From ad0f75e5f57ccbceec13274e1e242f2b5a6397ed Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Thu, 2 Jul 2020 11:52:56 -0700 Subject: cgroup: fix cgroup_sk_alloc() for sk_clone_lock() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reported-by: Peter Geis Reported-by: Lu Fengqi Reported-by: Daniël Sonck Reported-by: Zhang Qiang Tested-by: Cameron Berkenpas Tested-by: Peter Geis Tested-by: Thomas Lamprecht Cc: Daniel Borkmann Cc: Zefan Li Cc: Tejun Heo Cc: Roman Gushchin Signed-off-by: Cong Wang Signed-off-by: David S. Miller --- include/linux/cgroup-defs.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include/linux/cgroup-defs.h') diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 52661155f85f..4f1cd0edc57d 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -790,7 +790,8 @@ 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; @@ -800,7 +801,8 @@ 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; -- cgit From 14b032b8f8fce03a546dcf365454bec8c4a58d7d Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Thu, 9 Jul 2020 16:28:44 -0700 Subject: cgroup: Fix sock_cgroup_data on big-endian. In order for no_refcnt and is_data to be the lowest order two bits in the 'val' we have to pad out the bitfield of the u8. Fixes: ad0f75e5f57c ("cgroup: fix cgroup_sk_alloc() for sk_clone_lock()") Reported-by: Guenter Roeck Signed-off-by: David S. Miller --- include/linux/cgroup-defs.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/cgroup-defs.h') diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 4f1cd0edc57d..fee0b5547cd0 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -792,6 +792,7 @@ struct sock_cgroup_data { struct { u8 is_data : 1; u8 no_refcnt : 1; + u8 unused : 6; u8 padding; u16 prioidx; u32 classid; @@ -801,6 +802,7 @@ struct sock_cgroup_data { u32 classid; u16 prioidx; u8 padding; + u8 unused : 6; u8 no_refcnt : 1; u8 is_data : 1; } __packed; -- cgit