Hello,
This patch is to modify media_device_request_alloc() so that it can pass
CFI(Control Flow Integrity) check. I would like some review comments.
media_device_request_alloc() is saved in fn of media_ioctl_info struct,
which is defined as long (*fn)(struct media_device *dev, void *arg). The
type of the second parameter of media_device_request_alloc() is int* now,
but it is void* in fn of media_ioctl_info. We got some ABI violation here.
Therefore, we would like to use void* instead of int* for the second
parameter of media_device_request_alloc().
static long media_device_request_alloc(struct media_device *mdev,
int *alloc_fd);
struct media_ioctl_info {
unsigned int cmd;
unsigned short flags;
long (*fn)(struct media_device *dev, void *arg);
long (*arg_from_user)(void *karg, void __user *uarg, unsigned int cmd);
long (*arg_to_user)(void __user *uarg, void *karg, unsigned int cmd);
};
Here is an example. With Android’s CFI checking, we got the following error
without this change.
[ 23.502477] mtk-cam soc:camisp: sd:mtk-cam raw-0 pad:2 set format w/h/code 2328/1748/0x3007
[ 23.518690] Kernel panic - not syncing: CFI failure (target: media_device_request_alloc+0x0/0x4)
[ 23.519804] CPU: 7 PID: 818 Comm: mtkv4l2_ut Tainted: G S O 5.4.39-g02c0a4858bed-dirty #45
[ 23.521553] Call trace:
[ 23.521868] dump_backtrace.cfi_jt+0x0/0x4
[ 23.522389] dump_stack+0xb8/0x114
[ 23.522824] panic+0x170/0x3e0
[ 23.523215] __ubsan_handle_cfi_check_fail_abort+0x0/0x14
[ 23.523896] perf_proc_update_handler+0x0/0xcc
[ 23.524460] __cfi_check+0x610cc/0x68ef0
[ 23.524959] media_device_ioctl+0x218/0x238
[ 23.525488] media_device_compat_ioctl+0x60/0x7c
[ 23.526072] media_compat_ioctl+0x58/0x9c
[ 23.526581] __arm64_compat_sys_ioctl+0x10c/0x434
[ 23.527176] el0_svc_common+0xb4/0x18c
[ 23.527651] el0_svc_compat_handler+0x1c/0x28
[ 23.528202] el0_svc_compat+0x8/0x24
[ 23.528659] SMP: stopping secondary CPUs
[ 23.529161] Kernel Offset: 0x24b8c00000 from 0xffffffc010000000
[ 23.529906] PHYS_OFFSET: 0xffffffdd00000000
[ 23.530434] CPU features: 0x00000006,2a80a238
[ 23.530983] Memory Limit: none
PPL_LOG_STORE: check once, sig value 0x27, addr 0x116000.
==================
Changes in v2
==================
We also removed the type cast in the MEDIA_IOC_ARG define .
Frederic Chen (1):
media: mc-device.c: change media_device_request_alloc to match
media_ioctl_info
drivers/media/mc/mc-device.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
