On Fri, Jul 24, 2020 at 11:03:54PM -0700, Nathan Chancellor wrote:
When booting up on a Raspberry Pi 4 with Control Flow Integrity checking enabled, the following warning/panic happens:
[ 1.626435] CFI failure (target: dwc2_set_bcm_params+0x0/0x4): [ 1.632408] WARNING: CPU: 0 PID: 32 at kernel/cfi.c:30 __cfi_check_fail+0x54/0x5c [ 1.640021] Modules linked in: [ 1.643137] CPU: 0 PID: 32 Comm: kworker/0:1 Not tainted 5.8.0-rc6-next-20200724-00051-g89ba619726de #1 [ 1.652693] Hardware name: Raspberry Pi 4 Model B Rev 1.2 (DT) [ 1.658637] Workqueue: events deferred_probe_work_func [ 1.663870] pstate: 60000005 (nZCv daif -PAN -UAO BTYPE=--) [ 1.669542] pc : __cfi_check_fail+0x54/0x5c [ 1.673798] lr : __cfi_check_fail+0x54/0x5c [ 1.678050] sp : ffff8000102bbaa0 [ 1.681419] x29: ffff8000102bbaa0 x28: ffffab09e21c7000 [ 1.686829] x27: 0000000000000402 x26: ffff0000f6e7c228 [ 1.692238] x25: 00000000fb7cdb0d x24: 0000000000000005 [ 1.697647] x23: ffffab09e2515000 x22: ffffab09e069a000 [ 1.703055] x21: 4c550309df1cf4c1 x20: ffffab09e2433c60 [ 1.708462] x19: ffffab09e160dc50 x18: ffff0000f6e8cc78 [ 1.713870] x17: 0000000000000041 x16: ffffab09e0bce6f8 [ 1.719278] x15: ffffab09e1c819b7 x14: 0000000000000003 [ 1.724686] x13: 00000000ffffefff x12: 0000000000000000 [ 1.730094] x11: 0000000000000000 x10: 00000000ffffffff [ 1.735501] x9 : c932f7abfc4bc600 x8 : c932f7abfc4bc600 [ 1.740910] x7 : 077207610770075f x6 : ffff0000f6c38f00 [ 1.746317] x5 : 0000000000000000 x4 : 0000000000000000 [ 1.751723] x3 : 0000000000000000 x2 : 0000000000000000 [ 1.757129] x1 : ffff8000102bb7d8 x0 : 0000000000000032 [ 1.762539] Call trace: [ 1.765030] __cfi_check_fail+0x54/0x5c [ 1.768938] __cfi_check+0x5fa6c/0x66afc [ 1.772932] dwc2_init_params+0xd74/0xd78 [ 1.777012] dwc2_driver_probe+0x484/0x6ec [ 1.781180] platform_drv_probe+0xb4/0x100 [ 1.785350] really_probe+0x228/0x63c [ 1.789076] driver_probe_device+0x80/0xc0 [ 1.793247] __device_attach_driver+0x114/0x160 [ 1.797857] bus_for_each_drv+0xa8/0x128 [ 1.801851] __device_attach.llvm.14901095709067289134+0xc0/0x170 [ 1.808050] bus_probe_device+0x44/0x100 [ 1.812044] deferred_probe_work_func+0x78/0xb8 [ 1.816656] process_one_work+0x204/0x3c4 [ 1.820736] worker_thread+0x2f0/0x4c4 [ 1.824552] kthread+0x174/0x184 [ 1.827837] ret_from_fork+0x10/0x18
CFI validates that all indirect calls go to a function with the same exact function pointer prototype. In this case, dwc2_set_bcm_params is the target, which has a parameter of type 'struct dwc2_hsotg *', but it is being implicitly cast to have a parameter of type 'void *' because that is the set_params function pointer prototype. Make the function pointer protoype match the definitions so that there is no more violation.
Cc: stable@vger.kernel.org
Why does this matter for stable kernels, given that CFI is not in any kernel tree yet?
thanks,
greg k-h