From e82a118f57b89bbb437ce70780fc2678d5c281e5 Mon Sep 17 00:00:00 2001 From: Eugene Syromiatnikov Date: Sun, 12 Apr 2020 22:25:33 +0200 Subject: clone3: fix cgroup argument sanity check Checking that cgroup field value of struct clone_args is less than 0 is useless, as it is defined as unsigned 64-bit integer. Moreover, it doesn't catch the situations where its higher bits are lost during the assignment to the cgroup field of the cgroup field of the internal struct kernel_clone_args (where it is declared as signed 32-bit integer), so it is still possible to pass garbage there. A check against INT_MAX solves both these issues. Fixes: ef2c41cf38a7559b ("clone3: allow spawning processes into cgroups") Signed-off-by: Eugene Syromiatnikov Acked-by: Christian Brauner Link: https://lore.kernel.org/r/20200412202533.GA29554@asgard.redhat.com Signed-off-by: Christian Brauner --- kernel/fork.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 4385f3d639f2..b4f7775623c8 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2631,7 +2631,7 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, !valid_signal(args.exit_signal))) return -EINVAL; - if ((args.flags & CLONE_INTO_CGROUP) && args.cgroup < 0) + if ((args.flags & CLONE_INTO_CGROUP) && args.cgroup > INT_MAX) return -EINVAL; *kargs = (struct kernel_clone_args){ -- cgit v1.2.3-70-g09d2 From 62173872ca65767c586217dec0a32485da8a2f07 Mon Sep 17 00:00:00 2001 From: Eugene Syromiatnikov Date: Sun, 12 Apr 2020 22:31:23 +0200 Subject: clone3: add a check for the user struct size if CLONE_INTO_CGROUP is set Passing CLONE_INTO_CGROUP with an under-sized structure (that doesn't properly contain cgroup field) seems like garbage input, especially considering the fact that fd 0 is a valid descriptor. Signed-off-by: Eugene Syromiatnikov Acked-by: Christian Brauner Link: https://lore.kernel.org/r/20200412203123.GA5869@asgard.redhat.com Signed-off-by: Christian Brauner --- kernel/fork.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index b4f7775623c8..3ab7cf88e455 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2631,7 +2631,8 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, !valid_signal(args.exit_signal))) return -EINVAL; - if ((args.flags & CLONE_INTO_CGROUP) && args.cgroup > INT_MAX) + if ((args.flags & CLONE_INTO_CGROUP) && + (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2)) return -EINVAL; *kargs = (struct kernel_clone_args){ -- cgit v1.2.3-70-g09d2 From a966dcfe153ab0a3d8d79cd971a079411a489be7 Mon Sep 17 00:00:00 2001 From: Eugene Syromiatnikov Date: Sun, 12 Apr 2020 22:26:58 +0200 Subject: 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 Acked-by: Christian Brauner Link: https://lore.kernel.org/r/20200412202658.GA31499@asgard.redhat.com Signed-off-by: Christian Brauner --- kernel/fork.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 3ab7cf88e455..8c700f881d92 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)) -- cgit v1.2.3-70-g09d2