Prevent memory scribble by checking that ioctl buffer size parameters are sane. Without this check, on 32 bits system, if .insize = 0xffffffff - 20 and .outsize the amount to scribble, we would overflow, allocate a small amounts and be able to write outside of the malloc'ed area. Adding a hard limit allows argument checking of the ioctl. With the current EC, it is expected .insize and .outsize to be at around 512 bytes or less.
Signed-off-by: Gwendal Grignou <[email protected]> --- drivers/platform/chrome/cros_ec_dev.c | 4 ++++ drivers/platform/chrome/cros_ec_proto.c | 4 ++-- include/linux/mfd/cros_ec.h | 6 ++++-- 3 files changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c index d45cd25..187470c 100644 --- a/drivers/platform/chrome/cros_ec_dev.c +++ b/drivers/platform/chrome/cros_ec_dev.c @@ -137,6 +137,10 @@ static long ec_device_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg) if (copy_from_user(&u_cmd, arg, sizeof(u_cmd))) return -EFAULT; + if ((u_cmd.outsize > EC_MAX_MSG_BYTES) || + (u_cmd.insize > EC_MAX_MSG_BYTES)) + return -EINVAL; + s_cmd = kmalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize), GFP_KERNEL); if (!s_cmd) diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c index 990308c..b6e161f 100644 --- a/drivers/platform/chrome/cros_ec_proto.c +++ b/drivers/platform/chrome/cros_ec_proto.c @@ -298,8 +298,8 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev) ec_dev->max_response = EC_PROTO2_MAX_PARAM_SIZE; ec_dev->max_passthru = 0; ec_dev->pkt_xfer = NULL; - ec_dev->din_size = EC_MSG_BYTES; - ec_dev->dout_size = EC_MSG_BYTES; + ec_dev->din_size = EC_PROTO2_MSG_BYTES; + ec_dev->dout_size = EC_PROTO2_MSG_BYTES; } else { /* * It's possible for a test to occur too early when diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h index 494682c..9cb77ed 100644 --- a/include/linux/mfd/cros_ec.h +++ b/include/linux/mfd/cros_ec.h @@ -50,9 +50,11 @@ enum { EC_MSG_TX_TRAILER_BYTES, EC_MSG_RX_PROTO_BYTES = 3, - /* Max length of messages */ - EC_MSG_BYTES = EC_PROTO2_MAX_PARAM_SIZE + + /* Max length of messages for proto 2*/ + EC_PROTO2_MSG_BYTES = EC_PROTO2_MAX_PARAM_SIZE + EC_MSG_TX_PROTO_BYTES, + + EC_MAX_MSG_BYTES = 64 * 1024, }; /* -- 2.7.0.rc3.207.g0ac5344
