so in
the end I back-merged your original (and tested ...) version.
Thanks,
Ingo
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[PATCH 00/10] x86/fpu: Split up "x86/fpu: Tighten validation of user-supplied xstate_header" Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:00 +0200
[PATCH 02/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in xstateregs_set() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:00 +0200
[tip:x86/fpu] x86/fpu: Use validate_xstate_header() to validate the xstate_header in xstateregs_set() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 09/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_user_to_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:00 +0200
[tip:x86/fpu] x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_user_to_xstate() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 10/10] x86/fpu: Use using_compacted_format() instead of open coded X86_FEATURE_XSAVES Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:10 +0200
[tip:x86/fpu] x86/fpu: Use using_compacted_format() instead of open coded X86_FEATURE_XSAVES tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:10 +0200
Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Eric Biggers <ebiggers3@gmail.com> - 2017-09-24 21:00 +0200
Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-24 21:10 +0200
Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Eric Biggers <ebiggers3@gmail.com> - 2017-09-24 22:10 +0200
Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-25 08:10 +0200
Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-25 08:20 +0200
Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Eric Biggers <ebiggers3@gmail.com> - 2017-09-25 09:30 +0200
Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-25 09:40 +0200
[tip:x86/fpu] x86/fpu: Use validate_xstate_header() to validate the xstate_header in __fpu__restore_sig() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 07/10] x86/fpu: Copy the full header in copy_user_to_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:10 +0200
[tip:x86/fpu] x86/fpu: Copy the full header in copy_user_to_xstate() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 01/10] x86/fpu: Introduce validate_xstate_header() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:10 +0200
[tip:x86/fpu] x86/fpu: Introduce validate_xstate_header() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 08/10] x86/fpu: Eliminate the 'xfeatures' local variable in copy_user_to_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:10 +0200
[tip:x86/fpu] x86/fpu: Eliminate the 'xfeatures' local variable in copy_user_to_xstate() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 04/10] x86/fpu: Copy the full state_header in copy_kernel_to_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:10 +0200
[tip:x86/fpu] x86/fpu: Copy the full state_header in copy_kernel_to_xstate() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 06/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_kernel_to_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-24 13:10 +0200
[tip:x86/fpu] x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_kernel_to_xstate() tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
Re: [PATCH 00/10] x86/fpu: Split up "x86/fpu: Tighten validation of user-supplied xstate_header" Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-24 20:10 +0200
Re: [PATCH 00/10] x86/fpu: Split up "x86/fpu: Tighten validation of user-supplied xstate_header" Ingo Molnar <mingo@kernel.org> - 2017-09-24 21:10 +0200
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