netns: Make get_net_ns() handle zero refcount net

PlaidCat · PlaidCat · commit d3a57c78796d · 2024-09-12T13:27:04.000-04:00
jira LE-1907 cve CVE-2024-40958 Rebuild_History Non-Buildable kernel-5.14.0-427.31.1.el9_4 commit-author Yue Haibing <yuehaibing@huawei.com> commit ff960f9 Syzkaller hit a warning: refcount_t: addition on 0; use-after-free. WARNING: CPU: 3 PID: 7890 at lib/refcount.c:25 refcount_warn_saturate+0xdf/0x1d0 Modules linked in: CPU: 3 PID: 7890 Comm: tun Not tainted 6.10.0-rc3-00100-gcaa4f9578aba-dirty ctrliq#310 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:refcount_warn_saturate+0xdf/0x1d0 Code: 41 49 04 31 ff 89 de e8 9f 1e cd fe 84 db 75 9c e8 76 26 cd fe c6 05 b6 41 49 04 01 90 48 c7 c7 b8 8e 25 86 e8 d2 05 b5 fe 90 <0f> 0b 90 90 e9 79 ff ff ff e8 53 26 cd fe 0f b6 1 RSP: 0018:ffff8881067b7da0 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff811c72ac RDX: ffff8881026a2140 RSI: ffffffff811c72b5 RDI: 0000000000000001 RBP: ffff8881067b7db0 R08: 0000000000000000 R09: 205b5d3730353139 R10: 0000000000000000 R11: 205d303938375420 R12: ffff8881086500c4 R13: ffff8881086500c4 R14: ffff8881086500b0 R15: ffff888108650040 FS: 00007f5b2961a4c0(0000) GS:ffff88823bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055d7ed36fd18 CR3: 00000001482f6000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? show_regs+0xa3/0xc0 ? __warn+0xa5/0x1c0 ? refcount_warn_saturate+0xdf/0x1d0 ? report_bug+0x1fc/0x2d0 ? refcount_warn_saturate+0xdf/0x1d0 ? handle_bug+0xa1/0x110 ? exc_invalid_op+0x3c/0xb0 ? asm_exc_invalid_op+0x1f/0x30 ? __warn_printk+0xcc/0x140 ? __warn_printk+0xd5/0x140 ? refcount_warn_saturate+0xdf/0x1d0 get_net_ns+0xa4/0xc0 ? __pfx_get_net_ns+0x10/0x10 open_related_ns+0x5a/0x130 __tun_chr_ioctl+0x1616/0x2370 ? __sanitizer_cov_trace_switch+0x58/0xa0 ? __sanitizer_cov_trace_const_cmp2+0x1c/0x30 ? __pfx_tun_chr_ioctl+0x10/0x10 tun_chr_ioctl+0x2f/0x40 __x64_sys_ioctl+0x11b/0x160 x64_sys_call+0x1211/0x20d0 do_syscall_64+0x9e/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5b28f165d7 Code: b3 66 90 48 8b 05 b1 48 2d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 81 48 2d 00 8 RSP: 002b:00007ffc2b59c5e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5b28f165d7 RDX: 0000000000000000 RSI: 00000000000054e3 RDI: 0000000000000003 RBP: 00007ffc2b59c650 R08: 00007f5b291ed8c0 R09: 00007f5b2961a4c0 R10: 0000000029690010 R11: 0000000000000246 R12: 0000000000400730 R13: 00007ffc2b59cf40 R14: 0000000000000000 R15: 0000000000000000 </TASK> Kernel panic - not syncing: kernel: panic_on_warn set ... This is trigger as below: ns0 ns1 tun_set_iff() //dev is tun0 tun->dev = dev //ip link set tun0 netns ns1 put_net() //ref is 0 __tun_chr_ioctl() //TUNGETDEVNETNS net = dev_net(tun->dev); open_related_ns(&net->ns, get_net_ns); //ns1 get_net_ns() get_net() //addition on 0 Use maybe_get_net() in get_net_ns in case net's ref is zero to fix this Fixes: 0c3e0e3 ("tun: Add ioctl() TUNGETDEVNETNS cmd to allow obtaining real net ns of tun device") Signed-off-by: Yue Haibing <yuehaibing@huawei.com> Link: https://lore.kernel.org/r/20240614131302.2698509-1-yuehaibing@huawei.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> (cherry picked from commit ff960f9) Signed-off-by: Jonathan Maple <jmaple@ciq.com>
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
@@ -654,11 +654,16 @@ EXPORT_SYMBOL_GPL(__put_net);
  * get_net_ns - increment the refcount of the network namespace
  * @ns: common namespace (net)
  *
- * Returns the net's common namespace.
+ * Returns the net's common namespace or ERR_PTR() if ref is zero.
  */
 struct ns_common *get_net_ns(struct ns_common *ns)
 {
-	return &get_net(container_of(ns, struct net, ns))->ns;
+	struct net *net;
+
+	net = maybe_get_net(container_of(ns, struct net, ns));
+	if (net)
+		return &net->ns;
+	return ERR_PTR(-EINVAL);
 }
 EXPORT_SYMBOL_GPL(get_net_ns);
 

Original file line number	Diff line number	Diff line change
`@@ -654,11 +654,16 @@ EXPORT_SYMBOL_GPL(__put_net);`
`654`	`654`	`* get_net_ns - increment the refcount of the network namespace`
`655`	`655`	`* @ns: common namespace (net)`
`656`	`656`	`*`
`657`		`- * Returns the net's common namespace.`
	`657`	`+ * Returns the net's common namespace or ERR_PTR() if ref is zero.`
`658`	`658`	`*/`
`659`	`659`	`struct ns_common get_net_ns(struct ns_common ns)`
`660`	`660`	`{`
`661`		`- return &get_net(container_of(ns, struct net, ns))->ns;`
	`661`	`+ struct net *net;`
	`662`	`+`
	`663`	`+ net = maybe_get_net(container_of(ns, struct net, ns));`
	`664`	`+ if (net)`
	`665`	`+ return &net->ns;`
	`666`	`+ return ERR_PTR(-EINVAL);`
`662`	`667`	`}`
`663`	`668`	`EXPORT_SYMBOL_GPL(get_net_ns);`
`664`	`669`