6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook <keescook@xxxxxxxxxxxx> [ Upstream commit b69f0aeb068980af983d399deafc7477cec8bc04 ] For pid namespaces, struct pid uses a dynamically sized array member, "numbers". This was implemented using the ancient 1-element fake flexible array, which has been deprecated for decades. Replace it with a C99 flexible array, refactor the array size calculations to use struct_size(), and address elements via indexes. Note that the static initializer (which defines a single element) works as-is, and requires no special handling. Without this, CONFIG_UBSAN_BOUNDS (and potentially CONFIG_FORTIFY_SOURCE) will trigger bounds checks: https://lore.kernel.org/lkml/20230517-bushaltestelle-super-e223978c1ba6@brauner Cc: Christian Brauner <brauner@xxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Jeff Xu <jeffxu@xxxxxxxxxx> Cc: Andreas Gruenbacher <agruenba@xxxxxxxxxx> Cc: Daniel Verkamp <dverkamp@xxxxxxxxxxxx> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> Cc: Jeff Xu <jeffxu@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Boqun Feng <boqun.feng@xxxxxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: Frederic Weisbecker <frederic@xxxxxxxxxx> Reported-by: syzbot+ac3b41786a2d0565b6d5@xxxxxxxxxxxxxxxxxxxxxxxxx [brauner: dropped unrelated changes and remove 0 with NULL cast] Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- include/linux/pid.h | 2 +- kernel/pid.c | 7 +++++-- kernel/pid_namespace.c | 2 +- 3 files changed, 7 insertions(+), 4 deletions(-) diff --git a/include/linux/pid.h b/include/linux/pid.h index 343abf22092e6..bf3af54de6165 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -67,7 +67,7 @@ struct pid /* wait queue for pidfd notifications */ wait_queue_head_t wait_pidfd; struct rcu_head rcu; - struct upid numbers[1]; + struct upid numbers[]; }; extern struct pid init_struct_pid; diff --git a/kernel/pid.c b/kernel/pid.c index 3fbc5e46b7217..74834c04a0818 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -661,8 +661,11 @@ void __init pid_idr_init(void) idr_init(&init_pid_ns.idr); - init_pid_ns.pid_cachep = KMEM_CACHE(pid, - SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT); + init_pid_ns.pid_cachep = kmem_cache_create("pid", + struct_size((struct pid *)NULL, numbers, 1), + __alignof__(struct pid), + SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, + NULL); } static struct file *__pidfd_fget(struct task_struct *task, int fd) diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index 1daadbefcee3a..a575fabf697eb 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -47,7 +47,7 @@ static struct kmem_cache *create_pid_cachep(unsigned int level) return kc; snprintf(name, sizeof(name), "pid_%u", level + 1); - len = sizeof(struct pid) + level * sizeof(struct upid); + len = struct_size((struct pid *)NULL, numbers, level + 1); mutex_lock(&pid_caches_mutex); /* Name collision forces to do allocation under mutex. */ if (!*pkc) -- 2.43.0
