3.16.72-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Denis Efremov <efremov@xxxxxxxxx> commit 9b04609b784027968348796a18f601aed9db3789 upstream. This fixes the invalid pointer dereference in the drive_name function of the floppy driver. The native_format field of the struct floppy_drive_params is used as floppy_type array index in the drive_name function. Thus, the field should be checked the same way as the autodetect field. To trigger the bug, one could use a value out of range and set the drive parameters with the FDSETDRVPRM ioctl. Next, FDGETDRVTYP ioctl should be used to call the drive_name. A floppy disk is not required to be inserted. CAP_SYS_ADMIN is required to call FDSETDRVPRM. The patch adds the check for a value of the native_format field to be in the '0 <= x < ARRAY_SIZE(floppy_type)' range of the floppy_type array indices. The bug was found by syzkaller. Signed-off-by: Denis Efremov <efremov@xxxxxxxxx> Tested-by: Willy Tarreau <w@xxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> [bwh: Backported to 3.16: Drop changes in compat_setdrvprm(), as compat ioctls go via fd_ioctl_locked() after translation in compat_ioctl.c.] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3383,7 +3383,8 @@ static int fd_getgeo(struct block_device return 0; } -static bool valid_floppy_drive_params(const short autodetect[8]) +static bool valid_floppy_drive_params(const short autodetect[8], + int native_format) { size_t floppy_type_size = ARRAY_SIZE(floppy_type); size_t i = 0; @@ -3394,6 +3395,9 @@ static bool valid_floppy_drive_params(co return false; } + if (native_format < 0 || native_format >= floppy_type_size) + return false; + return true; } @@ -3523,7 +3527,8 @@ static int fd_locked_ioctl(struct block_ SUPBOUND(size, strlen((const char *)outparam) + 1); break; case FDSETDRVPRM: - if (!valid_floppy_drive_params(inparam.dp.autodetect)) + if (!valid_floppy_drive_params(inparam.dp.autodetect, + inparam.dp.native_format)) return -EINVAL; *UDP = inparam.dp; break;