Date:   Wed, 2 Jan 2019 12:54:03 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+d6ed4ec679652b4fd4e4@...kaller.appspotmail.com>
Cc:     Dominique Martinet <asmadeus@...ewreck.org>,
        David Miller <davem@...emloft.net>,
        Eric Van Hensbergen <ericvh@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Latchesar Ionkov <lucho@...kov.net>,
        netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        v9fs-developer@...ts.sourceforge.net,
        Linux-MM <linux-mm@...ck.org>, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: BUG: unable to handle kernel NULL pointer dereference in setup_kmem_cache_node

On Wed, Jan 2, 2019 at 12:36 PM syzbot
<syzbot+d6ed4ec679652b4fd4e4@...kaller.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+d6ed4ec679652b4fd4e4@...kaller.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;
}


> 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
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
>
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