CVE-2021-47555

published 2024-05-24

CVE-2021-47555: In the Linux kernel, the following vulnerability has been resolved: net: vlan: fix underflow for the real_dev refcnt Inject error before dev_hold(real_dev) in…

Priority P4 19 medium 5.5 CVSS 3.1

AV L AC L PR L UI N S U C N I N A H

In the Linux kernel, the following vulnerability has been resolved:

net: vlan: fix underflow for the real_dev refcnt

Inject error before dev_hold(real_dev) in register_vlan_dev(),
and execute the following testcase:

ip link add dev dummy1 type dummy
ip link add name dummy1.100 link dummy1 type vlan id 100
ip link del dev dummy1

When the dummy netdevice is removed, we will get a WARNING as following:

refcount_t: decrement hit 0; leaking memory.
WARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0

and an endless loop of:

unregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824

That is because dev_put(real_dev) in vlan_dev_free() be called without
dev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev
underflow.

Move the dev_hold(real_dev) to vlan_dev_init() which is the call-back of
ndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev
symmetrical.

Affected

20 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 5.15.15-1 (bookworm)	linux 5.15.15-1 (bookworm)
linux	linux	—	—
linux	linux	>= 21032425c36ff85f16e72ca92193a8c401e4acd5 < f7fc72a508cf115c273a7a29350069def1041890	f7fc72a508cf115c273a7a29350069def1041890
linux	linux	>= 5.10.80 < 5.10.83	5.10.83
linux	linux	>= 5.14.19 < 5.15	5.15
linux	linux	>= 5.15.3 < 5.15.6	5.15.6
linux	linux	>= 5.4.160 < 5.4.163	5.4.163
linux	linux	>= 563bcbae3ba233c275c244bfce2efe12938f5363 < 01d9cc2dea3fde3bad6d27f464eff463496e2b00	01d9cc2dea3fde3bad6d27f464eff463496e2b00
linux	linux	>= 700602b662d7eaa816b1a3cb0abe7a85de358fd4 < 5e44178864b38dd70b877985abd7d86fdb95f27d	5e44178864b38dd70b877985abd7d86fdb95f27d
linux	linux	>= e04a7a84bb77f9cdf4475340fe931389bc72331c < 6e800ee43218a56acc93676bbb3d93b74779e555	6e800ee43218a56acc93676bbb3d93b74779e555
linux	linux_kernel	—	—
linux	linux_kernel	—	—
linux	linux_kernel	>= 0 < 5.10.84-1	5.10.84-1
linux	linux_kernel	>= 0 < 5.15.15-1	5.15.15-1
linux	linux_kernel	>= 0 < 5.15.15-1	5.15.15-1
linux	linux_kernel	>= 0 < 5.15.15-1	5.15.15-1
linux	linux_kernel	>= 5.10.80 < 5.10.83	5.10.83
linux	linux_kernel	>= 5.14.19 < 5.15	5.15
linux	linux_kernel	>= 5.15.3 < 5.15.6	5.15.6
linux	linux_kernel	>= 5.4.160 < 5.4.163	5.4.163

CVSS provenance

nvd v3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv 5.5 MEDIUM

vendor_debian 5.5 MEDIUM

vendor_redhat 5.5 MEDIUM

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