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From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date: Thu, 4 Apr 2024 14:31:02 -0400
Message-ID: <CABBYNZJB+n7NN2QkBt5heDeWq0wbyE1Y4CUyK9Ne7vBRnmuWaw@mail.gmail.com>
Subject: Re: [PATCH net] Bluetooth: validate setsockopt( BT_PKT_STATUS /
 BT_DEFER_SETUP) user input
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>, 
	Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org, eric.dumazet@gmail.com, 
	syzbot <syzkaller@googlegroups.com>, Marcel Holtmann <marcel@holtmann.org>, 
	Johan Hedberg <johan.hedberg@gmail.com>, linux-bluetooth@vger.kernel.org
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Hi Eric,

On Thu, Apr 4, 2024 at 8:36=E2=80=AFAM Eric Dumazet <edumazet@google.com> w=
rote:
>
> syzbot reported sco_sock_setsockopt() is copying data without
> checking user input length.
>
>  BUG: KASAN: slab-out-of-bounds in copy_from_sockptr_offset include/linux=
/sockptr.h:49 [inline]
>  BUG: KASAN: slab-out-of-bounds in copy_from_sockptr include/linux/sockpt=
r.h:55 [inline]
>  BUG: KASAN: slab-out-of-bounds in sco_sock_setsockopt+0xc0b/0xf90 net/bl=
uetooth/sco.c:893
> Read of size 4 at addr ffff88805f7b15a3 by task syz-executor.5/12578
>
> CPU: 1 PID: 12578 Comm: syz-executor.5 Not tainted 6.8.0-syzkaller-08951-=
gfe46a7dd189e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS G=
oogle 03/27/2024
> Call Trace:
>  <TASK>
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
>   print_address_description mm/kasan/report.c:377 [inline]
>   print_report+0x169/0x550 mm/kasan/report.c:488
>   kasan_report+0x143/0x180 mm/kasan/report.c:601
>   copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
>   copy_from_sockptr include/linux/sockptr.h:55 [inline]
>   sco_sock_setsockopt+0xc0b/0xf90 net/bluetooth/sco.c:893
>   do_sock_setsockopt+0x3b1/0x720 net/socket.c:2311
>   __sys_setsockopt+0x1ae/0x250 net/socket.c:2334
>   __do_sys_setsockopt net/socket.c:2343 [inline]
>   __se_sys_setsockopt net/socket.c:2340 [inline]
>   __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
>  do_syscall_64+0xfd/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
> RIP: 0033:0x7f3c2487dde9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f=
7 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 b0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f3c256b40c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 00007f3c249abf80 RCX: 00007f3c2487dde9
> RDX: 0000000000000010 RSI: 0000000000000112 RDI: 0000000000000008
> RBP: 00007f3c248ca47a R08: 0000000000000002 R09: 0000000000000000
> R10: 0000000020000080 R11: 0000000000000246 R12: 0000000000000000
> R13: 000000000000004d R14: 00007f3c249abf80 R15: 00007fff5dcf4978
>  </TASK>
>
> Allocated by task 12578:
>   kasan_save_stack mm/kasan/common.c:47 [inline]
>   kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
>   poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
>   __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
>   kasan_kmalloc include/linux/kasan.h:211 [inline]
>   __do_kmalloc_node mm/slub.c:3966 [inline]
>   __kmalloc+0x233/0x4a0 mm/slub.c:3979
>   kmalloc include/linux/slab.h:632 [inline]
>   __cgroup_bpf_run_filter_setsockopt+0xd2f/0x1040 kernel/bpf/cgroup.c:186=
9
>   do_sock_setsockopt+0x6b4/0x720 net/socket.c:2293
>   __sys_setsockopt+0x1ae/0x250 net/socket.c:2334
>   __do_sys_setsockopt net/socket.c:2343 [inline]
>   __se_sys_setsockopt net/socket.c:2340 [inline]
>   __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
>  do_syscall_64+0xfd/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
>
> The buggy address belongs to the object at ffff88805f7b15a0
>  which belongs to the cache kmalloc-8 of size 8
> The buggy address is located 1 bytes to the right of
>  allocated 2-byte region [ffff88805f7b15a0, ffff88805f7b15a2)
>
> The buggy address belongs to the physical page:
> page:ffffea00017dec40 refcount:1 mapcount:0 mapping:0000000000000000 inde=
x:0x0 pfn:0x5f7b1
> flags: 0xfff00000000800(slab|node=3D0|zone=3D1|lastcpupid=3D0x7ff)
> page_type: 0xffffffff()
> raw: 00fff00000000800 ffff888014c41280 ffffea0000a26d80 dead000000000002
> raw: 0000000000000000 0000000080800080 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(=
GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 5091, tgid 5091 (syz-executor.3=
), ts 75758857522, free_ts 75730585588
>   set_page_owner include/linux/page_owner.h:31 [inline]
>   post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1533
>   prep_new_page mm/page_alloc.c:1540 [inline]
>   get_page_from_freelist+0x33ea/0x3580 mm/page_alloc.c:3311
>   __alloc_pages+0x256/0x680 mm/page_alloc.c:4569
>   __alloc_pages_node include/linux/gfp.h:238 [inline]
>   alloc_pages_node include/linux/gfp.h:261 [inline]
>   alloc_slab_page+0x5f/0x160 mm/slub.c:2175
>   allocate_slab mm/slub.c:2338 [inline]
>   new_slab+0x84/0x2f0 mm/slub.c:2391
>   ___slab_alloc+0xc73/0x1260 mm/slub.c:3525
>   __slab_alloc mm/slub.c:3610 [inline]
>   __slab_alloc_node mm/slub.c:3663 [inline]
>   slab_alloc_node mm/slub.c:3835 [inline]
>   __do_kmalloc_node mm/slub.c:3965 [inline]
>   __kmalloc_node_track_caller+0x2d6/0x4e0 mm/slub.c:3986
>   kstrdup+0x3a/0x80 mm/util.c:62
>   __kernfs_new_node+0x9d/0x880 fs/kernfs/dir.c:611
>   kernfs_new_node+0x13a/0x240 fs/kernfs/dir.c:691
>   kernfs_create_dir_ns+0x43/0x120 fs/kernfs/dir.c:1052
>   sysfs_create_dir_ns+0x189/0x3a0 fs/sysfs/dir.c:59
>   create_dir lib/kobject.c:73 [inline]
>   kobject_add_internal+0x435/0x8d0 lib/kobject.c:240
>   kobject_add_varg lib/kobject.c:374 [inline]
>   kobject_init_and_add+0x124/0x190 lib/kobject.c:457
>   netdev_queue_add_kobject net/core/net-sysfs.c:1786 [inline]
>   netdev_queue_update_kobjects+0x1ee/0x5f0 net/core/net-sysfs.c:1838
>   register_queue_kobjects net/core/net-sysfs.c:1900 [inline]
>   netdev_register_kobject+0x265/0x320 net/core/net-sysfs.c:2140
> page last free pid 5103 tgid 5103 stack trace:
>   reset_page_owner include/linux/page_owner.h:24 [inline]
>   free_pages_prepare mm/page_alloc.c:1140 [inline]
>   free_unref_page_prepare+0x968/0xa90 mm/page_alloc.c:2346
>   free_unref_page_list+0x5a3/0x850 mm/page_alloc.c:2532
>   release_pages+0x2744/0x2a80 mm/swap.c:1042
>   tlb_batch_pages_flush mm/mmu_gather.c:98 [inline]
>   tlb_flush_mmu_free mm/mmu_gather.c:293 [inline]
>   tlb_flush_mmu+0x34d/0x4e0 mm/mmu_gather.c:300
>   tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:392
>   exit_mmap+0x4b6/0xd40 mm/mmap.c:3300
>   __mmput+0x115/0x3c0 kernel/fork.c:1345
>   exit_mm+0x220/0x310 kernel/exit.c:569
>   do_exit+0x99e/0x27e0 kernel/exit.c:865
>   do_group_exit+0x207/0x2c0 kernel/exit.c:1027
>   __do_sys_exit_group kernel/exit.c:1038 [inline]
>   __se_sys_exit_group kernel/exit.c:1036 [inline]
>   __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
>  do_syscall_64+0xfd/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
>
> Memory state around the buggy address:
>  ffff88805f7b1480: 05 fc fc fc 05 fc fc fc fa fc fc fc 05 fc fc fc
>  ffff88805f7b1500: 05 fc fc fc 05 fc fc fc 05 fc fc fc 05 fc fc fc
> >ffff88805f7b1580: 04 fc fc fc 02 fc fc fc fa fc fc fc 05 fc fc fc
>                                ^
>  ffff88805f7b1600: fa fc fc fc 05 fc fc fc fa fc fc fc 05 fc fc fc
>  ffff88805f7b1680: 05 fc fc fc 05 fc fc fc 00 fc fc fc fa fc fc fc
>
> Fixes: 00398e1d5183 ("Bluetooth: Add support for BT_PKT_STATUS CMSG data =
for SCO connections")
> Fixes: b96e9c671b05 ("Bluetooth: Add BT_DEFER_SETUP option to sco socket"=
)
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Marcel Holtmann <marcel@holtmann.org>
> Cc: Johan Hedberg <johan.hedberg@gmail.com>
> Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com> (supporter:BLUETOOTH SU=
BSYSTEM)
> Cc: linux-bluetooth@vger.kernel.org
> ---
>  net/bluetooth/sco.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
> index 43daf965a01e4ac5c9329150080b00dcd63c7e1c..9d013f01865fd2509f28eac3b=
ceadf682f0a5edb 100644
> --- a/net/bluetooth/sco.c
> +++ b/net/bluetooth/sco.c
> @@ -843,6 +843,10 @@ static int sco_sock_setsockopt(struct socket *sock, =
int level, int optname,
>                         break;
>                 }
>
> +               if (optlen < sizeof(u32)) {
> +                       err =3D -EINVAL;
> +                       break;
> +               }

Usually we deal with this sort of problem by doing len =3D
min_t(unsigned int, sizeof(u32), optlen) so we truncate the value if
smaller, perhaps it would be better to have a helper function that
does len check internally.

>                 if (copy_from_sockptr(&opt, optval, sizeof(u32))) {
>                         err =3D -EFAULT;
>                         break;
> @@ -890,6 +894,10 @@ static int sco_sock_setsockopt(struct socket *sock, =
int level, int optname,
>                 break;
>
>         case BT_PKT_STATUS:
> +               if (optlen < sizeof(u32)) {
> +                       err =3D -EINVAL;
> +                       break;
> +               }
>                 if (copy_from_sockptr(&opt, optval, sizeof(u32))) {
>                         err =3D -EFAULT;
>                         break;
> --
> 2.44.0.478.gd926399ef9-goog
>


--=20
Luiz Augusto von Dentz