From: Peter Collingbourne <[email protected]>
[ This issue was fixed upstream by accident in c3cee924bd85 ("arm64:
head: cover entire kernel image in initial ID map") as part of a
large refactoring of the arm64 boot flow. This simple fix is therefore
preferred for -stable backporting ]
On a system that implements FEAT_EPAN, read/write access to the idmap
is denied because UXN is not set on the swapper PTEs. As a result,
idmap_kpti_install_ng_mappings panics the kernel when accessing
__idmap_kpti_flag. Fix it by setting UXN on these PTEs.
Fixes: 18107f8a2df6 ("arm64: Support execute-only permissions with Enhanced PAN")
Cc: <[email protected]> # 5.15
Link: https://linux-review.googlesource.com/id/Ic452fa4b4f74753e54f71e61027e7222a0fae1b1
Signed-off-by: Peter Collingbourne <[email protected]>
Acked-by: Will Deacon <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Catalin Marinas <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>
---
arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
arch/arm64/kernel/head.S | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 96dc0f7da258..a971d462f531 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -103,8 +103,8 @@
/*
* Initial memory map attributes.
*/
-#define SWAPPER_PTE_FLAGS (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
-#define SWAPPER_PMD_FLAGS (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
+#define SWAPPER_PTE_FLAGS (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED | PTE_UXN)
+#define SWAPPER_PMD_FLAGS (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S | PMD_SECT_UXN)
#if ARM64_KERNEL_USES_PMD_MAPS
#define SWAPPER_MM_MMUFLAGS (PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6a98f1a38c29..8a93a0a7489b 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -285,7 +285,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
subs x1, x1, #64
b.ne 1b
- mov x7, SWAPPER_MM_MMUFLAGS
+ mov_q x7, SWAPPER_MM_MMUFLAGS
/*
* Create the identity mapping.
--
2.37.1.559.g78731f0fdb-goog
On Mon, Aug 08, 2022 at 01:53:21PM +0100, Will Deacon wrote:
> From: Peter Collingbourne <[email protected]>
>
> [ This issue was fixed upstream by accident in c3cee924bd85 ("arm64:
> head: cover entire kernel image in initial ID map") as part of a
> large refactoring of the arm64 boot flow. This simple fix is therefore
> preferred for -stable backporting ]
>
> On a system that implements FEAT_EPAN, read/write access to the idmap
> is denied because UXN is not set on the swapper PTEs. As a result,
> idmap_kpti_install_ng_mappings panics the kernel when accessing
> __idmap_kpti_flag. Fix it by setting UXN on these PTEs.
>
> Fixes: 18107f8a2df6 ("arm64: Support execute-only permissions with Enhanced PAN")
> Cc: <[email protected]> # 5.15
> Link: https://linux-review.googlesource.com/id/Ic452fa4b4f74753e54f71e61027e7222a0fae1b1
> Signed-off-by: Peter Collingbourne <[email protected]>
> Acked-by: Will Deacon <[email protected]>
> Cc: Ard Biesheuvel <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Link: https://lore.kernel.org/r/[email protected]
> Signed-off-by: Will Deacon <[email protected]>
> ---
> arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
> arch/arm64/kernel/head.S | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
So this should be added to 5.15.y, 5.18.y, and 5.19.y? Or some subset?
thanks,
greg k-h
On Mon, Aug 08, 2022 at 03:23:55PM +0200, Greg KH wrote:
> On Mon, Aug 08, 2022 at 01:53:21PM +0100, Will Deacon wrote:
> > From: Peter Collingbourne <[email protected]>
> >
> > [ This issue was fixed upstream by accident in c3cee924bd85 ("arm64:
> > head: cover entire kernel image in initial ID map") as part of a
> > large refactoring of the arm64 boot flow. This simple fix is therefore
> > preferred for -stable backporting ]
> >
> > On a system that implements FEAT_EPAN, read/write access to the idmap
> > is denied because UXN is not set on the swapper PTEs. As a result,
> > idmap_kpti_install_ng_mappings panics the kernel when accessing
> > __idmap_kpti_flag. Fix it by setting UXN on these PTEs.
> >
> > Fixes: 18107f8a2df6 ("arm64: Support execute-only permissions with Enhanced PAN")
> > Cc: <[email protected]> # 5.15
> > Link: https://linux-review.googlesource.com/id/Ic452fa4b4f74753e54f71e61027e7222a0fae1b1
> > Signed-off-by: Peter Collingbourne <[email protected]>
> > Acked-by: Will Deacon <[email protected]>
> > Cc: Ard Biesheuvel <[email protected]>
> > Cc: Catalin Marinas <[email protected]>
> > Link: https://lore.kernel.org/r/[email protected]
> > Signed-off-by: Will Deacon <[email protected]>
> > ---
> > arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
> > arch/arm64/kernel/head.S | 2 +-
> > 2 files changed, 3 insertions(+), 3 deletions(-)
>
> So this should be added to 5.15.y, 5.18.y, and 5.19.y? Or some subset?
Yes, all of them. Basically anything still being updated which is >= 5.15
and <= 5.19.
Thanks,
Will