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ARM: 8722/1: mm: make STRICT_KERNEL_RWX effective for LPAE

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Currently, for ARM kernels with CONFIG_ARM_LPAE and
CONFIG_STRICT_KERNEL_RWX enabled, the 2MiB pages mapping the
kernel code and rodata are writable. They are marked read-only in
a software bit (L_PMD_SECT_RDONLY) but the hardware read-only bit
is not set (PMD_SECT_AP2).

For user mappings, the logic that propagates the software bit
to the hardware bit is in set_pmd_at(); but for the kernel,
section_update() writes the PMDs directly, skipping this logic.

The fix is to set PMD_SECT_AP2 for read-only sections in
section_update(), at the same time as L_PMD_SECT_RDONLY.

Fixes: 1e3479225a ("ARM: 8275/1: mm: fix PMD_SECT_RDONLY undeclared compile error")
Signed-off-by: Philip Derrin <philip@cog.systems>
Reported-by: Neil Dick <neil@cog.systems>
Tested-by: Neil Dick <neil@cog.systems>
Tested-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Philip Derrin 2017-11-14 00:55:25 +01:00 committed by Russell King
parent 3b0c0c922f
commit 400eeffaff
1 changed files with 2 additions and 2 deletions
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4
arch/arm/mm/init.c
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@ -639,8 +639,8 @@ static struct section_perm ro_perms[] = {
.start = (unsigned long)_stext,
.end = (unsigned long)__init_begin,
#ifdef CONFIG_ARM_LPAE
.mask = ~L_PMD_SECT_RDONLY,
.prot = L_PMD_SECT_RDONLY,
.mask = ~(L_PMD_SECT_RDONLY | PMD_SECT_AP2),
.prot = L_PMD_SECT_RDONLY | PMD_SECT_AP2,
#else
.mask = ~(PMD_SECT_APX | PMD_SECT_AP_WRITE),
.prot = PMD_SECT_APX | PMD_SECT_AP_WRITE,