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authorRoman Gushchin <guro@fb.com>2018-11-02 15:47:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-11-03 10:09:37 -0700
commite68599a3c3ad0f3171a7cb4e48aa6f9a69381902 (patch)
tree8875f414c9f0acbf22857484d1cb32a0804ca92f
parent5f21585384a4a69b8bfdd2cae7e3648ae805f57d (diff)
downloadlinux-e68599a3c3ad0f3171a7cb4e48aa6f9a69381902.tar.gz
mm: handle no memcg case in memcg_kmem_charge() properly
Mike Galbraith reported a regression caused by the commit 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") on a system with "cgroup_disable=memory" boot option: the system panics with the following stack trace: BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8 PGD 0 P4D 0 Oops: 0002 [#1] PREEMPT SMP PTI CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fed4 RIP: 0010:page_counter_try_charge+0x22/0xc0 Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 Call Trace: try_charge+0xcb/0x780 memcg_kmem_charge_memcg+0x28/0x80 memcg_kmem_charge+0x8b/0x1d0 copy_process.part.41+0x1ca/0x2070 _do_fork+0xd7/0x3d0 do_syscall_64+0x5a/0x180 entry_SYSCALL_64_after_hwframe+0x49/0xbe The problem occurs because get_mem_cgroup_from_current() returns the NULL pointer if memory controller is disabled. Let's check if this is a case at the beginning of memcg_kmem_charge() and just return 0 if mem_cgroup_disabled() returns true. This is how we handle this case in many other places in the memory controller code. Link: http://lkml.kernel.org/r/20181029215123.17830-1-guro@fb.com Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") Signed-off-by: Roman Gushchin <guro@fb.com> Reported-by: Mike Galbraith <efault@gmx.de> Acked-by: Rik van Riel <riel@surriel.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Shakeel Butt <shakeelb@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/memcontrol.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 54920cbc46bf..6e1469b80cb7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2593,7 +2593,7 @@ int memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
struct mem_cgroup *memcg;
int ret = 0;
- if (memcg_kmem_bypass())
+ if (mem_cgroup_disabled() || memcg_kmem_bypass())
return 0;
memcg = get_mem_cgroup_from_current();