From 605a9259a3458bfa583d73ed698236ec052a1c01 Mon Sep 17 00:00:00 2001 From: Denis Efremov Date: Fri, 12 Jul 2019 21:55:22 +0300 Subject: [PATCH] floppy: fix invalid pointer dereference in drive_name 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 Tested-by: Willy Tarreau Signed-off-by: Linus Torvalds --- drivers/block/floppy.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index b70d6e103a570..671a0ae434b43 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3380,7 +3380,8 @@ static int fd_getgeo(struct block_device *bdev, struct hd_geometry *geo) 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; @@ -3391,6 +3392,9 @@ static bool valid_floppy_drive_params(const short autodetect[8]) return false; } + if (native_format < 0 || native_format >= floppy_type_size) + return false; + return true; } @@ -3520,7 +3524,8 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode, unsigned int 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; @@ -3719,7 +3724,7 @@ static int compat_setdrvprm(int drive, return -EPERM; if (copy_from_user(&v, arg, sizeof(struct compat_floppy_drive_params))) return -EFAULT; - if (!valid_floppy_drive_params(v.autodetect)) + if (!valid_floppy_drive_params(v.autodetect, v.native_format)) return -EINVAL; mutex_lock(&floppy_mutex); UDP->cmos = v.cmos; -- 2.39.5