// For flags

CVE-2024-26865

rds: tcp: Fix use-after-free of net in reqsk_timer_handler().

Severity Score

"-"
*CVSS v-

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track
*SSVC
Descriptions

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

rds: tcp: Fix use-after-free of net in reqsk_timer_handler().

syzkaller reported a warning of netns tracker [0] followed by KASAN
splat [1] and another ref tracker warning [1].

syzkaller could not find a repro, but in the log, the only suspicious
sequence was as follows:

18:26:22 executing program 1:
r0 = socket$inet6_mptcp(0xa, 0x1, 0x106)
...
connect$inet6(r0, &(0x7f0000000080)={0xa, 0x4001, 0x0, @loopback}, 0x1c) (async)

The notable thing here is 0x4001 in connect(), which is RDS_TCP_PORT.

So, the scenario would be:

1. unshare(CLONE_NEWNET) creates a per netns tcp listener in
rds_tcp_listen_init().
2. syz-executor connect()s to it and creates a reqsk.
3. syz-executor exit()s immediately.
4. netns is dismantled. [0]
5. reqsk timer is fired, and UAF happens while freeing reqsk. [1]
6. listener is freed after RCU grace period. [2]

Basically, reqsk assumes that the listener guarantees netns safety
until all reqsk timers are expired by holding the listener's refcount.
However, this was not the case for kernel sockets.

Commit 740ea3c4a0b2 ("tcp: Clean up kernel listener's reqsk in
inet_twsk_purge()") fixed this issue only for per-netns ehash.

Let's apply the same fix for the global ehash.

[0]:
ref_tracker: net notrefcnt@0000000065449cc3 has 1/1 users at
sk_alloc (./include/net/net_namespace.h:337 net/core/sock.c:2146)
inet6_create (net/ipv6/af_inet6.c:192 net/ipv6/af_inet6.c:119)
__sock_create (net/socket.c:1572)
rds_tcp_listen_init (net/rds/tcp_listen.c:279)
rds_tcp_init_net (net/rds/tcp.c:577)
ops_init (net/core/net_namespace.c:137)
setup_net (net/core/net_namespace.c:340)
copy_net_ns (net/core/net_namespace.c:497)
create_new_namespaces (kernel/nsproxy.c:110)
unshare_nsproxy_namespaces (kernel/nsproxy.c:228 (discriminator 4))
ksys_unshare (kernel/fork.c:3429)
__x64_sys_unshare (kernel/fork.c:3496)
do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:129)
...
WARNING: CPU: 0 PID: 27 at lib/ref_tracker.c:179 ref_tracker_dir_exit (lib/ref_tracker.c:179)

[1]:
BUG: KASAN: slab-use-after-free in inet_csk_reqsk_queue_drop (./include/net/inet_hashtables.h:180 net/ipv4/inet_connection_sock.c:952 net/ipv4/inet_connection_sock.c:966)
Read of size 8 at addr ffff88801b370400 by task swapper/0/0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1))
print_report (mm/kasan/report.c:378 mm/kasan/report.c:488)
kasan_report (mm/kasan/report.c:603)
inet_csk_reqsk_queue_drop (./include/net/inet_hashtables.h:180 net/ipv4/inet_connection_sock.c:952 net/ipv4/inet_connection_sock.c:966)
reqsk_timer_handler (net/ipv4/inet_connection_sock.c:979 net/ipv4/inet_connection_sock.c:1092)
call_timer_fn (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/timer.h:127 kernel/time/timer.c:1701)
__run_timers.part.0 (kernel/time/timer.c:1752 kernel/time/timer.c:2038)
run_timer_softirq (kernel/time/timer.c:2053)
__do_softirq (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/irq.h:142 kernel/softirq.c:554)
irq_exit_rcu (kernel/softirq.c:427 kernel/softirq.c:632 kernel/softirq.c:644)
sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1076 (discriminator 14))
</IRQ>

Allocated by task 258 on cpu 0 at 83.612050s:
kasan_save_stack (mm/kasan/common.c:48)
kasan_save_track (mm/kasan/common.c:68)
__kasan_slab_alloc (mm/kasan/common.c:343)
kmem_cache_alloc (mm/slub.c:3813 mm/slub.c:3860 mm/slub.c:3867)
copy_net_ns (./include/linux/slab.h:701 net/core/net_namespace.c:421 net/core/net_namespace.c:480)
create_new_namespaces (kernel/nsproxy.c:110)
unshare_nsproxy_name
---truncated---

En el kernel de Linux se ha resuelto la siguiente vulnerabilidad: rds: tcp: Se corrige el use-after-free de red en reqsk_timer_handler(). syzkaller informó una advertencia de netns tracker [0] seguida de KASAN splat [1] y otra advertencia de ref tracker [1]. syzkaller no pudo encontrar una reproducción, pero en el registro, la única secuencia sospechosa fue la siguiente: 18:26:22 ejecutando el programa 1: r0 = socket$inet6_mptcp(0xa, 0x1, 0x106) ... connect$inet6(r0, &amp;(0x7f0000000080)={0xa, 0x4001, 0x0, @loopback}, 0x1c) (async) Lo notable aquí es 0x4001 en connect(), que es RDS_TCP_PORT. Entonces, el escenario sería: 1. unshare(CLONE_NEWNET) crea un oyente tcp por red en rds_tcp_listen_init(). 2. syz-executor se conecta a él y crea una solicitud. 3. syz-executor sale () inmediatamente. 4. La red está desmantelada. [0] 5. Se activa el temporizador de reqsk y se produce UAF mientras se libera reqsk. [1] 6. El oyente se libera después del período de gracia de RCU. [2] Básicamente, reqsk supone que el oyente garantiza la seguridad de la red hasta que expiren todos los temporizadores de reqsk manteniendo el refcount del oyente. Sin embargo, este no fue el caso de los sockets del kernel. La confirmación 740ea3c4a0b2 ("tcp: Limpiar la solicitud del oyente del kernel en inet_twsk_purge()") solucionó este problema solo para ehash por red. Apliquemos la misma solución para el ehash global. [0]: ref_tracker: net notrefcnt@0000000065449cc3 tiene 1/1 usuarios en sk_alloc (./include/net/net_namespace.h:337 net/core/sock.c:2146) inet6_create (net/ipv6/af_inet6.c:192 net/ipv6/af_inet6.c:119) __sock_create (net/socket.c:1572) rds_tcp_listen_init (net/rds/tcp_listen.c:279) rds_tcp_init_net (net/rds/tcp.c:577) ops_init (net/core/ net_namespace.c:137) setup_net (net/core/net_namespace.c:340) copy_net_ns (net/core/net_namespace.c:497) create_new_namespaces (kernel/nsproxy.c:110) unshare_nsproxy_namespaces (kernel/nsproxy.c:228 ( discriminador 4)) ksys_unshare (kernel/fork.c:3429) __x64_sys_unshare (kernel/fork.c:3496) do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) Entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:129) ... ADVERTENCIA: CPU: 0 PID: 27 en lib/ref_tracker.c:179 ref_tracker_dir_exit (lib/ref_tracker.c:179) [1]: ERROR: KASAN: slab-use-after-free en inet_csk_reqsk_queue_drop (./include/net/inet_hashtables.h:180 net/ipv4/inet_connection_sock.c:952 net/ipv4/inet_connection_sock.c:966) Lectura de tamaño 8 en la dirección ffff88801b370400 mediante el intercambiador de tareas /0/0 Nombre del hardware: PC estándar QEMU (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 01/04/2014 Seguimiento de llamadas: dump_stack_lvl (lib/dump_stack .c:107 (discriminador 1)) print_report (mm/kasan/report.c:378 mm/kasan/report.c:488) kasan_report (mm/kasan/report.c:603) inet_csk_reqsk_queue_drop (./include/net/ inet_hashtables.h:180 net/ipv4/inet_connection_sock.c:952 net/ipv4/inet_connection_sock.c:966) reqsk_timer_handler (net/ipv4/inet_connection_sock.c:979 net/ipv4/inet_connection_sock.c:1092) call_timer_fn (./arch /x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/timer.h:127 kernel/time/timer.c:1701) __run_timers.part. 0 (kernel/time/timer.c:1752 kernel/time/timer.c:2038) run_timer_softirq (kernel/time/timer.c:2053) __do_softirq (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/irq.h:142 kernel/softirq.c:554) irq_exit_rcu (kernel/softirq.c:427 kernel/softirq.c:632 kernel/ softirq.c:644) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1076 (discriminator 14)) Asignado por la tarea 258 en la CPU 0 a 83.612050s: kasan_save_stack (mm/kasan/common.c :48) kasan_save_track (mm/kasan/common.c:68) __kasan_slab_alloc (mm/kasan/common.c:343) kmem_cache_alloc (mm/slub.c:3813 mm/slub.c:3860 mm/slub.c:3867 ) copy_net_ns (./include/linux/slab.h:701 net/core/net_namespace.c:421 net/core/net_namespace.c:480) create_new_namespaces (kernel/nsproxy.c:110) unshare_nsproxy_name ---truncado-- -

*Credits: N/A
CVSS Scores
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* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2024-02-19 CVE Reserved
  • 2024-04-17 CVE Published
  • 2024-04-18 EPSS Updated
  • 2024-12-19 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.3 < 6.1.83
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.3 < 6.1.83"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.3 < 6.6.23
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.3 < 6.6.23"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.3 < 6.7.11
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.3 < 6.7.11"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.3 < 6.8.2
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.3 < 6.8.2"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.3 < 6.9
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.3 < 6.9"
en
Affected