From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit ad0f75e5f57ccbceec13274e1e242f2b5a6397ed ]
When we clone a socket in sk_clone_lock(), its sk_cgrp_data is copied, so the cgroup refcnt must be taken too. And, unlike the sk_alloc() path, sock_update_netprioidx() is not called here. Therefore, it is safe and necessary to grab the cgroup refcnt even when cgroup_sk_alloc is disabled.
sk_clone_lock() is in BH context anyway, the in_interrupt() would terminate this function if called there. And for sk_alloc() skcd->val is always zero. So it's safe to factor out the code to make it more readable.
The global variable 'cgroup_sk_alloc_disabled' is used to determine whether to take these reference counts. It is impossible to make the reference counting correct unless we save this bit of information in skcd->val. So, add a new bit there to record whether the socket has already taken the reference counts. This obviously relies on kmalloc() to align cgroup pointers to at least 4 bytes, ARCH_KMALLOC_MINALIGN is certainly larger than that.
This bug seems to be introduced since the beginning, commit d979a39d7242 ("cgroup: duplicate cgroup reference when cloning sockets") tried to fix it but not compeletely. It seems not easy to trigger until the recent commit 090e28b229af ("netprio_cgroup: Fix unlimited memory leak of v2 cgroups") was merged.
Fixes: bd1060a1d671 ("sock, cgroup: add sock->sk_cgroup") Reported-by: Cameron Berkenpas cam@neo-zeon.de Reported-by: Peter Geis pgwipeout@gmail.com Reported-by: Lu Fengqi lufq.fnst@cn.fujitsu.com Reported-by: Daniël Sonck dsonck92@gmail.com Reported-by: Zhang Qiang qiang.zhang@windriver.com Tested-by: Cameron Berkenpas cam@neo-zeon.de Tested-by: Peter Geis pgwipeout@gmail.com Tested-by: Thomas Lamprecht t.lamprecht@proxmox.com Cc: Daniel Borkmann daniel@iogearbox.net Cc: Zefan Li lizefan@huawei.com Cc: Tejun Heo tj@kernel.org Cc: Roman Gushchin guro@fb.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/cgroup-defs.h | 6 ++++-- include/linux/cgroup.h | 4 +++- kernel/cgroup/cgroup.c | 31 +++++++++++++++++++------------ net/core/sock.c | 2 +- 4 files changed, 27 insertions(+), 16 deletions(-)
--- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -797,7 +797,8 @@ struct sock_cgroup_data { union { #ifdef __LITTLE_ENDIAN struct { - u8 is_data; + u8 is_data : 1; + u8 no_refcnt : 1; u8 padding; u16 prioidx; u32 classid; @@ -807,7 +808,8 @@ struct sock_cgroup_data { u32 classid; u16 prioidx; u8 padding; - u8 is_data; + u8 no_refcnt : 1; + u8 is_data : 1; } __packed; #endif u64 val; --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -822,6 +822,7 @@ extern spinlock_t cgroup_sk_update_lock;
void cgroup_sk_alloc_disable(void); void cgroup_sk_alloc(struct sock_cgroup_data *skcd); +void cgroup_sk_clone(struct sock_cgroup_data *skcd); void cgroup_sk_free(struct sock_cgroup_data *skcd);
static inline struct cgroup *sock_cgroup_ptr(struct sock_cgroup_data *skcd) @@ -835,7 +836,7 @@ static inline struct cgroup *sock_cgroup */ v = READ_ONCE(skcd->val);
- if (v & 1) + if (v & 3) return &cgrp_dfl_root.cgrp;
return (struct cgroup *)(unsigned long)v ?: &cgrp_dfl_root.cgrp; @@ -847,6 +848,7 @@ static inline struct cgroup *sock_cgroup #else /* CONFIG_CGROUP_DATA */
static inline void cgroup_sk_alloc(struct sock_cgroup_data *skcd) {} +static inline void cgroup_sk_clone(struct sock_cgroup_data *skcd) {} static inline void cgroup_sk_free(struct sock_cgroup_data *skcd) {}
#endif /* CONFIG_CGROUP_DATA */ --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6379,18 +6379,8 @@ void cgroup_sk_alloc_disable(void)
void cgroup_sk_alloc(struct sock_cgroup_data *skcd) { - if (cgroup_sk_alloc_disabled) - return; - - /* Socket clone path */ - if (skcd->val) { - /* - * We might be cloning a socket which is left in an empty - * cgroup and the cgroup might have already been rmdir'd. - * Don't use cgroup_get_live(). - */ - cgroup_get(sock_cgroup_ptr(skcd)); - cgroup_bpf_get(sock_cgroup_ptr(skcd)); + if (cgroup_sk_alloc_disabled) { + skcd->no_refcnt = 1; return; }
@@ -6415,10 +6405,27 @@ void cgroup_sk_alloc(struct sock_cgroup_ rcu_read_unlock(); }
+void cgroup_sk_clone(struct sock_cgroup_data *skcd) +{ + if (skcd->val) { + if (skcd->no_refcnt) + return; + /* + * We might be cloning a socket which is left in an empty + * cgroup and the cgroup might have already been rmdir'd. + * Don't use cgroup_get_live(). + */ + cgroup_get(sock_cgroup_ptr(skcd)); + cgroup_bpf_get(sock_cgroup_ptr(skcd)); + } +} + void cgroup_sk_free(struct sock_cgroup_data *skcd) { struct cgroup *cgrp = sock_cgroup_ptr(skcd);
+ if (skcd->no_refcnt) + return; cgroup_bpf_put(cgrp); cgroup_put(cgrp); } --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1837,7 +1837,7 @@ struct sock *sk_clone_lock(const struct /* sk->sk_memcg will be populated at accept() time */ newsk->sk_memcg = NULL;
- cgroup_sk_alloc(&newsk->sk_cgrp_data); + cgroup_sk_clone(&newsk->sk_cgrp_data);
rcu_read_lock(); filter = rcu_dereference(sk->sk_filter);