[PATCH v3] net: xfrm: Fix xfrm_address_filter OOB read

From: Lin Ma
Date: Mon Jun 26 2023 - 23:39:03 EST

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We found below OOB crash:

[ 44.211730] ==================================================================
[ 44.212045] BUG: KASAN: slab-out-of-bounds in memcmp+0x8b/0xb0
[ 44.212045] Read of size 8 at addr ffff88800870f320 by task poc.xfrm/97
[ 44.212045]
[ 44.212045] CPU: 0 PID: 97 Comm: poc.xfrm Not tainted 6.4.0-rc7-00072-gdad9774deaf1-dirty #4
[ 44.212045] Call Trace:
[ 44.212045] <TASK>
[ 44.212045] dump_stack_lvl+0x37/0x50
[ 44.212045] print_report+0xcc/0x620
[ 44.212045] ? __virt_addr_valid+0xf3/0x170
[ 44.212045] ? memcmp+0x8b/0xb0
[ 44.212045] kasan_report+0xb2/0xe0
[ 44.212045] ? memcmp+0x8b/0xb0
[ 44.212045] kasan_check_range+0x39/0x1c0
[ 44.212045] memcmp+0x8b/0xb0
[ 44.212045] xfrm_state_walk+0x21c/0x420
[ 44.212045] ? __pfx_dump_one_state+0x10/0x10
[ 44.212045] xfrm_dump_sa+0x1e2/0x290
[ 44.212045] ? __pfx_xfrm_dump_sa+0x10/0x10
[ 44.212045] ? __kernel_text_address+0xd/0x40
[ 44.212045] ? kasan_unpoison+0x27/0x60
[ 44.212045] ? mutex_lock+0x60/0xe0
[ 44.212045] ? __pfx_mutex_lock+0x10/0x10
[ 44.212045] ? kasan_save_stack+0x22/0x50
[ 44.212045] netlink_dump+0x322/0x6c0
[ 44.212045] ? __pfx_netlink_dump+0x10/0x10
[ 44.212045] ? mutex_unlock+0x7f/0xd0
[ 44.212045] ? __pfx_mutex_unlock+0x10/0x10
[ 44.212045] __netlink_dump_start+0x353/0x430
[ 44.212045] xfrm_user_rcv_msg+0x3a4/0x410
[ 44.212045] ? __pfx__raw_spin_lock_irqsave+0x10/0x10
[ 44.212045] ? __pfx_xfrm_user_rcv_msg+0x10/0x10
[ 44.212045] ? __pfx_xfrm_dump_sa+0x10/0x10
[ 44.212045] ? __pfx_xfrm_dump_sa_done+0x10/0x10
[ 44.212045] ? __stack_depot_save+0x382/0x4e0
[ 44.212045] ? filter_irq_stacks+0x1c/0x70
[ 44.212045] ? kasan_save_stack+0x32/0x50
[ 44.212045] ? kasan_save_stack+0x22/0x50
[ 44.212045] ? kasan_set_track+0x25/0x30
[ 44.212045] ? __kasan_slab_alloc+0x59/0x70
[ 44.212045] ? kmem_cache_alloc_node+0xf7/0x260
[ 44.212045] ? kmalloc_reserve+0xab/0x120
[ 44.212045] ? __alloc_skb+0xcf/0x210
[ 44.212045] ? netlink_sendmsg+0x509/0x700
[ 44.212045] ? sock_sendmsg+0xde/0xe0
[ 44.212045] ? __sys_sendto+0x18d/0x230
[ 44.212045] ? __x64_sys_sendto+0x71/0x90
[ 44.212045] ? do_syscall_64+0x3f/0x90
[ 44.212045] ? entry_SYSCALL_64_after_hwframe+0x72/0xdc
[ 44.212045] ? netlink_sendmsg+0x509/0x700
[ 44.212045] ? sock_sendmsg+0xde/0xe0
[ 44.212045] ? __sys_sendto+0x18d/0x230
[ 44.212045] ? __x64_sys_sendto+0x71/0x90
[ 44.212045] ? do_syscall_64+0x3f/0x90
[ 44.212045] ? entry_SYSCALL_64_after_hwframe+0x72/0xdc
[ 44.212045] ? kasan_save_stack+0x22/0x50
[ 44.212045] ? kasan_set_track+0x25/0x30
[ 44.212045] ? kasan_save_free_info+0x2e/0x50
[ 44.212045] ? __kasan_slab_free+0x10a/0x190
[ 44.212045] ? kmem_cache_free+0x9c/0x340
[ 44.212045] ? netlink_recvmsg+0x23c/0x660
[ 44.212045] ? sock_recvmsg+0xeb/0xf0
[ 44.212045] ? __sys_recvfrom+0x13c/0x1f0
[ 44.212045] ? __x64_sys_recvfrom+0x71/0x90
[ 44.212045] ? do_syscall_64+0x3f/0x90
[ 44.212045] ? entry_SYSCALL_64_after_hwframe+0x72/0xdc
[ 44.212045] ? copyout+0x3e/0x50
[ 44.212045] netlink_rcv_skb+0xd6/0x210
[ 44.212045] ? __pfx_xfrm_user_rcv_msg+0x10/0x10
[ 44.212045] ? __pfx_netlink_rcv_skb+0x10/0x10
[ 44.212045] ? __pfx_sock_has_perm+0x10/0x10
[ 44.212045] ? mutex_lock+0x8d/0xe0
[ 44.212045] ? __pfx_mutex_lock+0x10/0x10
[ 44.212045] xfrm_netlink_rcv+0x44/0x50
[ 44.212045] netlink_unicast+0x36f/0x4c0
[ 44.212045] ? __pfx_netlink_unicast+0x10/0x10
[ 44.212045] ? netlink_recvmsg+0x500/0x660
[ 44.212045] netlink_sendmsg+0x3b7/0x700
[ 44.212045] ? __pfx_netlink_sendmsg+0x10/0x10
[ 44.212045] ? __pfx_netlink_sendmsg+0x10/0x10
[ 44.212045] sock_sendmsg+0xde/0xe0
[ 44.212045] __sys_sendto+0x18d/0x230
[ 44.212045] ? __pfx___sys_sendto+0x10/0x10
[ 44.212045] ? rcu_core+0x44a/0xe10
[ 44.212045] ? __rseq_handle_notify_resume+0x45b/0x740
[ 44.212045] ? _raw_spin_lock_irq+0x81/0xe0
[ 44.212045] ? __pfx___rseq_handle_notify_resume+0x10/0x10
[ 44.212045] ? __pfx_restore_fpregs_from_fpstate+0x10/0x10
[ 44.212045] ? __pfx_blkcg_maybe_throttle_current+0x10/0x10
[ 44.212045] ? __pfx_task_work_run+0x10/0x10
[ 44.212045] __x64_sys_sendto+0x71/0x90
[ 44.212045] do_syscall_64+0x3f/0x90
[ 44.212045] entry_SYSCALL_64_after_hwframe+0x72/0xdc
[ 44.212045] RIP: 0033:0x44b7da
[ 44.212045] RSP: 002b:00007ffdc8838548 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
[ 44.212045] RAX: ffffffffffffffda RBX: 00007ffdc8839978 RCX: 000000000044b7da
[ 44.212045] RDX: 0000000000000038 RSI: 00007ffdc8838770 RDI: 0000000000000003
[ 44.212045] RBP: 00007ffdc88385b0 R08: 00007ffdc883858c R09: 000000000000000c
[ 44.212045] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
[ 44.212045] R13: 00007ffdc8839968 R14: 00000000004c37d0 R15: 0000000000000001
[ 44.212045] </TASK>
[ 44.212045]
[ 44.212045] Allocated by task 97:
[ 44.212045] kasan_save_stack+0x22/0x50
[ 44.212045] kasan_set_track+0x25/0x30
[ 44.212045] __kasan_kmalloc+0x7f/0x90
[ 44.212045] __kmalloc_node_track_caller+0x5b/0x140
[ 44.212045] kmemdup+0x21/0x50
[ 44.212045] xfrm_dump_sa+0x17d/0x290
[ 44.212045] netlink_dump+0x322/0x6c0
[ 44.212045] __netlink_dump_start+0x353/0x430
[ 44.212045] xfrm_user_rcv_msg+0x3a4/0x410
[ 44.212045] netlink_rcv_skb+0xd6/0x210
[ 44.212045] xfrm_netlink_rcv+0x44/0x50
[ 44.212045] netlink_unicast+0x36f/0x4c0
[ 44.212045] netlink_sendmsg+0x3b7/0x700
[ 44.212045] sock_sendmsg+0xde/0xe0
[ 44.212045] __sys_sendto+0x18d/0x230
[ 44.212045] __x64_sys_sendto+0x71/0x90
[ 44.212045] do_syscall_64+0x3f/0x90
[ 44.212045] entry_SYSCALL_64_after_hwframe+0x72/0xdc
[ 44.212045]
[ 44.212045] The buggy address belongs to the object at ffff88800870f300
[ 44.212045] which belongs to the cache kmalloc-64 of size 64
[ 44.212045] The buggy address is located 32 bytes inside of
[ 44.212045] allocated 36-byte region [ffff88800870f300, ffff88800870f324)
[ 44.212045]
[ 44.212045] The buggy address belongs to the physical page:
[ 44.212045] page:00000000e4de16ee refcount:1 mapcount:0 mapping:000000000 ...
[ 44.212045] flags: 0x100000000000200(slab|node=0|zone=1)
[ 44.212045] page_type: 0xffffffff()
[ 44.212045] raw: 0100000000000200 ffff888004c41640 dead000000000122 0000000000000000
[ 44.212045] raw: 0000000000000000 0000000080200020 00000001ffffffff 0000000000000000
[ 44.212045] page dumped because: kasan: bad access detected
[ 44.212045]
[ 44.212045] Memory state around the buggy address:
[ 44.212045] ffff88800870f200: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 44.212045] ffff88800870f280: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
[ 44.212045] >ffff88800870f300: 00 00 00 00 04 fc fc fc fc fc fc fc fc fc fc fc
[ 44.212045] ^
[ 44.212045] ffff88800870f380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 44.212045] ffff88800870f400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 44.212045] ==================================================================

By investigating the code, we find the root cause of this OOB is the lack
of checks in xfrm_dump_sa(). The buggy code allows a malicious user to pass
arbitrary value of filter->splen/dplen. Hence, with crafted xfrm states,
the attacker can achieve 8 bytes heap OOB read, which causes info leak.

if (attrs[XFRMA_ADDRESS_FILTER]) {
filter = kmemdup(nla_data(attrs[XFRMA_ADDRESS_FILTER]),
sizeof(*filter), GFP_KERNEL);
if (filter == NULL)
return -ENOMEM;
// NO MORE CHECKS HERE !!!
}

This patch fixes the OOB by adding necessary boundary checks, just like
the code in pfkey_dump() function.

Fixes: d3623099d350 ("ipsec: add support of limited SA dump")
Signed-off-by: Lin Ma <linma@xxxxxxxxxx>
---
V1 -> V2: add kfree() hence no memory leak
V2 -> V3: add additional note and use > instead of >= to
allow complete filter comparision

net/xfrm/xfrm_user.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index c34a2a06ca94..7c91deadc36e 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1267,6 +1267,15 @@ static int xfrm_dump_sa(struct sk_buff *skb, struct netlink_callback *cb)
sizeof(*filter), GFP_KERNEL);
if (filter == NULL)
return -ENOMEM;
+
+ /* see addr_match(), (prefix length >> 5) << 2
+ * will be used to compare xfrm_address_t
+ */
+ if (filter->splen > (sizeof(xfrm_address_t) << 3) ||
+ filter->dplen > (sizeof(xfrm_address_t) << 3)) {
+ kfree(filter);
+ return -EINVAL;
+ }
}

if (attrs[XFRMA_PROTO])
--
2.17.1

Next message: Yang, Weijiang: "Re: [PATCH v3 13/21] KVM:VMX: Emulate reads and writes to CET MSRs"
Previous message: Matthieu Baerts: "Re: [PATCH net-next] perf trace: fix MSG_SPLICE_PAGES build error"
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