floppy: fix invalid pointer dereference in drive_name (9b04609b) · Commits · 戴 / test

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@ispras.ru> Tested-by:

Willy Tarreau <w@1wt.eu> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/floppy.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -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;

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