Page mappings with full RWX permissions are a security risk.
x86, arm64 has an option to walk the page tables
and dump any bad pages.
(1404d6f13e
("arm64: dump: Add checking for writable and exectuable pages"))
Add a similar implementation for arm.
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This patch makes the page table dumping seq_file optional.
It makes the page table dumping code usable for other cases.
This patch refers below commit of arm64.
(ae5d1cf358
("arm64: dump: Make the page table dumping seq_file optional"))
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Laura Abbott <labbott@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This patch refactors the arm page table dumping code,
so multiple tables may be registered with the framework.
This patch refers below commits of arm64.
(4674fdb9f1 ("arm64: mm: dump: make page table dumping reusable"))
(4ddb9bf833 ("arm64: dump: Make ptdump debugfs a separate option"))
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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: ded9477984 ("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@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This adds the memory domain (on non-LPAE) to the PMD and PTE dumps. This
isn't in the regular PMD bits because I couldn't find a clean way to
fall back to retain some of the PMD bits when reporting PTE. So this is
special-cased currently.
New output example:
---[ Modules ]---
0x7f000000-0x7f001000 4K KERNEL ro x SHD MEM/CACHED/WBWA
0x7f001000-0x7f002000 4K KERNEL ro NX SHD MEM/CACHED/WBWA
0x7f002000-0x7f004000 8K KERNEL RW NX SHD MEM/CACHED/WBWA
---[ Kernel Mapping ]---
0x80000000-0x80100000 1M KERNEL RW NX SHD
0x80100000-0x80800000 7M KERNEL ro x SHD
0x80800000-0x80b00000 3M KERNEL ro NX SHD
0x80b00000-0xa0000000 501M KERNEL RW NX SHD
...
---[ Vectors ]---
0xffff0000-0xffff1000 4K VECTORS USR ro x SHD MEM/CACHED/WBWA
0xffff1000-0xffff2000 4K VECTORS ro x SHD MEM/CACHED/WBWA
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
For MMU configurations, VECTORS_BASE is always 0xffff0000, a macro
definition will suffice.
For no-MMU, exception base address is dynamically determined in
subsequent patches. To preserve bisectability, now make the
macro applicable for no-MMU scenario too.
Thanks to 0-DAY kernel test infrastructure that found the
bisectability issue. This macro will be restricted to MMU case upon
dynamically determining exception base address for no-MMU.
Once exception address is handled dynamically for no-MMU,
VECTORS_BASE can be removed from Kconfig.
Signed-off-by: afzal mohammed <afzal.mohd.ma@gmail.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Currently the arm page table dumping code starts dumping page tables
from USER_PGTABLES_CEILING. This is unnecessary for skipping any entries
related to userspace as the swapper_pg_dir does not contain such
entries, and results in a couple of unfortuante side effects.
Firstly, any kernel mappings which might exist below
USER_PGTABLES_CEILING will not be accounted in the dump output. This
masks any entries erroneously created below this address.
Secondly, if the final page table entry walked is part of a valid
mapping the page table dumping code will not log the region this entry
is part of, as the final note_page call in walk_pgd will trigger an
early return when 0 < USER_PGTABLES_CEILING. Luckily this isn't seen on
contemporary systems as they typically don't have enough RAM to extend
the linear mapping right to the end of the address space.
Due to the way addr is constructed in the walk_* functions, it can never
be less than USER_PGTABLES_CEILING when walking the page tables, so it
is not necessary to avoid dereferencing invalid table addresses. The
existing checks for st->current_prot and st->marker[1].start_address are
sufficient to ensure we will not print and/or dereference garbage when
trying to log information.
This patch removes both problematic uses of USER_PGTABLES_CEILING from
the arm page table dumping code, preventing both of these issues. We
will now report any low mappings, and the final note_page call will not
return early, ensuring all regions are logged.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
For LPAE, we have the following means for encoding writable or dirty
ptes:
L_PTE_DIRTY L_PTE_RDONLY
!pte_dirty && !pte_write 0 1
!pte_dirty && pte_write 0 1
pte_dirty && !pte_write 1 1
pte_dirty && pte_write 1 0
So we can't distinguish between writeable clean ptes and read only
ptes. This can cause problems with ptes being incorrectly flagged as
read only when they are writeable but not dirty.
This patch renumbers L_PTE_RDONLY from AP[2] to a software bit #58,
and adds additional logic to set AP[2] whenever the pte is read only
or not dirty. That way we can distinguish between clean writeable ptes
and read only ptes.
HugeTLB pages will use this new logic automatically.
We need to add some logic to Transparent HugePages to ensure that they
correctly interpret the revised pgprot permissions (L_PTE_RDONLY has
moved and no longer matches PMD_SECT_AP2). In the process of revising
THP, the names of the PMD software bits have been prefixed with L_ to
make them easier to distinguish from their hardware bit counterparts.
Signed-off-by: Steve Capper <steve.capper@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
On non-LPAE ARMv6+, read-only PMD bits are defined with the combination
"PMD_SECT_APX | PMD_SECT_AP_WRITE". Adjusted the bit masks to correctly
report this.
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
On 2-level page table systems, the PMD has 2 section entries. Report
these, otherwise ARM_PTDUMP will miss reporting permission changes on
odd section boundaries.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Steve Capper <steve.capper@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This patch allows the kernel page tables to be dumped via a debugfs file,
allowing kernel developers to check the layout of the kernel page tables
and the verify the various permissions and type settings.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Jinbum Park