From: Michal Hocko <mhocko@xxxxxxx>
Subject: memcg: oom_notify use-after-free fix
Paul Furtado has reported the following GPF:
general protection fault: 0000 [#1] SMP
Modules linked in: ipv6 dm_mod xen_netfront coretemp hwmon x86_pkg_temp_thermal crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel ablk_helper cryptd lrw gf128mul glue_helper aes_x86_64 microcode pcspkr ext4 jbd2 mbcache raid0 xen_blkfront
CPU: 3 PID: 3062 Comm: java Not tainted 3.16.0-rc5 #1
task: ffff8801cfe8f170 ti: ffff8801d2ec4000 task.ti: ffff8801d2ec4000
RIP: e030:[<ffffffff811c0b80>] [<ffffffff811c0b80>] mem_cgroup_oom_synchronize+0x140/0x240
RSP: e02b:ffff8801d2ec7d48 EFLAGS: 00010283
RAX: 0000000000000001 RBX: ffff88009d633800 RCX: 000000000000000e
RDX: fffffffffffffffe RSI: ffff88009d630200 RDI: ffff88009d630200
RBP: ffff8801d2ec7da8 R08: 0000000000000012 R09: 00000000fffffffe
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88009d633800
R13: ffff8801d2ec7d48 R14: dead000000100100 R15: ffff88009d633a30
FS: 00007f1748bb4700(0000) GS:ffff8801def80000(0000) knlGS:0000000000000000
CS: e033 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007f4110300308 CR3: 00000000c05f7000 CR4: 0000000000002660
Stack:
ffff88009d633800 0000000000000000 ffff8801cfe8f170 ffffffff811bae10
ffffffff81ca73f8 ffffffff81ca73f8 ffff8801d2ec7dc8 0000000000000006
00000000e3b30000 00000000e3b30000 ffff8801d2ec7f58 0000000000000001
Call Trace:
[<ffffffff811bae10>] ? mem_cgroup_wait_acct_move+0x110/0x110
[<ffffffff81159628>] pagefault_out_of_memory+0x18/0x90
[<ffffffff8105cee9>] mm_fault_error+0xa9/0x1a0
[<ffffffff8105d488>] __do_page_fault+0x478/0x4c0
[<ffffffff81004f00>] ? xen_mc_flush+0xb0/0x1b0
[<ffffffff81003ab3>] ? xen_write_msr_safe+0xa3/0xd0
[<ffffffff81012a40>] ? __switch_to+0x2d0/0x600
[<ffffffff8109e273>] ? finish_task_switch+0x53/0xf0
[<ffffffff81643b0a>] ? __schedule+0x37a/0x6d0
[<ffffffff8105d5dc>] do_page_fault+0x2c/0x40
[<ffffffff81649858>] page_fault+0x28/0x30
Code: 44 00 00 48 89 df e8 40 ca ff ff 48 85 c0 49 89 c4 74 35 4c 8b b0 30 02 00 00 4c 8d b8 30 02 00 00 4d 39 fe 74 1b 0f 1f 44 00 00 <49> 8b 7e 10 be 01 00 00 00 e8 42 d2 04 00 4d 8b 36 4d 39 fe 75
RIP [<ffffffff811c0b80>] mem_cgroup_oom_synchronize+0x140/0x240
RSP <ffff8801d2ec7d48>
fb2a6fc56be6 ("mm: memcg: rework and document OOM waiting and wakeup") has
moved mem_cgroup_oom_notify outside of memcg_oom_lock assuming it is
protected by the hierarchical OOM-lock. Although this is true for the
notification part the protection doesn't cover unregistration of event
which can happen in parallel now so mem_cgroup_oom_notify can see already
unlinked and/or freed mem_cgroup_eventfd_list.
Fix this by using memcg_oom_lock also in mem_cgroup_oom_notify.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=80881
Fixes: fb2a6fc56be6 (mm: memcg: rework and document OOM waiting and wakeup)
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Reported-by: Paul Furtado <paulfurtado91@xxxxxxxxx>
Tested-by: Paul Furtado <paulfurtado91@xxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.12+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 4 ++++
1 file changed, 4 insertions(+)
diff -puN mm/memcontrol.c~memcg-oom_notify-use-after-free-fix mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-oom_notify-use-after-free-fix
+++ a/mm/memcontrol.c
@@ -5415,8 +5415,12 @@ static int mem_cgroup_oom_notify_cb(stru
{
struct mem_cgroup_eventfd_list *ev;
+ spin_lock(&memcg_oom_lock);
+
list_for_each_entry(ev, &memcg->oom_notify, list)
eventfd_signal(ev->eventfd, 1);
+
+ spin_unlock(&memcg_oom_lock);
return 0;
}
_
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