Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:[EOL][EOL]comedi: check device's attached status in compat ioctls[EOL][EOL]Syzbot identified an issue [1] that crashes kernel, seemingly due to[EOL]unexistent callback dev->get_valid_routes(). By all means, this should[EOL]not occur as said callback must always be set to[EOL]get_zero_valid_routes() in __comedi_device_postconfig().[EOL][EOL]As the crash seems to appear exclusively in i386 kernels, at least,[EOL]judging from [1] reports, the blame lies with compat versions[EOL]of standard IOCTL handlers. Several of them are modified and[EOL]do not use comedi_unlocked_ioctl(). While functionality of these[EOL]ioctls essentially copy their original versions, they do not[EOL]have required sanity check for device's attached status. This,[EOL]in turn, leads to a possibility of calling select IOCTLs on a[EOL]device that has not been properly setup, even via COMEDI_DEVCONFIG.[EOL][EOL]Doing so on unconfigured devices means that several crucial steps[EOL]are missed, for instance, specifying dev->get_valid_routes()[EOL]callback.[EOL][EOL]Fix this somewhat crudely by ensuring device's attached status before[EOL]performing any ioctls, improving logic consistency between modern[EOL]and compat functions.[EOL][EOL][1] Syzbot report:[EOL]BUG: kernel NULL pointer dereference, address: 0000000000000000[EOL]...[EOL]CR2: ffffffffffffffd6 CR3: 000000006c717000 CR4: 0000000000352ef0[EOL]Call Trace:[EOL] <TASK>[EOL] get_valid_routes drivers/comedi/comedi_fops.c:1322 [inline][EOL] parse_insn+0x78c/0x1970 drivers/comedi/comedi_fops.c:1401[EOL] do_insnlist_ioctl+0x272/0x700 drivers/comedi/comedi_fops.c:1594[EOL] compat_insnlist drivers/comedi/comedi_fops.c:3208 [inline][EOL] comedi_compat_ioctl+0x810/0x990 drivers/comedi/comedi_fops.c:3273[EOL] __do_compat_sys_ioctl fs/ioctl.c:695 [inline][EOL] __se_compat_sys_ioctl fs/ioctl.c:638 [inline][EOL] __ia32_compat_sys_ioctl+0x242/0x370 fs/ioctl.c:638[EOL] do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline][EOL]...