compat_ioct: fix bsg SG_IO

84eb8fb42c120 "[SCSI] compat_ioct: fix bsg SG_IO" introduces an uninitialized variable use.

   278  static int sg_ioctl_trans(unsigned int fd, unsigned int cmd,
   279                          sg_io_hdr32_t __user *sgio32)
   280  {
   281          sg_io_hdr_t __user *sgio;
   282          u16 iovec_count;
   283          u32 data;
   284          void __user *dxferp;
   285          int err;
   286          int interface_id;
   287  
   288          if (get_user(interface_id, &sgio32->interface_id))
                                            ^^^^^^

sgio32 is unitialized here. Unfortunately Gcc doesn't warn about it.

Quoted 15 lines · Dan Carpenter

84eb8fb42c120 "[SCSI] compat_ioct: fix bsg SG_IO" introduces an uninitialized variable use.

   278  static int sg_ioctl_trans(unsigned int fd, unsigned int cmd,
   279                          sg_io_hdr32_t __user *sgio32)
   280  {
   281          sg_io_hdr_t __user *sgio;
   282          u16 iovec_count;
   283          u32 data;
   284          void __user *dxferp;
   285          int err;
   286          int interface_id;
   287  
   288          if (get_user(interface_id, &sgio32->interface_id))
                                            ^^^^^^

Quoted 1 line

sgio32 is unitialized here. Unfortunately Gcc doesn't warn about it.

I don't quite understand what makes you think that: it's passed in as an argument to the function. It's a pointer to the userspace 32 bit representation of the structure. The use logic is a slightly convoluted way of saying we only understand the 'S' header but we're going to let the real ioctl routine say what the error is if it's not type 'S'.