From: Michal Hocko <mhocko@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
LKML <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Michal Hocko <mhocko@suse.com>,
Thomas Lindroth <thomas.lindroth@gmail.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Subject: [PATCH] memcg, kmem: do not fail __GFP_NOFAIL charges
Date: Fri, 6 Sep 2019 14:56:08 +0200 [thread overview]
Message-ID: <20190906125608.32129-1-mhocko@kernel.org> (raw)
In-Reply-To: <31131c2d-a936-8bbf-e58d-a3baaa457340@gmail.com>
From: Michal Hocko <mhocko@suse.com>
Thomas has noticed the following NULL ptr dereference when using cgroup
v1 kmem limit:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
PGD 0
P4D 0
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 3 PID: 16923 Comm: gtk-update-icon Not tainted 4.19.51 #42
Hardware name: Gigabyte Technology Co., Ltd. Z97X-Gaming G1/Z97X-Gaming G1, BIOS F9 07/31/2015
RIP: 0010:create_empty_buffers+0x24/0x100
Code: cd 0f 1f 44 00 00 0f 1f 44 00 00 41 54 49 89 d4 ba 01 00 00 00 55 53 48 89 fb e8 97 fe ff ff 48 89 c5 48 89 c2 eb 03 48 89 ca <48> 8b 4a 08 4c 09 22 48 85 c9 75 f1 48 89 6a 08 48 8b 43 18 48 8d
RSP: 0018:ffff927ac1b37bf8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: fffff2d4429fd740 RCX: 0000000100097149
RDX: 0000000000000000 RSI: 0000000000000082 RDI: ffff9075a99fbe00
RBP: 0000000000000000 R08: fffff2d440949cc8 R09: 00000000000960c0
R10: 0000000000000002 R11: 0000000000000000 R12: 0000000000000000
R13: ffff907601f18360 R14: 0000000000002000 R15: 0000000000001000
FS: 00007fb55b288bc0(0000) GS:ffff90761f8c0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 000000007aebc002 CR4: 00000000001606e0
Call Trace:
create_page_buffers+0x4d/0x60
__block_write_begin_int+0x8e/0x5a0
? ext4_inode_attach_jinode.part.82+0xb0/0xb0
? jbd2__journal_start+0xd7/0x1f0
ext4_da_write_begin+0x112/0x3d0
generic_perform_write+0xf1/0x1b0
? file_update_time+0x70/0x140
__generic_file_write_iter+0x141/0x1a0
ext4_file_write_iter+0xef/0x3b0
__vfs_write+0x17e/0x1e0
vfs_write+0xa5/0x1a0
ksys_write+0x57/0xd0
do_syscall_64+0x55/0x160
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Tetsuo then noticed that this is because the __memcg_kmem_charge_memcg
fails __GFP_NOFAIL charge when the kmem limit is reached. This is a
wrong behavior because nofail allocations are not allowed to fail.
Normal charge path simply forces the charge even if that means to cross
the limit. Kmem accounting should be doing the same.
Reported-by: Thomas Lindroth <thomas.lindroth@gmail.com>
Debugged-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: stable
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
mm/memcontrol.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9ec5e12486a7..e18108b2b786 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2821,6 +2821,16 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
!page_counter_try_charge(&memcg->kmem, nr_pages, &counter)) {
+
+ /*
+ * Enforce __GFP_NOFAIL allocation because callers are not
+ * prepared to see failures and likely do not have any failure
+ * handling code.
+ */
+ if (gfp & __GFP_NOFAIL) {
+ page_counter_charge(&memcg->kmem, nr_pages);
+ return 0;
+ }
cancel_charge(memcg, nr_pages);
return -ENOMEM;
}
--
2.20.1
next parent reply other threads:[~2019-09-06 12:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <31131c2d-a936-8bbf-e58d-a3baaa457340@gmail.com>
2019-09-06 12:56 ` Michal Hocko [this message]
2019-09-06 18:24 ` [PATCH] memcg, kmem: do not fail __GFP_NOFAIL charges Shakeel Butt
2019-09-09 11:22 ` Michal Hocko
2019-09-11 12:00 ` Michal Hocko
2019-09-11 14:37 ` Andrew Morton
2019-09-11 15:16 ` Michal Hocko
2019-09-13 2:46 ` Shakeel Butt
2019-09-24 10:53 ` Michal Hocko
2019-09-24 23:06 ` Andrew Morton
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