Subject: CVE-2024-27399: Bluetooth: l2cap: fix null-ptr-deref in l2cap_chan_timeout

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

Bluetooth: l2cap: fix null-ptr-deref in l2cap_chan_timeout

There is a race condition between l2cap_chan_timeout() and
l2cap_chan_del(). When we use l2cap_chan_del() to delete the
channel, the chan->conn will be set to null. But the conn could
be dereferenced again in the mutex_lock() of l2cap_chan_timeout().
As a result the null pointer dereference bug will happen. The
KASAN report triggered by POC is shown below:

[  472.074580] ==================================================================
[  472.075284] BUG: KASAN: null-ptr-deref in mutex_lock+0x68/0xc0
[  472.075308] Write of size 8 at addr 0000000000000158 by task kworker/0:0/7
[  472.075308]
[  472.075308] CPU: 0 PID: 7 Comm: kworker/0:0 Not tainted 6.9.0-rc5-00356-g78c0094a146b #36
[  472.075308] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu4
[  472.075308] Workqueue: events l2cap_chan_timeout
[  472.075308] Call Trace:
[  472.075308]  <TASK>
[  472.075308]  dump_stack_lvl+0x137/0x1a0
[  472.075308]  print_report+0x101/0x250
[  472.075308]  ? __virt_addr_valid+0x77/0x160
[  472.075308]  ? mutex_lock+0x68/0xc0
[  472.075308]  kasan_report+0x139/0x170
[  472.075308]  ? mutex_lock+0x68/0xc0
[  472.075308]  kasan_check_range+0x2c3/0x2e0
[  472.075308]  mutex_lock+0x68/0xc0
[  472.075308]  l2cap_chan_timeout+0x181/0x300
[  472.075308]  process_one_work+0x5d2/0xe00
[  472.075308]  worker_thread+0xe1d/0x1660
[  472.075308]  ? pr_cont_work+0x5e0/0x5e0
[  472.075308]  kthread+0x2b7/0x350
[  472.075308]  ? pr_cont_work+0x5e0/0x5e0
[  472.075308]  ? kthread_blkcg+0xd0/0xd0
[  472.075308]  ret_from_fork+0x4d/0x80
[  472.075308]  ? kthread_blkcg+0xd0/0xd0
[  472.075308]  ret_from_fork_asm+0x11/0x20
[  472.075308]  </TASK>
[  472.075308] ==================================================================
[  472.094860] Disabling lock debugging due to kernel taint
[  472.096136] BUG: kernel NULL pointer dereference, address: 0000000000000158
[  472.096136] #PF: supervisor write access in kernel mode
[  472.096136] #PF: error_code(0x0002) - not-present page
[  472.096136] PGD 0 P4D 0
[  472.096136] Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI
[  472.096136] CPU: 0 PID: 7 Comm: kworker/0:0 Tainted: G    B              6.9.0-rc5-00356-g78c0094a146b #36
[  472.096136] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu4
[  472.096136] Workqueue: events l2cap_chan_timeout
[  472.096136] RIP: 0010:mutex_lock+0x88/0xc0
[  472.096136] Code: be 08 00 00 00 e8 f8 23 1f fd 4c 89 f7 be 08 00 00 00 e8 eb 23 1f fd 42 80 3c 23 00 74 08 48 88
[  472.096136] RSP: 0018:ffff88800744fc78 EFLAGS: 00000246
[  472.096136] RAX: 0000000000000000 RBX: 1ffff11000e89f8f RCX: ffffffff8457c865
[  472.096136] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff88800744fc78
[  472.096136] RBP: 0000000000000158 R08: ffff88800744fc7f R09: 1ffff11000e89f8f
[  472.096136] R10: dffffc0000000000 R11: ffffed1000e89f90 R12: dffffc0000000000
[  472.096136] R13: 0000000000000158 R14: ffff88800744fc78 R15: ffff888007405a00
[  472.096136] FS:  0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
[  472.096136] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  472.096136] CR2: 0000000000000158 CR3: 000000000da32000 CR4: 00000000000006f0
[  472.096136] Call Trace:
[  472.096136]  <TASK>
[  472.096136]  ? __die_body+0x8d/0xe0
[  472.096136]  ? page_fault_oops+0x6b8/0x9a0
[  472.096136]  ? kernelmode_fixup_or_oops+0x20c/0x2a0
[  472.096136]  ? do_user_addr_fault+0x1027/0x1340
[  472.096136]  ? _printk+0x7a/0xa0
[  472.096136]  ? mutex_lock+0x68/0xc0
[  472.096136]  ? add_taint+0x42/0xd0
[  472.096136]  ? exc_page_fault+0x6a/0x1b0
[  472.096136]  ? asm_exc_page_fault+0x26/0x30
[  472.096136]  ? mutex_lock+0x75/0xc0
[  472.096136]  ? mutex_lock+0x88/0xc0
[  472.096136]  ? mutex_lock+0x75/0xc0
[  472.096136]  l2cap_chan_timeout+0x181/0x300
[  472.096136]  process_one_work+0x5d2/0xe00
[  472.096136]  worker_thread+0xe1d/0x1660
[  472.096136]  ? pr_cont_work+0x5e0/0x5e0
[  472.096136]  kthread+0x2b7/0x350
[  472.096136]  ? pr_cont_work+0x5e0/0x5e0
[  472.096136]  ? kthread_blkcg+0xd0/0xd0
[  472.096136]  ret_from_fork+0x4d/0x80
[  472.096136]  ? kthread_blkcg+0xd0/0xd0
[  472.096136]  ret_from_fork_asm+0x11/0x20
[  472.096136]  </TASK>
[  472.096136] Modules linked in:
[  472.096136] CR2: 0000000000000158
[  472.096136] ---[ end trace 0000000000000000 ]---
[  472.096136] RIP: 0010:mutex_lock+0x88/0xc0
[  472.096136] Code: be 08 00 00 00 e8 f8 23 1f fd 4c 89 f7 be 08 00 00 00 e8 eb 23 1f fd 42 80 3c 23 00 74 08 48 88
[  472.096136] RSP: 0018:ffff88800744fc78 EFLAGS: 00000246
[  472.096136] RAX: 0000000000000000 RBX: 1ffff11000e89f8f RCX: ffffffff8457c865
[  472.096136] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff88800744fc78
[  472.096136] RBP: 0000000000000158 R08: ffff88800744fc7f R09: 1ffff11000e89f8f
[  472.132932] R10: dffffc0000000000 R11: ffffed1000e89f90 R12: dffffc0000000000
[  472.132932] R13: 0000000000000158 R14: ffff88800744fc78 R15: ffff888007405a00
[  472.132932] FS:  0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
[  472.132932] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  472.132932] CR2: 0000000000000158 CR3: 000000000da32000 CR4: 00000000000006f0
[  472.132932] Kernel panic - not syncing: Fatal exception
[  472.132932] Kernel Offset: disabled
[  472.132932] ---[ end Kernel panic - not syncing: Fatal exception ]---

Add a check to judge whether the conn is null in l2cap_chan_timeout()
in order to mitigate the bug.

The Linux kernel CVE team has assigned CVE-2024-27399 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 4.19.314 with commit e137e2ba96e5
	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 5.4.276 with commit 6466ee65e5b2
	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 5.10.217 with commit 06acb75e7ed6
	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 5.15.159 with commit e97e16433eb4
	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 6.1.91 with commit 8960ff650aec
	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 6.6.31 with commit 955b5b6c54d9
	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 6.8.10 with commit eb86f955488c
	Issue introduced in 3.4 with commit 3df91ea20e74 and fixed in 6.9 with commit adf0398cee86

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-27399
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/bluetooth/l2cap_core.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e137e2ba96e51902dc2878131823a96bf8e638ae
	https://git.kernel.org/stable/c/6466ee65e5b27161c846c73ef407f49dfa1bd1d9
	https://git.kernel.org/stable/c/06acb75e7ed600d0bbf7bff5628aa8f24a97978c
	https://git.kernel.org/stable/c/e97e16433eb4533083b096a3824b93a5ca3aee79
	https://git.kernel.org/stable/c/8960ff650aec70485b40771cd8e6e8c4cb467d33
	https://git.kernel.org/stable/c/955b5b6c54d95b5e7444dfc81c95c8e013f27ac0
	https://git.kernel.org/stable/c/eb86f955488c39526534211f2610e48a5cf8ead4
	https://git.kernel.org/stable/c/adf0398cee86643b8eacde95f17d073d022f782c