CVE-2024-50073

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

tty: ngsm: Fix use-after-free in gsmcleanup_mux

BUG: KASAN: slab-use-after-free in gsmcleanupmux+0x77b/0x7b0 drivers/tty/ngsm.c:3160 [ngsm] 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> gsmcleanupmux+0x77b/0x7b0 drivers/tty/ngsm.c:3160 [ngsm] __pfxgsmcleanup_mux+0x10/0x10 drivers/tty/ngsm.c:3124 [ngsm] __pfxschedclock_cpu+0x10/0x10 kernel/sched/clock.c:389 updateloadavg+0x1c1/0x27b0 kernel/sched/fair.c:4500 __pfxminvruntimecbrotate+0x10/0x10 kernel/sched/fair.c:846 __rbinsertaugmented+0x492/0xbf0 lib/rbtree.c:161 gsmldioctl+0x395/0x1450 drivers/tty/ngsm.c:3408 [ngsm] rawspinlock_irqsave+0x92/0xf0 arch/x86/include/asm/atomic.h:107 __pfxgsmldioctl+0x10/0x10 drivers/tty/ngsm.c:3822 [ngsm] ktimeget+0x5e/0x140 kernel/time/timekeeping.c:195 ldsemdownread+0x94/0x4e0 arch/x86/include/asm/atomic6464.h:79 __pfxldsemdownread+0x10/0x10 drivers/tty/ttyldsem.c:338 _pfxdovfsioctl+0x10/0x10 fs/ioctl.c:805 ttyioctl+0x643/0x1100 drivers/tty/ttyio.c:2818

Allocated by task 65: gsmdataalloc.constprop.0+0x27/0x190 drivers/tty/ngsm.c:926 [ngsm] gsmsend+0x2c/0x580 drivers/tty/ngsm.c:819 [ngsm] gsm1receive+0x547/0xad0 drivers/tty/ngsm.c:3038 [ngsm] gsmldreceivebuf+0x176/0x280 drivers/tty/ngsm.c:3609 [ngsm] ttyldiscreceivebuf+0x101/0x1e0 drivers/tty/ttybuffer.c:391 ttyportdefaultreceivebuf+0x61/0xa0 drivers/tty/ttyport.c:39 flushtoldisc+0x1b0/0x750 drivers/tty/ttybuffer.c:445 processscheduledworks+0x2b0/0x10d0 kernel/workqueue.c:3229 workerthread+0x3dc/0x950 kernel/workqueue.c:3391 kthread+0x2a3/0x370 kernel/kthread.c:389 retfromfork+0x2d/0x70 arch/x86/kernel/process.c:147 retfromforkasm+0x1a/0x30 arch/x86/entry/entry_64.S:257

Freed by task 3367: kfree+0x126/0x420 mm/slub.c:4580 gsmcleanupmux+0x36c/0x7b0 drivers/tty/ngsm.c:3160 [ngsm] gsmldioctl+0x395/0x1450 drivers/tty/ngsm.c:3408 [ngsm] ttyioctl+0x643/0x1100 drivers/tty/tty_io.c:2818

[Analysis] gsmmsg on the txctrllist or txdatalist of gsmmux can be freed by multi threads through ioctl,which leads to the occurrence of uaf. Protect it by gsm tx lock.