Add vmalloc tagging support to HW_TAGS KASAN.
The key difference between HW_TAGS and the other two KASAN modes when it
comes to vmalloc: HW_TAGS KASAN can only assign tags to physical memory.
The other two modes have shadow memory covering every mapped virtual
memory region.
Make __kasan_unpoison_vmalloc() for HW_TAGS KASAN:
- Skip non-VM_ALLOC mappings as HW_TAGS KASAN can only tag a single
mapping of normal physical memory; see the comment in the function.
- Generate a random tag, tag the returned pointer and the allocation,
and initialize the allocation at the same time.
- Propagate the tag into the page stucts to allow accesses through
page_address(vmalloc_to_page()).
The rest of vmalloc-related KASAN hooks are not needed:
- The shadow-related ones are fully skipped.
- __kasan_poison_vmalloc() is kept as a no-op with a comment.
Poisoning and zeroing of physical pages that are backing vmalloc()
allocations are skipped via __GFP_SKIP_KASAN_UNPOISON and
__GFP_SKIP_ZERO: __kasan_unpoison_vmalloc() does that instead.
Enabling CONFIG_KASAN_VMALLOC with HW_TAGS is not yet allowed.
Link: https://lkml.kernel.org/r/d19b2e9e59a9abc59d05b72dea8429dcaea739c6.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <[email protected]>
Co-developed-by: Vincenzo Frascino <[email protected]>
Signed-off-by: Vincenzo Frascino <[email protected]>
Acked-by: Marco Elver <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Evgenii Stepanov <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Peter Collingbourne <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
The kernel currently uses kmem_cache to allocate shadow call stacks,
which means an overflows may not be immediately detected and can
potentially result in another task's shadow stack to be overwritten.
This change switches SCS to use virtually mapped shadow stacks for
tasks, which increases shadow stack size to a full page and provides
more robust overflow detection, similarly to VMAP_STACK.
Signed-off-by: Sami Tolvanen <[email protected]>
Acked-by: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>
Currently the kernel stack is being accounted per-zone. There is no need
to do that. In addition due to being per-zone, memcg has to keep a
separate MEMCG_KERNEL_STACK_KB. Make the stat per-node and deprecate
MEMCG_KERNEL_STACK_KB as memcg_stat_item is an extension of
node_stat_item. In addition localize the kernel stack stats updates to
account_kernel_stack().
Signed-off-by: Shakeel Butt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Roman Gushchin <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
Fix the SCS debug usage check so that we report the number of bytes
used, rather than the number of entries.
Fixes: 5bbaf9d1fc ("scs: Add support for stack usage debugging")
Reported-by: Sami Tolvanen <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
asm/scs.h is no longer needed by the core code, so remove a redundant
header inclusion and update the stale Kconfig text.
Tested-by: Sami Tolvanen <[email protected]>
Reviewed-by: Mark Rutland <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
There is nothing architecture-specific about scs_overflow_check() as
it's just a trivial wrapper around scs_corrupted().
For parity with task_stack_end_corrupted(), rename scs_corrupted() to
task_scs_end_corrupted() and call it from schedule_debug() when
CONFIG_SCHED_STACK_END_CHECK_is enabled, which better reflects its
purpose as a debug feature to catch inadvertent overflow of the SCS.
Finally, remove the unused scs_overflow_check() function entirely.
This has absolutely no impact on architectures that do not support SCS
(currently arm64 only).
Tested-by: Sami Tolvanen <[email protected]>
Reviewed-by: Mark Rutland <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
There's no need to perform the shadow stack page accounting independently
of the lifetime of the underlying allocation, so call the accounting code
from the {alloc,free}() functions and simplify the code in the process.
Tested-by: Sami Tolvanen <[email protected]>
Reviewed-by: Mark Rutland <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Storing the SCS information in thread_info as a {base,offset} pair
introduces an additional load instruction on the ret-to-user path,
since the SCS stack pointer in x18 has to be converted back to an offset
by subtracting the base.
Replace the offset with the absolute SCS stack pointer value instead
and avoid the redundant load.
Tested-by: Sami Tolvanen <[email protected]>
Reviewed-by: Mark Rutland <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Implements CONFIG_DEBUG_STACK_USAGE for shadow stacks. When enabled,
also prints out the highest shadow stack usage per process.
Signed-off-by: Sami Tolvanen <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Acked-by: Will Deacon <[email protected]>
[will: rewrote most of scs_check_usage()]
Signed-off-by: Will Deacon <[email protected]>
This change adds generic support for Clang's Shadow Call Stack,
which uses a shadow stack to protect return addresses from being
overwritten by an attacker. Details are available here:
https://clang.llvm.org/docs/ShadowCallStack.html
Note that security guarantees in the kernel differ from the ones
documented for user space. The kernel must store addresses of
shadow stacks in memory, which means an attacker capable reading
and writing arbitrary memory may be able to locate them and hijack
control flow by modifying the stacks.
Signed-off-by: Sami Tolvanen <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Miguel Ojeda <[email protected]>
[will: Numerous cosmetic changes]
Signed-off-by: Will Deacon <[email protected]>
Andrey Konovalov