[fips-legacy-8] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb #507

shreeya-patel98 · 2025-08-18T11:58:19Z

Commit Message Requirements
Built against Vault/LTS Environment
kABI Check Passed, where Valid (Pre 9.4 RT does not have kABI stability)
Boot Test
Kernel SelfTest results
Additional Tests as determined relevant

Commit message

Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb
jira VULN-8836
cve CVE-2023-40283
commit-author Sungwoo Kim <[email protected]>
commit https://github.com/ctrliq/kernel-src-tree/commit/1728137b33c00d5a2b5110ed7aafb42e7c32e4a1

l2cap_sock_release(sk) frees sk. However, sk's children are still alive
and point to the already free'd sk's address.
To fix this, l2cap_sock_release(sk) also cleans sk's children.

==================================================================
BUG: KASAN: use-after-free in l2cap_sock_ready_cb+0xb7/0x100 net/bluetooth/l2cap_sock.c:1650
Read of size 8 at addr ffff888104617aa8 by task kworker/u3:0/276

CPU: 0 PID: 276 Comm: kworker/u3:0 Not tainted 6.2.0-00001-gef397bd4d5fb-dirty https://github.com/ctrliq/kernel-src-tree/pull/59
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: hci2 hci_rx_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x72/0x95 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:306 [inline]
 print_report+0x175/0x478 mm/kasan/report.c:417
 kasan_report+0xb1/0x130 mm/kasan/report.c:517
 l2cap_sock_ready_cb+0xb7/0x100 net/bluetooth/l2cap_sock.c:1650
 l2cap_chan_ready+0x10e/0x1e0 net/bluetooth/l2cap_core.c:1386
 l2cap_config_req+0x753/0x9f0 net/bluetooth/l2cap_core.c:4480
 l2cap_bredr_sig_cmd net/bluetooth/l2cap_core.c:5739 [inline]
 l2cap_sig_channel net/bluetooth/l2cap_core.c:6509 [inline]
 l2cap_recv_frame+0xe2e/0x43c0 net/bluetooth/l2cap_core.c:7788
 l2cap_recv_acldata+0x6ed/0x7e0 net/bluetooth/l2cap_core.c:8506
 hci_acldata_packet net/bluetooth/hci_core.c:3813 [inline]
 hci_rx_work+0x66e/0xbc0 net/bluetooth/hci_core.c:4048
 process_one_work+0x4ea/0x8e0 kernel/workqueue.c:2289
 worker_thread+0x364/0x8e0 kernel/workqueue.c:2436
 kthread+0x1b9/0x200 kernel/kthread.c:376
 ret_from_fork+0x2c/0x50 arch/x86/entry/entry_64.S:308
 </TASK>

Allocated by task 288:
 kasan_save_stack+0x22/0x50 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x82/0x90 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:968 [inline]
 __kmalloc+0x5a/0x140 mm/slab_common.c:981
 kmalloc include/linux/slab.h:584 [inline]
 sk_prot_alloc+0x113/0x1f0 net/core/sock.c:2040
 sk_alloc+0x36/0x3c0 net/core/sock.c:2093
 l2cap_sock_alloc.constprop.0+0x39/0x1c0 net/bluetooth/l2cap_sock.c:1852
 l2cap_sock_create+0x10d/0x220 net/bluetooth/l2cap_sock.c:1898
 bt_sock_create+0x183/0x290 net/bluetooth/af_bluetooth.c:132
 __sock_create+0x226/0x380 net/socket.c:1518
 sock_create net/socket.c:1569 [inline]
 __sys_socket_create net/socket.c:1606 [inline]
 __sys_socket_create net/socket.c:1591 [inline]
 __sys_socket+0x112/0x200 net/socket.c:1639
 __do_sys_socket net/socket.c:1652 [inline]
 __se_sys_socket net/socket.c:1650 [inline]
 __x64_sys_socket+0x40/0x50 net/socket.c:1650
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3f/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

Freed by task 288:
 kasan_save_stack+0x22/0x50 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:523
 ____kasan_slab_free mm/kasan/common.c:236 [inline]
 ____kasan_slab_free mm/kasan/common.c:200 [inline]
 __kasan_slab_free+0x10a/0x190 mm/kasan/common.c:244
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1781 [inline]
 slab_free_freelist_hook mm/slub.c:1807 [inline]
 slab_free mm/slub.c:3787 [inline]
 __kmem_cache_free+0x88/0x1f0 mm/slub.c:3800
 sk_prot_free net/core/sock.c:2076 [inline]
 __sk_destruct+0x347/0x430 net/core/sock.c:2168
 sk_destruct+0x9c/0xb0 net/core/sock.c:2183
 __sk_free+0x82/0x220 net/core/sock.c:2194
 sk_free+0x7c/0xa0 net/core/sock.c:2205
 sock_put include/net/sock.h:1991 [inline]
 l2cap_sock_kill+0x256/0x2b0 net/bluetooth/l2cap_sock.c:1257
 l2cap_sock_release+0x1a7/0x220 net/bluetooth/l2cap_sock.c:1428
 __sock_release+0x80/0x150 net/socket.c:650
 sock_close+0x19/0x30 net/socket.c:1368
 __fput+0x17a/0x5c0 fs/file_table.c:320
 task_work_run+0x132/0x1c0 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x113/0x120 kernel/entry/common.c:203
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x21/0x50 kernel/entry/common.c:296
 do_syscall_64+0x4c/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

The buggy address belongs to the object at ffff888104617800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 680 bytes inside of
 1024-byte region [ffff888104617800, ffff888104617c00)

The buggy address belongs to the physical page:
page:00000000dbca6a80 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888104614000 pfn:0x104614
head:00000000dbca6a80 order:2 compound_mapcount:0 subpages_mapcount:0 compound_pincount:0
flags: 0x200000000010200(slab|head|node=0|zone=2)
raw: 0200000000010200 ffff888100041dc0 ffffea0004212c10 ffffea0004234b10
raw: ffff888104614000 0000000000080002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888104617980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888104617a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888104617a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff888104617b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888104617b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Ack: This bug is found by FuzzBT with a modified Syzkaller. Other
contributors are Ruoyu Wu and Hui Peng.
	Signed-off-by: Sungwoo Kim <[email protected]>
	Signed-off-by: Luiz Augusto von Dentz <[email protected]>
	Signed-off-by: Jakub Kicinski <[email protected]>
(cherry picked from commit https://github.com/ctrliq/kernel-src-tree/commit/1728137b33c00d5a2b5110ed7aafb42e7c32e4a1)
	Signed-off-by: Shreeya Patel <[email protected]>

Kernel build logs

/mnt/scratch/workspace/fips-legacy-8-compliant/kernel-src-tree
Skipping make mrproper
[TIMER]{MRPROPER}: 0s
x86_64 architecture detected, copying config
'configs/kernel-x86_64.config' -> '.config'
Setting Local Version for build
CONFIG_LOCALVERSION="-shreeya_fips-legacy--165e60c466df"
Making olddefconfig
scripts/kconfig/conf  --olddefconfig Kconfig
#
# configuration written to .config
#
Starting Build
scripts/kconfig/conf  --syncconfig Kconfig
  UPD     include/config/kernel.release
  DESCEND objtool
  DESCEND bpf/resolve_btfids
  UPD     include/generated/utsrelease.h
  CC      arch/x86/kernel/asm-offsets.s
  CALL    scripts/checksyscalls.sh
  CC      arch/x86/ia32/sys_ia32.o
  CC      arch/x86/events/core.o
  CC      init/main.o
  CC 
  [--snip--]
  INSTALL sound/usb/misc/snd-ua101.ko
  INSTALL sound/usb/line6/snd-usb-variax.ko
  INSTALL sound/usb/snd-usb-audio.ko
  INSTALL sound/usb/snd-usbmidi-lib.ko
  INSTALL sound/usb/usx2y/snd-usb-us122l.ko
  INSTALL sound/usb/usx2y/snd-usb-usx2y.ko
  INSTALL sound/virtio/virtio_snd.ko
  INSTALL sound/x86/snd-hdmi-lpe-audio.ko
  INSTALL virt/lib/irqbypass.ko
  INSTALL sound/xen/snd_xen_front.ko
  DEPMOD  4.18.0-shreeya_fips-legacy--165e60c466df+
[TIMER]{MODULES}: 9s
Making Install
sh ./arch/x86/boot/install.sh 4.18.0-shreeya_fips-legacy--165e60c466df+ arch/x86/boot/bzImage \
	System.map "/boot"
[TIMER]{INSTALL}: 16s
Checking kABI
kABI check passed
Setting Default Kernel to  and Index to 0
The default is /boot/loader/entries/1cf5e9bb44ed480cb5927d321c03acfc-4.18.0-shreeya_fips-legacy--165e60c466df+.conf with index 0 and kernel /boot/vmlinuz-4.18.0-shreeya_fips-legacy--165e60c466df+
Generating grub configuration file ...
done
Hopefully Grub2.0 took everything ... rebooting after time metrices
[TIMER]{MRPROPER}: 0s
[TIMER]{BUILD}: 387s
[TIMER]{MODULES}: 9s
[TIMER]{INSTALL}: 16s
[TIMER]{TOTAL} 414s
Rebooting in 10 seconds

kernel-build.log

Kselftests

shreeya@spatel-dev-bom ~/c/w/fips-legacy-8-compliant> grep '^ok ' kselftest-before.log | wc -l && grep '^ok ' kselftest-after.log | wc -l
204
203
shreeya@spatel-dev-bom ~/c/w/fips-legacy-8-compliant> grep '^not ok ' kselftest-before.log | wc -l && grep '^not ok ' kselftest-after.log | wc -l
53
54

Note :- Failure is not related to the change

kselftest-after.log
kselftest-before.log

jira VULN-8836 cve CVE-2023-40283 commit-author Sungwoo Kim <[email protected]> commit 1728137 l2cap_sock_release(sk) frees sk. However, sk's children are still alive and point to the already free'd sk's address. To fix this, l2cap_sock_release(sk) also cleans sk's children. ================================================================== BUG: KASAN: use-after-free in l2cap_sock_ready_cb+0xb7/0x100 net/bluetooth/l2cap_sock.c:1650 Read of size 8 at addr ffff888104617aa8 by task kworker/u3:0/276 CPU: 0 PID: 276 Comm: kworker/u3:0 Not tainted 6.2.0-00001-gef397bd4d5fb-dirty #59 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: hci2 hci_rx_work Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x72/0x95 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:306 [inline] print_report+0x175/0x478 mm/kasan/report.c:417 kasan_report+0xb1/0x130 mm/kasan/report.c:517 l2cap_sock_ready_cb+0xb7/0x100 net/bluetooth/l2cap_sock.c:1650 l2cap_chan_ready+0x10e/0x1e0 net/bluetooth/l2cap_core.c:1386 l2cap_config_req+0x753/0x9f0 net/bluetooth/l2cap_core.c:4480 l2cap_bredr_sig_cmd net/bluetooth/l2cap_core.c:5739 [inline] l2cap_sig_channel net/bluetooth/l2cap_core.c:6509 [inline] l2cap_recv_frame+0xe2e/0x43c0 net/bluetooth/l2cap_core.c:7788 l2cap_recv_acldata+0x6ed/0x7e0 net/bluetooth/l2cap_core.c:8506 hci_acldata_packet net/bluetooth/hci_core.c:3813 [inline] hci_rx_work+0x66e/0xbc0 net/bluetooth/hci_core.c:4048 process_one_work+0x4ea/0x8e0 kernel/workqueue.c:2289 worker_thread+0x364/0x8e0 kernel/workqueue.c:2436 kthread+0x1b9/0x200 kernel/kthread.c:376 ret_from_fork+0x2c/0x50 arch/x86/entry/entry_64.S:308 </TASK> Allocated by task 288: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 ____kasan_kmalloc mm/kasan/common.c:374 [inline] __kasan_kmalloc+0x82/0x90 mm/kasan/common.c:383 kasan_kmalloc include/linux/kasan.h:211 [inline] __do_kmalloc_node mm/slab_common.c:968 [inline] __kmalloc+0x5a/0x140 mm/slab_common.c:981 kmalloc include/linux/slab.h:584 [inline] sk_prot_alloc+0x113/0x1f0 net/core/sock.c:2040 sk_alloc+0x36/0x3c0 net/core/sock.c:2093 l2cap_sock_alloc.constprop.0+0x39/0x1c0 net/bluetooth/l2cap_sock.c:1852 l2cap_sock_create+0x10d/0x220 net/bluetooth/l2cap_sock.c:1898 bt_sock_create+0x183/0x290 net/bluetooth/af_bluetooth.c:132 __sock_create+0x226/0x380 net/socket.c:1518 sock_create net/socket.c:1569 [inline] __sys_socket_create net/socket.c:1606 [inline] __sys_socket_create net/socket.c:1591 [inline] __sys_socket+0x112/0x200 net/socket.c:1639 __do_sys_socket net/socket.c:1652 [inline] __se_sys_socket net/socket.c:1650 [inline] __x64_sys_socket+0x40/0x50 net/socket.c:1650 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3f/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x72/0xdc Freed by task 288: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:523 ____kasan_slab_free mm/kasan/common.c:236 [inline] ____kasan_slab_free mm/kasan/common.c:200 [inline] __kasan_slab_free+0x10a/0x190 mm/kasan/common.c:244 kasan_slab_free include/linux/kasan.h:177 [inline] slab_free_hook mm/slub.c:1781 [inline] slab_free_freelist_hook mm/slub.c:1807 [inline] slab_free mm/slub.c:3787 [inline] __kmem_cache_free+0x88/0x1f0 mm/slub.c:3800 sk_prot_free net/core/sock.c:2076 [inline] __sk_destruct+0x347/0x430 net/core/sock.c:2168 sk_destruct+0x9c/0xb0 net/core/sock.c:2183 __sk_free+0x82/0x220 net/core/sock.c:2194 sk_free+0x7c/0xa0 net/core/sock.c:2205 sock_put include/net/sock.h:1991 [inline] l2cap_sock_kill+0x256/0x2b0 net/bluetooth/l2cap_sock.c:1257 l2cap_sock_release+0x1a7/0x220 net/bluetooth/l2cap_sock.c:1428 __sock_release+0x80/0x150 net/socket.c:650 sock_close+0x19/0x30 net/socket.c:1368 __fput+0x17a/0x5c0 fs/file_table.c:320 task_work_run+0x132/0x1c0 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0x113/0x120 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x21/0x50 kernel/entry/common.c:296 do_syscall_64+0x4c/0x90 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x72/0xdc The buggy address belongs to the object at ffff888104617800 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 680 bytes inside of 1024-byte region [ffff888104617800, ffff888104617c00) The buggy address belongs to the physical page: page:00000000dbca6a80 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888104614000 pfn:0x104614 head:00000000dbca6a80 order:2 compound_mapcount:0 subpages_mapcount:0 compound_pincount:0 flags: 0x200000000010200(slab|head|node=0|zone=2) raw: 0200000000010200 ffff888100041dc0 ffffea0004212c10 ffffea0004234b10 raw: ffff888104614000 0000000000080002 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888104617980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888104617a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888104617a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888104617b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888104617b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Ack: This bug is found by FuzzBT with a modified Syzkaller. Other contributors are Ruoyu Wu and Hui Peng. Signed-off-by: Sungwoo Kim <[email protected]> Signed-off-by: Luiz Augusto von Dentz <[email protected]> Signed-off-by: Jakub Kicinski <[email protected]> (cherry picked from commit 1728137) Signed-off-by: Shreeya Patel <[email protected]>

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shreeya-patel98 requested review from kerneltoast, PlaidCat, bmastbergen and thefossguy-ciq August 18, 2025 11:58

shreeya-patel98 self-assigned this Aug 18, 2025

shreeya-patel98 changed the title ~~[fips-lagacy-8-complaint] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb~~ [fips-legacy-8-compliant] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb Aug 18, 2025

shreeya-patel98 changed the title ~~[fips-legacy-8-compliant] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb~~ [fips-legacy-8] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb Aug 18, 2025

thefossguy-ciq approved these changes Aug 18, 2025

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bmastbergen approved these changes Aug 18, 2025

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shreeya-patel98 merged commit 9b921b6 into fips-legacy-8-compliant/4.18.0-425.13.1 Aug 19, 2025
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shreeya-patel98 deleted the {shreeya}_fips-legacy-8-compliant/4.18.0-425.13.1 branch August 19, 2025 09:49

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[fips-legacy-8] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb #507

[fips-legacy-8] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb #507

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[fips-legacy-8] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb #507

[fips-legacy-8] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready_cb #507

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shreeya-patel98 commented Aug 18, 2025

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Kselftests

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