floppy: fix out-of-bounds read in next_valid_format (5635f897) · Commits · 戴 / test

This fixes a global out-of-bounds read access in the next_valid_format function of the floppy driver. The values from autodetect field of the struct floppy_drive_params are used as indices for the floppy_type array in the next_valid_format function 'floppy_type[DP->autodetect[probed_format]].sect'. To trigger the bug, one could use a value out of range and set the drive parameters with the FDSETDRVPRM ioctl. A floppy disk is not required to be inserted. CAP_SYS_ADMIN is required to call FDSETDRVPRM. The patch adds the check for values of the autodetect 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

+18 −0

Original line number	Diff line number	Diff line
		@@ -3380,6 +3380,20 @@ static int fd_getgeo(struct block_device bdev, struct hd_geometry geo)
		return 0;
		}

		static bool valid_floppy_drive_params(const short autodetect[8])
		{
		size_t floppy_type_size = ARRAY_SIZE(floppy_type);
		size_t i = 0;

		for (i = 0; i < 8; ++i) {
		if (autodetect[i] < 0 \|\|
		autodetect[i] >= floppy_type_size)
		return false;
		}

		return true;
		}

		static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd,
		unsigned long param)
		{
		@@ -3506,6 +3520,8 @@ 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))
		return -EINVAL;
		*UDP = inparam.dp;
		break;
		case FDGETDRVPRM:
		@@ -3703,6 +3719,8 @@ 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))
		return -EINVAL;
		mutex_lock(&floppy_mutex);
		UDP->cmos = v.cmos;
		UDP->max_dtr = v.max_dtr;

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