Hi, I've looked into this issue found by Syzbot and I made a patch: https://syzkaller.appspot.com/bug?id=d03abd8b42847f7f69b1d1d7f97208ae425b1163 The autofs subsystem does not check that the "path" parameter is present within the "param" struct passed by the userspace in case the AUTOFS_DEV_IOCTL_OPENMOUNT_CMD command is passed. Indeed, it assumes a path is always provided (though a path is not always present, as per how the struct is defined: https://github.com/torvalds/linux/blob/master/include/uapi/linux/auto_dev-ioctl.h#L89). Skipping the check provokes an oob read in "strlen", called by "getname_kernel", in turn called by the autofs to assess the length of the non-existing path. To solve it, modify the "validate_dev_ioctl" function to check also that a path has been provided if the command is AUTOFS_DEV_IOCTL_OPENMOUNT_CMD. --- b/fs/autofs/dev-ioctl.c 2018-07-01 23:10:16.059728621 +0200 +++ a/fs/autofs/dev-ioctl.c 2018-07-01 23:10:24.311792133 +0200 @@ -136,6 +136,9 @@ static int validate_dev_ioctl(int cmd, s goto out; } } + /* AUTOFS_DEV_IOCTL_OPENMOUNT_CMD without path */ + else if(_IOC_NR(cmd) == AUTOFS_DEV_IOCTL_OPENMOUNT_CMD) + return -EINVAL; err = 0; out: Tested and solves the issue on Linus' main git tree. Tomas -- To unsubscribe from this list: send the line "unsubscribe autofs" in
