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From: Edward Adam Davis <eadavis@qq.com>
To: syzbot+af9492708df9797198d6@syzkaller.appspotmail.com
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Subject: [PATCH] bpf: fix null ptr deref in dev_map_enqueue
Date: Sun, 31 Mar 2024 17:08:26 +0800
In-Reply-To: <00000000000069ee1a06149ff00c@google.com>
References: <00000000000069ee1a06149ff00c@google.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

[Syzbot reported]
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 5179 Comm: syz-executor120 Not tainted 6.8.0-syzkaller-05271-gf99c5f563c17 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
RIP: 0010:dev_map_enqueue+0x31/0x3e0 kernel/bpf/devmap.c:539
Code: 41 56 41 55 41 54 53 48 83 ec 18 49 89 d4 49 89 f5 48 89 fd 49 be 00 00 00 00 00 fc ff df e8 e6 45 d8 ff 48 89 e8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 ef e8 d0 8b 3b 00 4c 8b 7d 00 48 83 c5
RSP: 0018:ffffc90003b0f688 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff888025258000
RDX: 0000000000000000 RSI: ffff888024035070 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000005 R09: ffffffff894ff55e
R10: 0000000000000004 R11: ffff888025258000 R12: ffff8880157d8000
R13: ffff888024035070 R14: dffffc0000000000 R15: ffff8880b943c088
FS:  00007fd0098e46c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200009c0 CR3: 0000000025314000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __xdp_do_redirect_frame net/core/filter.c:4384 [inline]
 xdp_do_redirect_frame+0x20d/0x4d0 net/core/filter.c:4438
 xdp_test_run_batch net/bpf/test_run.c:336 [inline]
 bpf_test_run_xdp_live+0xe8a/0x1e90 net/bpf/test_run.c:384
 bpf_prog_test_run_xdp+0x813/0x11b0 net/bpf/test_run.c:1267
 bpf_prog_test_run+0x33a/0x3b0 kernel/bpf/syscall.c:4240
 __sys_bpf+0x48d/0x810 kernel/bpf/syscall.c:5649
 __do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
 do_syscall_64+0xfb/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7fd00992a0d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 18 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd0098e4238 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fd0099b43e8 RCX: 00007fd00992a0d9
RDX: 0000000000000050 RSI: 0000000020000240 RDI: 000000000000000a
RBP: 00007fd0099b43e0 R08: 00007fd0098e46c0 R09: 00007fd0098e46c0
R10: 00007fd0098e46c0 R11: 0000000000000246 R12: 00007fd009981060
R13: 0000000000000016 R14: 00007fffcb70c160 R15: 00007fffcb70c248
 </TASK>
[Fix]
On the execution path of bpf_prog_test_run(), due to ri->map being NULL, 
ri->tgtvalue was not set correctly.

Reported-and-tested-by: syzbot+af9492708df9797198d6@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 kernel/bpf/devmap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 4e2cdbb5629f..ef20de14154a 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -86,6 +86,7 @@ struct bpf_dtab {
 static DEFINE_PER_CPU(struct list_head, dev_flush_list);
 static DEFINE_SPINLOCK(dev_map_lock);
 static LIST_HEAD(dev_map_list);
+static bool is_valid_dst(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf);
 
 static struct hlist_head *dev_map_create_hash(unsigned int entries,
 					      int numa_node)
@@ -536,7 +537,10 @@ int dev_xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_frame *xdpf,
 		    struct net_device *dev_rx)
 {
-	struct net_device *dev = dst->dev;
+	struct net_device *dev;
+	if (!is_valid_dst(dst, xdpf))
+		return -EINVAL;
+	dev = dst->dev;
 
 	return __xdp_enqueue(dev, xdpf, dev_rx, dst->xdp_prog);
 }
-- 
2.43.0