CVE-2024-26875

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

media: pvrusb2: fix uaf in pvr2contextset_notify

[Syzbot reported] BUG: KASAN: slab-use-after-free in pvr2contextset_notify+0x2c4/0x310 drivers/media/usb/pvrusb2/pvrusb2-context.c:35 Read of size 4 at addr ffff888113aeb0d8 by task kworker/1:1/26

CPU: 1 PID: 26 Comm: kworker/1:1 Not tainted 6.8.0-rc1-syzkaller-00046-gf1a27f081c1f #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 Workqueue: usbhubwq hubevent Call Trace: <TASK> _dumpstack lib/dumpstack.c:88 [inline] dumpstacklvl+0xd9/0x1b0 lib/dumpstack.c:106 printaddressdescription mm/kasan/report.c:377 [inline] printreport+0xc4/0x620 mm/kasan/report.c:488 kasanreport+0xda/0x110 mm/kasan/report.c:601 pvr2contextsetnotify+0x2c4/0x310 drivers/media/usb/pvrusb2/pvrusb2-context.c:35 pvr2contextnotify drivers/media/usb/pvrusb2/pvrusb2-context.c:95 [inline] pvr2contextdisconnect+0x94/0xb0 drivers/media/usb/pvrusb2/pvrusb2-context.c:272

Freed by task 906: kasansavestack+0x33/0x50 mm/kasan/common.c:47 kasansavetrack+0x14/0x30 mm/kasan/common.c:68 kasansavefreeinfo+0x3f/0x60 mm/kasan/generic.c:640 poisonslabobject mm/kasan/common.c:241 [inline] _kasanslabfree+0x106/0x1b0 mm/kasan/common.c:257 kasanslabfree include/linux/kasan.h:184 [inline] slabfreehook mm/slub.c:2121 [inline] slabfree mm/slub.c:4299 [inline] kfree+0x105/0x340 mm/slub.c:4409 pvr2contextcheck drivers/media/usb/pvrusb2/pvrusb2-context.c:137 [inline] pvr2contextthreadfunc+0x69d/0x960 drivers/media/usb/pvrusb2/pvrusb2-context.c:158

[Analyze] Task A set disconnect_flag = !0, which resulted in Task B's condition being met and releasing mp, leading to this issue.

[Fix] Place the disconnectflag assignment operation after all code in pvr2context_disconnect() to avoid this issue.