diff options
| author | Roman Gushchin <guro@fb.com> | 2018-06-14 15:26:17 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-06-15 07:55:23 +0900 |
| commit | df2a419677652439b473a73c5acf32354b217cc6 (patch) | |
| tree | 88ae94d9dd67b81611754885c7a856d256ce8b07 /mm/memcontrol.c | |
| parent | 1105a2fc022f3c7482e32faf516e8bc44095f778 (diff) | |
| download | lwn-df2a419677652439b473a73c5acf32354b217cc6.tar.gz lwn-df2a419677652439b473a73c5acf32354b217cc6.zip | |
mm: fix null pointer dereference in mem_cgroup_protected
Shakeel reported a crash in mem_cgroup_protected(), which can be triggered
by memcg reclaim if the legacy cgroup v1 use_hierarchy=0 mode is used:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000120
PGD 8000001ff55da067 P4D 8000001ff55da067 PUD 1fdc7df067 PMD 0
Oops: 0000 [#4] SMP PTI
CPU: 0 PID: 15581 Comm: bash Tainted: G D 4.17.0-smp-clean #5
Hardware name: ...
RIP: 0010:mem_cgroup_protected+0x54/0x130
Code: 4c 8b 8e 00 01 00 00 4c 8b 86 08 01 00 00 48 8d 8a 08 ff ff ff 48 85 d2 ba 00 00 00 00 48 0f 44 ca 48 39 c8 0f 84 cf 00 00 00 <48> 8b 81 20 01 00 00 4d 89 ca 4c 39 c8 4c 0f 46 d0 4d 85 d2 74 05
RSP: 0000:ffffabe64dfafa58 EFLAGS: 00010286
RAX: ffff9fb6ff03d000 RBX: ffff9fb6f5b1b000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9fb6f5b1b000 RDI: ffff9fb6f5b1b000
RBP: ffffabe64dfafb08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 000000000000c800 R12: ffffabe64dfafb88
R13: ffff9fb6f5b1b000 R14: ffffabe64dfafb88 R15: ffff9fb77fffe000
FS: 00007fed1f8ac700(0000) GS:ffff9fb6ff400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000120 CR3: 0000001fdcf86003 CR4: 00000000001606f0
Call Trace:
? shrink_node+0x194/0x510
do_try_to_free_pages+0xfd/0x390
try_to_free_mem_cgroup_pages+0x123/0x210
try_charge+0x19e/0x700
mem_cgroup_try_charge+0x10b/0x1a0
wp_page_copy+0x134/0x5b0
do_wp_page+0x90/0x460
__handle_mm_fault+0x8e3/0xf30
handle_mm_fault+0xfe/0x220
__do_page_fault+0x262/0x500
do_page_fault+0x28/0xd0
? page_fault+0x8/0x30
page_fault+0x1e/0x30
RIP: 0033:0x485b72
The problem happens because parent_mem_cgroup() returns a NULL pointer,
which is dereferenced later without a check.
As cgroup v1 has no memory guarantee support, let's make
mem_cgroup_protected() immediately return MEMCG_PROT_NONE, if the given
cgroup has no parent (non-hierarchical mode is used).
Link: http://lkml.kernel.org/r/20180611175418.7007-2-guro@fb.com
Fixes: bf8d5d52ffe8 ("memcg: introduce memory.min")
Signed-off-by: Roman Gushchin <guro@fb.com>
Reported-by: Shakeel Butt <shakeelb@google.com>
Tested-by: Shakeel Butt <shakeelb@google.com>
Tested-by: John Stultz <john.stultz@linaro.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c1e64d60ed02..5a3873e9d657 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5480,6 +5480,10 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, elow = memcg->memory.low; parent = parent_mem_cgroup(memcg); + /* No parent means a non-hierarchical mode on v1 memcg */ + if (!parent) + return MEMCG_PROT_NONE; + if (parent == root) goto exit; |