| Message ID | 20191016105303.21948-1-julien.grall@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [Xen-devel,for-4.13,v2] xen/arm: Don't use _end in is_xen_fixed_mfn() | expand |
On Wed, 16 Oct 2019, Julien Grall wrote: > virt_to_maddr() is using the hardware page-table walk instructions to > translate a virtual address to physical address. The function should > only be called on virtual address mapped. > > _end points past the end of Xen binary and may not be mapped when the > binary size is page-aligned. This means virt_to_maddr() will not be able > to do the translation and therefore crash Xen. > > Note there is also an off-by-one issue in this code, but the panic will > trump that. > > Both issues can be fixed by using _end - 1 in the check. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > Release-acked-by: Juergen Gross <jgross@suse.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > > Cc: Andrew Cooper <andrew.cooper3@citrix.com> > Cc: George Dunlap <George.Dunlap@eu.citrix.com> > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > Cc: Jan Beulich <jbeulich@suse.com> > Cc: Julien Grall <julien@xen.org> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Cc: Stefano Stabellini <sstabellini@kernel.org> > Cc: Tim Deegan <tim@xen.org> > Cc: Wei Liu <wl@xen.org> > > x86 seems to be affected by the off-by-one issue. Jan, Andrew? > > This could be reached by a domain via XEN_SYSCTL_page_offline_op. > However, the operation is not security supported (see XSA-77). So we are > fine here. > > Changes in v2: > - Cast _end to vaddr_t to prevent UB. > - Add Juergen's released-acked-by > --- > xen/include/asm-arm/mm.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h > index 262d92f18d..333efd3a60 100644 > --- a/xen/include/asm-arm/mm.h > +++ b/xen/include/asm-arm/mm.h > @@ -153,7 +153,7 @@ extern unsigned long xenheap_base_pdx; > > #define is_xen_fixed_mfn(mfn) \ > ((mfn_to_maddr(mfn) >= virt_to_maddr(&_start)) && \ > - (mfn_to_maddr(mfn) <= virt_to_maddr(&_end))) > + (mfn_to_maddr(mfn) <= virt_to_maddr((vaddr_t)_end - 1))) > > #define page_get_owner(_p) (_p)->v.inuse.domain > #define page_set_owner(_p,_d) ((_p)->v.inuse.domain = (_d)) > -- > 2.11.0 >
On 16.10.2019 12:53, Julien Grall wrote: > virt_to_maddr() is using the hardware page-table walk instructions to > translate a virtual address to physical address. The function should > only be called on virtual address mapped. > > _end points past the end of Xen binary and may not be mapped when the > binary size is page-aligned. This means virt_to_maddr() will not be able > to do the translation and therefore crash Xen. > > Note there is also an off-by-one issue in this code, but the panic will > trump that. > > Both issues can be fixed by using _end - 1 in the check. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > Release-acked-by: Juergen Gross <jgross@suse.com> > > --- > > Cc: Andrew Cooper <andrew.cooper3@citrix.com> > Cc: George Dunlap <George.Dunlap@eu.citrix.com> > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > Cc: Jan Beulich <jbeulich@suse.com> > Cc: Julien Grall <julien@xen.org> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Cc: Stefano Stabellini <sstabellini@kernel.org> > Cc: Tim Deegan <tim@xen.org> > Cc: Wei Liu <wl@xen.org> > > x86 seems to be affected by the off-by-one issue. Jan, Andrew? Indeed. I'm in the process of making a patch. Jan
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h index 262d92f18d..333efd3a60 100644 --- a/xen/include/asm-arm/mm.h +++ b/xen/include/asm-arm/mm.h @@ -153,7 +153,7 @@ extern unsigned long xenheap_base_pdx; #define is_xen_fixed_mfn(mfn) \ ((mfn_to_maddr(mfn) >= virt_to_maddr(&_start)) && \ - (mfn_to_maddr(mfn) <= virt_to_maddr(&_end))) + (mfn_to_maddr(mfn) <= virt_to_maddr((vaddr_t)_end - 1))) #define page_get_owner(_p) (_p)->v.inuse.domain #define page_set_owner(_p,_d) ((_p)->v.inuse.domain = (_d))
virt_to_maddr() is using the hardware page-table walk instructions to translate a virtual address to physical address. The function should only be called on virtual address mapped. _end points past the end of Xen binary and may not be mapped when the binary size is page-aligned. This means virt_to_maddr() will not be able to do the translation and therefore crash Xen. Note there is also an off-by-one issue in this code, but the panic will trump that. Both issues can be fixed by using _end - 1 in the check. Signed-off-by: Julien Grall <julien.grall@arm.com> Release-acked-by: Juergen Gross <jgross@suse.com> --- Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: George Dunlap <George.Dunlap@eu.citrix.com> Cc: Ian Jackson <ian.jackson@eu.citrix.com> Cc: Jan Beulich <jbeulich@suse.com> Cc: Julien Grall <julien@xen.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Tim Deegan <tim@xen.org> Cc: Wei Liu <wl@xen.org> x86 seems to be affected by the off-by-one issue. Jan, Andrew? This could be reached by a domain via XEN_SYSCTL_page_offline_op. However, the operation is not security supported (see XSA-77). So we are fine here. Changes in v2: - Cast _end to vaddr_t to prevent UB. - Add Juergen's released-acked-by --- xen/include/asm-arm/mm.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)