3.16.54-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Philip Derrin <philip@cog.systems> commit 3b0c0c922ff4be275a8beb87ce5657d16f355b54 upstream. When CONFIG_ARM_LPAE is set, the PMD dump relies on the software read-only bit to determine whether a page is writable. This concealed a bug which left the kernel text section writable (AP2=0) while marked read-only in the software bit. In a kernel with the AP2 bug, the dump looks like this: ---[ Kernel Mapping ]--- 0xc0000000-0xc0200000 2M RW NX SHD 0xc0200000-0xc0600000 4M ro x SHD 0xc0600000-0xc0800000 2M ro NX SHD 0xc0800000-0xc4800000 64M RW NX SHD The fix is to check that the software and hardware bits are both set before displaying "ro". The dump then shows the true perms: ---[ Kernel Mapping ]--- 0xc0000000-0xc0200000 2M RW NX SHD 0xc0200000-0xc0600000 4M RW x SHD 0xc0600000-0xc0800000 2M RW NX SHD 0xc0800000-0xc4800000 64M RW NX SHD Fixes: ded947798469 ("ARM: 8109/1: mm: Modify pte_write and pmd_write logic for LPAE") Signed-off-by: Philip Derrin <philip@cog.systems> Tested-by: Neil Dick <neil@cog.systems> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- arch/arm/mm/dump.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/arm/mm/dump.c +++ b/arch/arm/mm/dump.c @@ -126,8 +126,8 @@ static const struct prot_bits section_bi .val = PMD_SECT_USER, .set = "USR", }, { - .mask = L_PMD_SECT_RDONLY, - .val = L_PMD_SECT_RDONLY, + .mask = L_PMD_SECT_RDONLY | PMD_SECT_AP2, + .val = L_PMD_SECT_RDONLY | PMD_SECT_AP2, .set = "ro", .clear = "RW", #elif __LINUX_ARM_ARCH__ >= 6