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author | 2017-08-16 13:00:58 -0700 | |
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committer | 2018-01-15 12:08:04 -0800 | |
commit | 5905429ad85657c28d93ec3d826ddeea1f44c3ce (patch) | |
tree | 57fe66f71ea19aa2305ee2085bdd1809e946a136 /arch/Kconfig | |
parent | fork: Define usercopy region in thread_stack slab caches (diff) | |
download | linux-5905429ad85657c28d93ec3d826ddeea1f44c3ce.tar.gz linux-5905429ad85657c28d93ec3d826ddeea1f44c3ce.tar.bz2 linux-5905429ad85657c28d93ec3d826ddeea1f44c3ce.zip |
fork: Provide usercopy whitelisting for task_struct
While the blocked and saved_sigmask fields of task_struct are copied to
userspace (via sigmask_to_save() and setup_rt_frame()), it is always
copied with a static length (i.e. sizeof(sigset_t)).
The only portion of task_struct that is potentially dynamically sized and
may be copied to userspace is in the architecture-specific thread_struct
at the end of task_struct.
cache object allocation:
kernel/fork.c:
alloc_task_struct_node(...):
return kmem_cache_alloc_node(task_struct_cachep, ...);
dup_task_struct(...):
...
tsk = alloc_task_struct_node(node);
copy_process(...):
...
dup_task_struct(...)
_do_fork(...):
...
copy_process(...)
example usage trace:
arch/x86/kernel/fpu/signal.c:
__fpu__restore_sig(...):
...
struct task_struct *tsk = current;
struct fpu *fpu = &tsk->thread.fpu;
...
__copy_from_user(&fpu->state.xsave, ..., state_size);
fpu__restore_sig(...):
...
return __fpu__restore_sig(...);
arch/x86/kernel/signal.c:
restore_sigcontext(...):
...
fpu__restore_sig(...)
This introduces arch_thread_struct_whitelist() to let an architecture
declare specifically where the whitelist should be within thread_struct.
If undefined, the entire thread_struct field is left whitelisted.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: "Mickaël Salaün" <mic@digikod.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Rik van Riel <riel@redhat.com>
Diffstat (limited to 'arch/Kconfig')
-rw-r--r-- | arch/Kconfig | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 400b9e1b2f27..8911ff37335a 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -242,6 +242,17 @@ config ARCH_INIT_TASK config ARCH_TASK_STRUCT_ALLOCATOR bool +config HAVE_ARCH_THREAD_STRUCT_WHITELIST + bool + depends on !ARCH_TASK_STRUCT_ALLOCATOR + help + An architecture should select this to provide hardened usercopy + knowledge about what region of the thread_struct should be + whitelisted for copying to userspace. Normally this is only the + FPU registers. Specifically, arch_thread_struct_whitelist() + should be implemented. Without this, the entire thread_struct + field in task_struct will be left whitelisted. + # Select if arch has its private alloc_thread_stack() function config ARCH_THREAD_STACK_ALLOCATOR bool |