Bug 2322312 (CVE-2024-50073)

Summary:	CVE-2024-50073 kernel: tty: n_gsm: Fix use-after-free in gsm_cleanup_mux
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dfreiber, drow, jburrell, vkumar
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	A user after free vulnerability exists in the linux kernel such that when gsm_cleanup_mux is called,the gsm_msg on the tx_ctrl_list is not freed,resulting in loss of availability of the system.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2322356
Bug Blocks:

Description OSIDB Bzimport 2024-10-29 01:01:50 UTC

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

tty: n_gsm: Fix use-after-free in gsm_cleanup_mux

BUG: KASAN: slab-use-after-free in gsm_cleanup_mux+0x77b/0x7b0
drivers/tty/n_gsm.c:3160 [n_gsm]
Read of size 8 at addr ffff88815fe99c00 by task poc/3379
CPU: 0 UID: 0 PID: 3379 Comm: poc Not tainted 6.11.0+ #56
Hardware name: VMware, Inc. VMware Virtual Platform/440BX
Desktop Reference Platform, BIOS 6.00 11/12/2020
Call Trace:
 <TASK>
 gsm_cleanup_mux+0x77b/0x7b0 drivers/tty/n_gsm.c:3160 [n_gsm]
 __pfx_gsm_cleanup_mux+0x10/0x10 drivers/tty/n_gsm.c:3124 [n_gsm]
 __pfx_sched_clock_cpu+0x10/0x10 kernel/sched/clock.c:389
 update_load_avg+0x1c1/0x27b0 kernel/sched/fair.c:4500
 __pfx_min_vruntime_cb_rotate+0x10/0x10 kernel/sched/fair.c:846
 __rb_insert_augmented+0x492/0xbf0 lib/rbtree.c:161
 gsmld_ioctl+0x395/0x1450 drivers/tty/n_gsm.c:3408 [n_gsm]
 _raw_spin_lock_irqsave+0x92/0xf0 arch/x86/include/asm/atomic.h:107
 __pfx_gsmld_ioctl+0x10/0x10 drivers/tty/n_gsm.c:3822 [n_gsm]
 ktime_get+0x5e/0x140 kernel/time/timekeeping.c:195
 ldsem_down_read+0x94/0x4e0 arch/x86/include/asm/atomic64_64.h:79
 __pfx_ldsem_down_read+0x10/0x10 drivers/tty/tty_ldsem.c:338
 __pfx_do_vfs_ioctl+0x10/0x10 fs/ioctl.c:805
 tty_ioctl+0x643/0x1100 drivers/tty/tty_io.c:2818

Allocated by task 65:
 gsm_data_alloc.constprop.0+0x27/0x190 drivers/tty/n_gsm.c:926 [n_gsm]
 gsm_send+0x2c/0x580 drivers/tty/n_gsm.c:819 [n_gsm]
 gsm1_receive+0x547/0xad0 drivers/tty/n_gsm.c:3038 [n_gsm]
 gsmld_receive_buf+0x176/0x280 drivers/tty/n_gsm.c:3609 [n_gsm]
 tty_ldisc_receive_buf+0x101/0x1e0 drivers/tty/tty_buffer.c:391
 tty_port_default_receive_buf+0x61/0xa0 drivers/tty/tty_port.c:39
 flush_to_ldisc+0x1b0/0x750 drivers/tty/tty_buffer.c:445
 process_scheduled_works+0x2b0/0x10d0 kernel/workqueue.c:3229
 worker_thread+0x3dc/0x950 kernel/workqueue.c:3391
 kthread+0x2a3/0x370 kernel/kthread.c:389
 ret_from_fork+0x2d/0x70 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:257

Freed by task 3367:
 kfree+0x126/0x420 mm/slub.c:4580
 gsm_cleanup_mux+0x36c/0x7b0 drivers/tty/n_gsm.c:3160 [n_gsm]
 gsmld_ioctl+0x395/0x1450 drivers/tty/n_gsm.c:3408 [n_gsm]
 tty_ioctl+0x643/0x1100 drivers/tty/tty_io.c:2818

[Analysis]
gsm_msg on the tx_ctrl_list or tx_data_list of gsm_mux
can be freed by multi threads through ioctl,which leads
to the occurrence of uaf. Protect it by gsm tx lock.

Comment 1 Michal Findra 2024-10-29 07:37:31 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2024102935-CVE-2024-50073-307b@gregkh/T

Comment 2 errata-xmlrpc 2025-05-13 08:31:58 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2025:6966 https://access.redhat.com/errata/RHSA-2025:6966