On Wed, Dec 18, 2019 at 1:56 AM Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > > Hmm, this is a surprising bug. syzbot provided a C reproducer, but the definition > of "struct serial_struct" used in that reproducer is wrong. As a result, syzbot was > reporting crash caused by passing wrong arguments. ;-) We are on it: https://github.com/google/syzkaller/blob/master/sys/linux/dev_ptmx.txt.warn#L20-L25 > close_delay field used in the C reproducer is sizeof(unsigned int) bytes rather than > sizeof(unsigned short) bytes, thus fields after close_delay field are incorrectly > interpreted. > > ---------------------------------------- > #include <stdio.h> > #include <sys/types.h> > #include <sys/stat.h> > #include <fcntl.h> > #include <sys/ioctl.h> > #include <linux/serial.h> > > struct bad_serial_struct { > int type; > int line; > unsigned int port; > int irq; > int flags; > int xmit_fifo_size; > int custom_divisor; > int baud_base; > unsigned int close_delay; /* Correct type is "unsigned short". */ > char io_type; > char reserved_char[1]; > int hub6; > unsigned short closing_wait; > unsigned short closing_wait2; > unsigned char *iomem_base; > unsigned short iomem_reg_shift; > unsigned int port_high; > unsigned long iomap_base; > }; > > int main(int argc, char *argv[]) > { > struct bad_serial_struct ss = { }; > int fd = open("/dev/ttyS3", O_RDONLY); > ss.type = 0xa; > ss.line = 0x400000; > ss.port = 0x100; > ss.irq = 0; > ss.flags = 0x400000; > ss.xmit_fifo_size = 0; > ss.custom_divisor = 0; > ss.baud_base = 0x80000; > ss.close_delay = 0x200ff; > ss.io_type = 0; > ss.reserved_char[0] = 0x41; > ss.hub6 = 3; > ss.closing_wait = 0; > ss.closing_wait2 = 0x7c5; > ss.iomem_base = NULL; > ss.iomem_reg_shift = 0; > ss.port_high = 0; > ss.iomap_base = 0; > ioctl(fd, TIOCSSERIAL, &ss); > return 0; > } > ----------------------------------------
