BUG: unable to handle kernel NULL pointer dereference in setup_kmem_cache_node

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 903b77c63167 Merge tag 'linux-kselftest-4.21-rc1' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=133428e3400000
kernel config: https://syzkaller.appspot.com/x/.config?x=53a2f2aa0b1f7606
dashboard link: https://syzkaller.appspot.com/bug?extid=d6ed4ec679652b4fd4e4
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d6ed4e...@syzkaller.appspotmail.com

BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
#PF error: [WRITE]
PGD 8b2a5067 P4D 8b2a5067 PUD a53ed067 PMD 0
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 16188 Comm: syz-executor4 Not tainted 4.20.0+ #174
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:init_arraycache mm/slab.c:562 [inline]
RIP: 0010:__alloc_alien_cache mm/slab.c:669 [inline]
RIP: 0010:alloc_alien_cache mm/slab.c:689 [inline]
RIP: 0010:setup_kmem_cache_node+0x1ed/0x400 mm/slab.c:910
Code: 63 48 63 c3 48 0f a3 05 59 9c 72 08 73 56 8b 75 b8 4d 8d 2c c6 44 89
e2 48 8b 7d a8 e8 fc e9 ff ff 48 83 f8 c8 49 89 c7 74 17 <c7> 40 38 00 00
00 00 8b 45 b0 41 89 47 3c b8 0d f0 ad ba 49 89 47
RSP: 0018:ffff88804e827318 EFLAGS: 00010213
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 00000000006000c0
RDX: 00000000000000a8 RSI: 0000000000000000 RDI: ffff88812c3f0040
RBP: ffff88804e827378 R08: ffff888054cc86c0 R09: ffffed1015ce5b8f
R10: ffffed1015ce5b8f R11: ffff8880ae72dc7b R12: 0000000000000000
R13: ffff888095642648 R14: ffff888095642640 R15: 0000000000000000
FS: 00007f6fef838700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000038 CR3: 000000005034d000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
setup_kmem_cache_nodes mm/slab.c:3819 [inline]
__do_tune_cpucache+0x165/0x220 mm/slab.c:3889
do_tune_cpucache+0x25/0xd0 mm/slab.c:3898
enable_cpucache+0x3e/0xd0 mm/slab.c:3979
setup_cpu_cache+0xd4/0x1e0 mm/slab.c:1821
__kmem_cache_create+0x191/0x230 mm/slab.c:2134
create_cache+0xcd/0x1f0 mm/slab_common.c:391
kmem_cache_create_usercopy+0x18a/0x240 mm/slab_common.c:487
p9_client_create+0x986/0x1674 net/9p/client.c:1054
v9fs_session_init+0x217/0x1bb0 fs/9p/v9fs.c:421
v9fs_mount+0x7c/0x8f0 fs/9p/vfs_super.c:135
mount_fs+0xae/0x31d fs/super.c:1261
kobject: 'loop1' (000000003afcedd0): kobject_uevent_env
vfs_kern_mount.part.35+0xdc/0x4f0 fs/namespace.c:961
kobject: 'loop1' (000000003afcedd0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2469 [inline]
do_mount+0x581/0x31f0 fs/namespace.c:2801
kobject: 'loop2' (00000000108c69f3): kobject_uevent_env
kobject: 'loop2' (00000000108c69f3): fill_kobj_path: path
= '/devices/virtual/block/loop2'
ksys_mount+0x12d/0x140 fs/namespace.c:3017
__do_sys_mount fs/namespace.c:3031 [inline]
__se_sys_mount fs/namespace.c:3028 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3028
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4579b9
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6fef837c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f6fef837c90 RCX: 00000000004579b9
RDX: 0000000020000000 RSI: 00000000200000c0 RDI: 0000000000000000
RBP: 000000000073bf00 R08: 0000000020000240 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6fef8386d4
R13: 00000000004c369b R14: 00000000004d61f8 R15: 0000000000000005
Modules linked in:
CR2: 0000000000000038
---[ end trace c630b12329ae5f74 ]---
RIP: 0010:init_arraycache mm/slab.c:562 [inline]
RIP: 0010:__alloc_alien_cache mm/slab.c:669 [inline]
RIP: 0010:alloc_alien_cache mm/slab.c:689 [inline]
RIP: 0010:setup_kmem_cache_node+0x1ed/0x400 mm/slab.c:910
kobject: 'loop3' (00000000e06f18ba): kobject_uevent_env
Code: 63 48 63 c3 48 0f a3 05 59 9c 72 08 73 56 8b 75 b8 4d 8d 2c c6 44 89
e2 48 8b 7d a8 e8 fc e9 ff ff 48 83 f8 c8 49 89 c7 74 17 <c7> 40 38 00 00
00 00 8b 45 b0 41 89 47 3c b8 0d f0 ad ba 49 89 47
kobject: 'loop3' (00000000e06f18ba): fill_kobj_path: path
= '/devices/virtual/block/loop3'
RSP: 0018:ffff88804e827318 EFLAGS: 00010213
kobject: 'loop5' (00000000bc6ae381): kobject_uevent_env
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 00000000006000c0
kobject: 'loop5' (00000000bc6ae381): fill_kobj_path: path
= '/devices/virtual/block/loop5'
RDX: 00000000000000a8 RSI: 0000000000000000 RDI: ffff88812c3f0040
kobject: 'loop3' (00000000e06f18ba): kobject_uevent_env
kobject: 'loop3' (00000000e06f18ba): fill_kobj_path: path
= '/devices/virtual/block/loop3'
RBP: ffff88804e827378 R08: ffff888054cc86c0 R09: ffffed1015ce5b8f
kobject: 'loop1' (000000003afcedd0): kobject_uevent_env
R10: ffffed1015ce5b8f R11: ffff8880ae72dc7b R12: 0000000000000000
kobject: 'loop1' (000000003afcedd0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
R13: ffff888095642648 R14: ffff888095642640 R15: 0000000000000000
FS: 00007f6fef838700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000400200 CR3: 000000005034d000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[Dmitry Vyukov]

On Wed, Jan 2, 2019 at 12:36 PM syzbot
<syzbot+d6ed4e...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 903b77c63167 Merge tag 'linux-kselftest-4.21-rc1' of git:/..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=133428e3400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=53a2f2aa0b1f7606
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6ed4ec679652b4fd4e4
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+d6ed4e...@syzkaller.appspotmail.com

+mm maintianers

Am I missing something or __alloc_alien_cache misses check for
kmalloc_node result?

static struct alien_cache *__alloc_alien_cache(int node, int entries,
int batch, gfp_t gfp)
{
size_t memsize = sizeof(void *) * entries + sizeof(struct alien_cache);
struct alien_cache *alc = NULL;

alc = kmalloc_node(memsize, gfp, node);
init_arraycache(&alc->ac, entries, batch);
spin_lock_init(&alc->lock);
return alc;

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> For more options, visit https://groups.google.com/d/optout.

[Christopher Lameter]

On Wed, 2 Jan 2019, Dmitry Vyukov wrote:

> Am I missing something or __alloc_alien_cache misses check for
> kmalloc_node result?
>
> static struct alien_cache *__alloc_alien_cache(int node, int entries,
> int batch, gfp_t gfp)
> {
> size_t memsize = sizeof(void *) * entries + sizeof(struct alien_cache);
> struct alien_cache *alc = NULL;
>
> alc = kmalloc_node(memsize, gfp, node);
> init_arraycache(&alc->ac, entries, batch);
> spin_lock_init(&alc->lock);
> return alc;
> }
>

True _alloc_alien_cache() needs to check for NULL


From: Christoph Lameter <c...@linux.com>
Subject: slab: Alien caches must not be initialized if the allocation of the alien cache failed

Callers of __alloc_alien() check for NULL.
We must do the same check in __alloc_alien_cache to avoid NULL pointer dereferences
on allocation failures.

Signed-off-by: Christoph Lameter <c...@linux.com>


Index: linux/mm/slab.c
===================================================================
--- linux.orig/mm/slab.c
+++ linux/mm/slab.c
@@ -666,8 +666,10 @@ static struct alien_cache *__alloc_alien

struct alien_cache *alc = NULL;

alc = kmalloc_node(memsize, gfp, node);

- init_arraycache(&alc->ac, entries, batch);
- spin_lock_init(&alc->lock);
+ if (alc) {
+ init_arraycache(&alc->ac, entries, batch);
+ spin_lock_init(&alc->lock);
+ }
return alc;
}

[Dmitry Vyukov]

On Wed, Jan 2, 2019 at 4:51 PM Christopher Lameter <c...@linux.com> wrote:
>
> On Wed, 2 Jan 2019, Dmitry Vyukov wrote:
>
> > Am I missing something or __alloc_alien_cache misses check for
> > kmalloc_node result?
> >
> > static struct alien_cache *__alloc_alien_cache(int node, int entries,
> > int batch, gfp_t gfp)
> > {
> > size_t memsize = sizeof(void *) * entries + sizeof(struct alien_cache);
> > struct alien_cache *alc = NULL;
> >
> > alc = kmalloc_node(memsize, gfp, node);
> > init_arraycache(&alc->ac, entries, batch);
> > spin_lock_init(&alc->lock);
> > return alc;
> > }
> >
>
>
> True _alloc_alien_cache() needs to check for NULL
>
>
> From: Christoph Lameter <c...@linux.com>
> Subject: slab: Alien caches must not be initialized if the allocation of the alien cache failed
>
> Callers of __alloc_alien() check for NULL.
> We must do the same check in __alloc_alien_cache to avoid NULL pointer dereferences
> on allocation failures.
>
> Signed-off-by: Christoph Lameter <c...@linux.com>

Please add:
Reported-by: syzbot+d6ed4e...@syzkaller.appspotmail.com