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Subject[PATCH] clone3: add build-time CLONE_ARGS_SIZE_VER* validity checks
CLONE_ARGS_SIZE_VER* macros are defined explicitly and not via
the offsets of the relevant struct clone_args fields, which makes
it rather error-prone, so it probably makes sense to add some
compile-time checks for them (including the one that breaks
on struct clone_args extension as a reminder to add a relevant
size macro and a similar check). Function copy_clone_args_from_user
seems to be a good place for such checks.

Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
---
kernel/fork.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/kernel/fork.c b/kernel/fork.c
index b4f7775..11bcc7e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2605,6 +2605,14 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
struct clone_args args;
pid_t *kset_tid = kargs->set_tid;

+ BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
+ CLONE_ARGS_SIZE_VER0);
+ BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
+ CLONE_ARGS_SIZE_VER1);
+ BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
+ CLONE_ARGS_SIZE_VER2);
+ BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
+
if (unlikely(usize > PAGE_SIZE))
return -E2BIG;
if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
--
2.1.4
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