[PATCH] mm: fix panic in __alloc_pages

Alexey Makhalov
2021-11-01T20:13:37Z

There is a kernel panic caused by __alloc_pages() accessing
uninitialized NODE_DATA(nid). Uninitialized node data exists
during the time when CPU with memoryless node was added but
not onlined yet. Panic can be easy reproduced by disabling
udev rule for automatic onlining hot added CPU followed by
CPU with memoryless node hot add.

This is a panic caused by percpu code doing allocations for
all possible CPUs and hitting this issue:

CPU2 has been hot-added
BUG: unable to handle page fault for address: 0000000000001608
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 1 Comm: systemd Tainted: G E 5.15.0-rc7+ #11
Hardware name: VMware, Inc. VMware7,1/440BX Desktop Reference Platform, BIOS VMW

RIP: 0010:__alloc_pages+0x127/0x290
Code: 4c 89 f0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 44 89 e0 48 8b 55 b8 c1 e8 0c 83 e0 01 88 45 d0 4c 89 c8 48 85 d2 0f 85 1a 01 00 00 <45> 3b 41 08 0f 82 10 01 00 00 48 89 45 c0 48 8b 00 44 89 e2 81 e2
RSP: 0018:ffffc900006f3bc8 EFLAGS: 00010246
RAX: 0000000000001600 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000cc2
RBP: ffffc900006f3c18 R08: 0000000000000001 R09: 0000000000001600
R10: ffffc900006f3a40 R11: ffff88813c9fffe8 R12: 0000000000000cc2
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000cc2
FS: 00007f27ead70500(0000) GS:ffff88807ce00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000001608 CR3: 000000000582c003 CR4: 00000000001706b0
Call Trace:
pcpu_alloc_pages.constprop.0+0xe4/0x1c0
pcpu_populate_chunk+0x33/0xb0
pcpu_alloc+0x4d3/0x6f0
__alloc_percpu_gfp+0xd/0x10
alloc_mem_cgroup_per_node_info+0x54/0xb0
mem_cgroup_alloc+0xed/0x2f0
mem_cgroup_css_alloc+0x33/0x2f0
css_create+0x3a/0x1f0
cgroup_apply_control_enable+0x12b/0x150
cgroup_mkdir+0xdd/0x110
kernfs_iop_mkdir+0x4f/0x80
vfs_mkdir+0x178/0x230
do_mkdirat+0xfd/0x120
__x64_sys_mkdir+0x47/0x70
? syscall_exit_to_user_mode+0x21/0x50
do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae

Node can be in one of the following states:
1. not present (nid == NUMA_NO_NODE)
2. present, but offline (nid > NUMA_NO_NODE, node_online(nid) == 0,
NODE_DATA(nid) == NULL)
3. present and online (nid > NUMA_NO_NODE, node_online(nid) > 0,
NODE_DATA(nid) != NULL)

alloc_page_{bulk_array}node() functions verify for nid validity only
and do not check if nid is online. Enhanced verification check allows
to handle page allocation when node is in 2nd state.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
---
include/linux/gfp.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 55b2ec1f9..34a5a7def 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -551,7 +551,8 @@ alloc_pages_bulk_array(gfp_t gfp, unsigned long nr_pages, struct page **page_arr
static inline unsigned long
alloc_pages_bulk_array_node(gfp_t gfp, int nid, unsigned long nr_pages, struct page **page_array)
{
- if (nid == NUMA_NO_NODE)
+ if (nid == NUMA_NO_NODE || (!node_online(nid) &&
+ !(gfp & __GFP_THISNODE)))
nid = numa_mem_id();

return __alloc_pages_bulk(gfp, nid, NULL, nr_pages, NULL, page_array);
@@ -578,7 +579,8 @@ __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
unsigned int order)
{
- if (nid == NUMA_NO_NODE)
+ if (nid == NUMA_NO_NODE || (!node_online(nid) &&
+ !(gfp_mask & __GFP_THISNODE)))
nid = numa_mem_id();

return __alloc_pages_node(nid, gfp_mask, order);
--
2.30.0