Re: [d-kernel] [PATCH all] kiosk: fix incorrect KIOSK_MAX_ATTR value

[Vitaly Chikunov <vt@altlinux.org>]

On Mon, Apr 15, 2024 at 07:28:52PM +0300, kovalev@altlinux.org wrote:
> From: Vasiliy Kovalev <kovalev@altlinux.org>
> 
> The KIOSK_MAX_ATTR value should correspond to the index of the last
> available member of the structure, not their total number.
> 
> Found by Syzkaller:
> 
> [   52.512896] ===================================================
> [   52.512907] BUG: KASAN: global-out-of-bounds in
> 		__nla_validate_parse+0x2317/0x2560
> [   52.512921] Read of size 1 at addr ffffffff85205b90 by task
> 		global_out_boun/3776
> 
> [   52.512932] CPU: 0 PID: 3776 Comm: global_out_boun Not tainted
> 		6.1.81-std-def-alt1.kasan #1
> [   52.512940] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> 		BIOS 1.16.0-alt1 04/01/2014
> [   52.512945] Call Trace:
> [   52.512951]  <TASK>
> [   52.512954]  dump_stack_lvl+0x14f/0x1be
> [   52.512969]  print_report+0x171/0x47b
> [   52.512980]  ? __virt_addr_valid+0x60/0x560
> [   52.512992]  ? __nla_validate_parse+0x2317/0x2560
> [   52.512999]  kasan_report+0xbb/0x160
> [   52.513011]  ? __nla_validate_parse+0x2317/0x2560
> [   52.513020]  __nla_validate_parse+0x2317/0x2560
> [   52.513031]  ? nla_get_range_signed+0x520/0x520
> [   52.513040]  __nla_parse+0x3e/0x50
> [   52.513048]  genl_family_rcv_msg_attrs_parse.constprop.0+0x1b5/0x290
> [   52.513061]  genl_family_rcv_msg_doit+0xdf/0x330
> [   52.513070]  ? genl_family_rcv_msg_attrs_parse.constprop.0+0x290/0x290
> [   52.513078]  ? mutex_lock_io_nested+0x1650/0x1650
> [   52.513088]  ? __lock_acquire+0x15c1/0x5530
> [   52.513098]  ? cap_capable+0x1dc/0x270
> [   52.513106]  ? safesetid_security_capable+0xe3/0x170
> [   52.513116]  ? bpf_lsm_capable+0xa/0x20
> [   52.513125]  ? security_capable+0x9a/0xd0
> [   52.513132]  ? ns_capable+0xe7/0x110
> [   52.513140]  genl_rcv_msg+0x446/0x780
> [   52.513148]  ? genl_start+0x670/0x670
> [   52.513155]  ? kiosk_nl_send_msg.constprop.0+0x2f0/0x2f0
> [   52.513163]  ? lock_release+0x7a0/0x7a0
> [   52.513170]  ? netlink_deliver_tap+0x10d/0xcd0
> [   52.513178]  netlink_rcv_skb+0x14d/0x440
> [   52.513185]  ? genl_start+0x670/0x670
> [   52.513193]  ? netlink_ack+0x1340/0x1340
> [   52.513205]  ? netlink_deliver_tap+0x1a6/0xcd0
> [   52.513215]  genl_rcv+0x29/0x40
> [   52.513221]  netlink_unicast+0x550/0x810
> [   52.513241]  ? netlink_attachskb+0x8a0/0x8a0
> [   52.513248]  ? __check_object_size+0x2f8/0x650
> [   52.513258]  netlink_sendmsg+0x924/0xe20
> [   52.513266]  ? netlink_unicast+0x810/0x810
> [   52.513274]  ? bpf_lsm_socket_sendmsg+0xa/0x20
> [   52.513282]  ? netlink_unicast+0x810/0x810
> [   52.513289]  __sock_sendmsg+0x157/0x190
> [   52.513300]  ____sys_sendmsg+0x75f/0x950
> [   52.513307]  ? copy_msghdr_from_user+0x101/0x160
> [   52.513314]  ? kernel_sendmsg+0x50/0x50
> [   52.513323]  ? lock_chain_count+0x20/0x20
> [   52.513330]  ? lock_acquire+0x1fb/0x580
> [   52.513338]  ___sys_sendmsg+0x115/0x1b0
> [   52.513344]  ? __ia32_sys_recvmmsg+0x270/0x270
> [   52.513352]  ? __lock_acquire+0x15c1/0x5530
> [   52.513363]  ? lockdep_hardirqs_on_prepare+0x410/0x410
> [   52.513372]  ? __fget_light+0x217/0x280
> [   52.513381]  __sys_sendmsg+0xf8/0x1d0
> [   52.513387]  ? __sys_sendmsg_sock+0x40/0x40
> [   52.513393]  ? lock_downgrade+0x820/0x820
> [   52.513403]  ? syscall_enter_from_user_mode+0x21/0x90
> [   52.513411]  ? lockdep_hardirqs_on_prepare+0x239/0x410
> [   52.513421]  ? trace_hardirqs_on+0x2d/0x110
> [   52.513423]  do_syscall_64+0x59/0x90
> [   52.513423]  ? __ct_user_enter+0xe1/0x160
> [   52.513423]  ? exc_page_fault+0x109/0x1f0
> [   52.513423]  entry_SYSCALL_64_after_hwframe+0x64/0xce
> [   52.513423] RIP: 0033:0x7fdbe798ad49
> [   52.513423] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 8b 0d ef 70 0d 00 f7
> 		d8 64 89 01 48
> [   52.513423] RSP: 002b:00007ffef36c9aa8 EFLAGS: 00000292
> 		ORIG_RAX:000000000000002e
> [   52.513423] RAX: ffffffffffffffda RBX: 00000000200007d6 RCX: 00007fdbe798ad49
> [   52.513423] RDX: 0000000000000000 RSI: 0000000020000600 RDI: 0000000000000003
> [   52.513423] RBP: 00007ffef36c9ad0 R08: 00007ffef36c9aa7 R09: 0000000000000000
> [   52.513423] R10: 0000000000000000 R11: 0000000000000292 R12: 000055a5c5352060
> [   52.513423] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> [   52.513423]  </TASK>
> 
> [   52.513423] The buggy address belongs to the variable:
> [   52.513423]  kiosk_policy+0x30/0x60
> 
> [   52.513423] The buggy address belongs to the physical page:
> [   52.513423] page:000000009fbf94f1 refcount:1 mapcount:0
> 		mapping:0000000000000000 index:0x0 pfn:0x5205
> [   52.513423] flags: 0x1fffff80001000(reserved|node=0|zone=1|lastcpupid=0x1fffff)
> [   52.513423] raw: 001fffff80001000 ffffea0000148148 ffffea0000148148
> 		0000000000000000
> [   52.513423] raw: 0000000000000000 0000000000000000 00000001ffffffff
> 		0000000000000000
> [   52.513423] page dumped because: kasan: bad access detected
> 
> [   52.513423] Memory state around the buggy address:
> [   52.513423]  ffffffff85205a80: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9
> [   52.513423]  ffffffff85205b00: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
> [   52.513423] >ffffffff85205b80: 00 00 f9 f9 f9 f9 f9 f9 00 00 f9 f9 f9 f9 f9 f9
> [   52.513423]                          ^
> [   52.513423]  ffffffff85205c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [   52.513423]  ffffffff85205c80: 00 00 00 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
> [   52.513423] ==================================================================
> 
> Fixes: 35d97fb708d5 ("kiosk: Implement kiosk module")
> Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>

Applied, thanks

> ---
>  security/kiosk/kiosk_lsm.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/security/kiosk/kiosk_lsm.c b/security/kiosk/kiosk_lsm.c
> index cf7a7df6599582..ffd0ca3a8867d6 100644
> --- a/security/kiosk/kiosk_lsm.c
> +++ b/security/kiosk/kiosk_lsm.c
> @@ -62,10 +62,11 @@ enum kiosk_attrs {
>  	KIOSK_NOATTR = 0,
>  	KIOSK_ACTION,
>  	KIOSK_DATA,
> -	KIOSK_MAX_ATTR,
> +	__KIOSK_MAX_ATTR,
> +	KIOSK_MAX_ATTR = __KIOSK_MAX_ATTR - 1,
>  };
>  
> -static struct nla_policy kiosk_policy[KIOSK_MAX_ATTR] = {
> +static struct nla_policy kiosk_policy[KIOSK_MAX_ATTR + 1] = {
>  	[KIOSK_ACTION] = {
>  		.type = NLA_S16,
>  	},
> -- 
> 2.33.8
> 
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