[syzbot] [net?] KASAN: slab-out-of-bounds Read in dsa_user_changeupper

[syzbot] [net?] KASAN: slab-out-of-bounds Read in dsa_user_changeupper

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9fb3dc1e9af2 Merge branch 'phy-listing-link_topology-track..
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11269ba5e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a4e9ca8e3c104d2a
dashboard link: https://syzkaller.appspot.com/bug?extid=d81bcd883824180500c8
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1267ba7ee80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=151ed731e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/08a6d58357f2/disk-9fb3dc1e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/390509d5ee5f/vmlinux-9fb3dc1e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d7efcbce1f12/bzImage-9fb3dc1e.xz

The issue was bisected to:

commit 43a71cd66b9c0a4af3d15d8644359fde35bdbed0
Author: Coco Li <lixiaoyan@google.com>
Date:   Mon Dec 4 20:12:30 2023 +0000

    net-device: reorganize net_device fast path variables

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17832409e80000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=14432409e80000
console output: https://syzkaller.appspot.com/x/log.txt?x=10432409e80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d81bcd883824180500c8@syzkaller.appspotmail.com
Fixes: 43a71cd66b9c ("net-device: reorganize net_device fast path variables")

==================================================================
BUG: KASAN: slab-out-of-bounds in dsa_user_to_port net/dsa/user.h:58 [inline]
BUG: KASAN: slab-out-of-bounds in dsa_user_changeupper+0x61a/0x6e0 net/dsa/user.c:2809
Read of size 8 at addr ffff888015ebecf0 by task syz-executor278/5066

CPU: 1 PID: 5066 Comm: syz-executor278 Not tainted 6.7.0-rc6-syzkaller-01740-g9fb3dc1e9af2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xc4/0x620 mm/kasan/report.c:475
 kasan_report+0xda/0x110 mm/kasan/report.c:588
 dsa_user_to_port net/dsa/user.h:58 [inline]
 dsa_user_changeupper+0x61a/0x6e0 net/dsa/user.c:2809
 dsa_user_netdevice_event+0xd04/0x3480 net/dsa/user.c:3345
 notifier_call_chain+0xb6/0x3b0 kernel/notifier.c:93
 call_netdevice_notifiers_info+0xbe/0x130 net/core/dev.c:1967
 __netdev_upper_dev_link+0x439/0x850 net/core/dev.c:7760
 netdev_upper_dev_link+0x92/0xc0 net/core/dev.c:7801
 register_vlan_dev+0x396/0x940 net/8021q/vlan.c:183
 register_vlan_device net/8021q/vlan.c:277 [inline]
 vlan_ioctl_handler+0x8dd/0xa70 net/8021q/vlan.c:621
 sock_ioctl+0x4bd/0x6b0 net/socket.c:1303
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl fs/ioctl.c:857 [inline]
 __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f0a94e172e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeda224968 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffeda224b38 RCX: 00007f0a94e172e9
RDX: 0000000020000380 RSI: 0000000000008982 RDI: 0000000000000003
RBP: 00007f0a94e8a610 R08: 0000000000000000 R09: 00007ffeda224b38
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffeda224b28 R14: 0000000000000001 R15: 0000000000000001
 </TASK>

Allocated by task 1:
 kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node+0x5c/0x90 mm/slab_common.c:1014
 kmalloc_node include/linux/slab.h:620 [inline]
 kvmalloc_node+0x99/0x1a0 mm/util.c:617
 kvmalloc include/linux/slab.h:738 [inline]
 kvzalloc include/linux/slab.h:746 [inline]
 alloc_netdev_mqs+0xb3/0x1360 net/core/dev.c:10827
 dummy_init_one drivers/net/dummy.c:158 [inline]
 dummy_init_module+0xcf/0x1b0 drivers/net/dummy.c:184
 do_one_initcall+0x11c/0x650 init/main.c:1236
 do_initcall_level init/main.c:1298 [inline]
 do_initcalls init/main.c:1314 [inline]
 do_basic_setup init/main.c:1333 [inline]
 kernel_init_freeable+0x687/0xc10 init/main.c:1551
 kernel_init+0x1c/0x2a0 init/main.c:1441
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

The buggy address belongs to the object at ffff888015ebe000
 which belongs to the cache kmalloc-cg-4k of size 4096
The buggy address is located 3312 bytes inside of
 allocated 3319-byte region [ffff888015ebe000, ffff888015ebecf7)

The buggy address belongs to the physical page:
page:ffffea000057ae00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x15eb8
head:ffffea000057ae00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff88801304f500 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd60c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 4608693968, free_ts 0
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x2d0/0x350 mm/page_alloc.c:1544
 prep_new_page mm/page_alloc.c:1551 [inline]
 get_page_from_freelist+0xa28/0x3730 mm/page_alloc.c:3319
 __alloc_pages+0x22e/0x2420 mm/page_alloc.c:4575
 alloc_pages_mpol+0x258/0x5f0 mm/mempolicy.c:2133
 alloc_slab_page mm/slub.c:1870 [inline]
 allocate_slab mm/slub.c:2017 [inline]
 new_slab+0x283/0x3c0 mm/slub.c:2070
 ___slab_alloc+0x979/0x1500 mm/slub.c:3223
 __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3322
 __slab_alloc_node mm/slub.c:3375 [inline]
 slab_alloc_node mm/slub.c:3468 [inline]
 __kmem_cache_alloc_node+0x131/0x310 mm/slub.c:3517
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node+0x4c/0x90 mm/slab_common.c:1014
 kmalloc_node include/linux/slab.h:620 [inline]
 kvmalloc_node+0x99/0x1a0 mm/util.c:617
 kvmalloc include/linux/slab.h:738 [inline]
 kvzalloc include/linux/slab.h:746 [inline]
 alloc_netdev_mqs+0xb3/0x1360 net/core/dev.c:10827
 loopback_net_init+0x38/0x170 drivers/net/loopback.c:214
 ops_init+0xb9/0x650 net/core/net_namespace.c:136
 __register_pernet_operations net/core/net_namespace.c:1214 [inline]
 register_pernet_operations+0x34b/0x820 net/core/net_namespace.c:1283
 register_pernet_device+0x29/0x70 net/core/net_namespace.c:1370
 net_dev_init+0x7b1/0xaa0 net/core/dev.c:11747
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888015ebeb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888015ebec00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888015ebec80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 07 fc
                                                             ^
 ffff888015ebed00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888015ebed80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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If you want to overwrite report's subsystems, reply with:
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#syz undup

Re: [syzbot] [net?] KASAN: slab-out-of-bounds Read in dsa_user_changeupper

[Vladimir Oltean]

[-- Attachment #1: Type: text/plain, Size: 1448 bytes --]

On Tue, Jan 09, 2024 at 10:17:34AM -0800, syzbot wrote:
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in dsa_user_to_port net/dsa/user.h:58 [inline]
> BUG: KASAN: slab-out-of-bounds in dsa_user_changeupper+0x61a/0x6e0 net/dsa/user.c:2809
> Read of size 8 at addr ffff888015ebecf0 by task syz-executor278/5066
> 
> CPU: 1 PID: 5066 Comm: syz-executor278 Not tainted 6.7.0-rc6-syzkaller-01740-g9fb3dc1e9af2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
>  print_address_description mm/kasan/report.c:364 [inline]
>  print_report+0xc4/0x620 mm/kasan/report.c:475
>  kasan_report+0xda/0x110 mm/kasan/report.c:588
>  dsa_user_to_port net/dsa/user.h:58 [inline]
>  dsa_user_changeupper+0x61a/0x6e0 net/dsa/user.c:2809
>  dsa_user_netdevice_event+0xd04/0x3480 net/dsa/user.c:3345
>  notifier_call_chain+0xb6/0x3b0 kernel/notifier.c:93
>  call_netdevice_notifiers_info+0xbe/0x130 net/core/dev.c:1967
>  __netdev_upper_dev_link+0x439/0x850 net/core/dev.c:7760
>  netdev_upper_dev_link+0x92/0xc0 net/core/dev.c:7801
>  register_vlan_dev+0x396/0x940 net/8021q/vlan.c:183
>  register_vlan_device net/8021q/vlan.c:277 [inline]
>  vlan_ioctl_handler+0x8dd/0xa70 net/8021q/vlan.c:621
>  sock_ioctl+0x4bd/0x6b0 net/socket.c:1303

#syz test

[-- Attachment #2: 0001-net-dsa-fix-bad-dsa_user_to_port-calls-on-non-DSA-ne.patch --]
[-- Type: text/x-diff, Size: 3195 bytes --]

From e3b8e714f152a8fbdc72d501d3839a6350be70a0 Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: Tue, 9 Jan 2024 20:51:57 +0200
Subject: [PATCH] net: dsa: fix bad dsa_user_to_port() calls on non-DSA
 netdevice events

After the blamed commit, we started doing this dereference for every
NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER in the system.

static inline struct dsa_port *dsa_user_to_port(const struct net_device *dev)
{
	struct dsa_user_priv *p = netdev_priv(dev);

	return p->dp;
}

Syzbot unfairly blames this on commit 43a71cd66b9c ("net-device:
reorganize net_device fast path variables"), which probably changed
sizeof(struct net_device), vaguely relevant below.

static inline void *netdev_priv(const struct net_device *dev)
{
	return (char *)dev + ALIGN(sizeof(struct net_device), NETDEV_ALIGN);
}

What we see now is:

BUG: KASAN: slab-out-of-bounds in dsa_user_to_port net/dsa/user.h:58 [inline]
BUG: KASAN: slab-out-of-bounds in dsa_user_changeupper+0x61a/0x6e0 net/dsa/user.c:2809
Read of size 8 at addr ffff888015ebecf0 by task syz-executor278/5066

Call Trace:
 kasan_report+0xda/0x110 mm/kasan/report.c:588
 dsa_user_to_port net/dsa/user.h:58 [inline]
 dsa_user_changeupper+0x61a/0x6e0 net/dsa/user.c:2809
 dsa_user_netdevice_event+0xd04/0x3480 net/dsa/user.c:3345
 notifier_call_chain+0xb6/0x3b0 kernel/notifier.c:93
 call_netdevice_notifiers_info+0xbe/0x130 net/core/dev.c:1967
 __netdev_upper_dev_link+0x439/0x850 net/core/dev.c:7760
 netdev_upper_dev_link+0x92/0xc0 net/core/dev.c:7801
 register_vlan_dev+0x396/0x940 net/8021q/vlan.c:183
 register_vlan_device net/8021q/vlan.c:277 [inline]
 vlan_ioctl_handler+0x8dd/0xa70 net/8021q/vlan.c:621
 sock_ioctl+0x4bd/0x6b0 net/socket.c:1303

Full analysis of why we're seeing this just now is pending.

Fixes: 4c3f80d22b2e ("net: dsa: walk through all changeupper notifier functions")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 net/dsa/user.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/dsa/user.c b/net/dsa/user.c
index b738a466e2dc..b15e71cc342c 100644
--- a/net/dsa/user.c
+++ b/net/dsa/user.c
@@ -2806,13 +2806,14 @@ EXPORT_SYMBOL_GPL(dsa_user_dev_check);
 static int dsa_user_changeupper(struct net_device *dev,
 				struct netdev_notifier_changeupper_info *info)
 {
-	struct dsa_port *dp = dsa_user_to_port(dev);
 	struct netlink_ext_ack *extack;
 	int err = NOTIFY_DONE;
+	struct dsa_port *dp;
 
 	if (!dsa_user_dev_check(dev))
 		return err;
 
+	dp = dsa_user_to_port(dev);
 	extack = netdev_notifier_info_to_extack(&info->info);
 
 	if (netif_is_bridge_master(info->upper_dev)) {
@@ -2865,11 +2866,13 @@ static int dsa_user_changeupper(struct net_device *dev,
 static int dsa_user_prechangeupper(struct net_device *dev,
 				   struct netdev_notifier_changeupper_info *info)
 {
-	struct dsa_port *dp = dsa_user_to_port(dev);
+	struct dsa_port *dp;
 
 	if (!dsa_user_dev_check(dev))
 		return NOTIFY_DONE;
 
+	dp = dsa_user_to_port(dev);
+
 	if (netif_is_bridge_master(info->upper_dev) && !info->linking)
 		dsa_port_pre_bridge_leave(dp, info->upper_dev);
 	else if (netif_is_lag_master(info->upper_dev) && !info->linking)
-- 
2.34.1

Re: [syzbot] [net?] KASAN: slab-out-of-bounds Read in dsa_user_changeupper

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+d81bcd883824180500c8@syzkaller.appspotmail.com

Tested on:

commit:         a7fe0881 Merge git://git.kernel.org/pub/scm/linux/kern..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=11f5ed75e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f71e27f13422e1cd
dashboard link: https://syzkaller.appspot.com/bug?extid=d81bcd883824180500c8
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=125c2bf3e80000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [net?] KASAN: slab-out-of-bounds Read in dsa_user_changeupper

[Vladimir Oltean]

On Tue, Jan 09, 2024 at 10:17:34AM -0800, syzbot wrote:
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title

#syz fix: net: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events