Commit acf80219 authored by Denis Efremov's avatar Denis Efremov Committed by Greg Kroah-Hartman

floppy: fix out-of-bounds read in next_valid_format

[ Upstream commit 5635f897 ]

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: default avatarDenis Efremov <efremov@ispras.ru>
Tested-by: default avatarWilly Tarreau <w@1wt.eu>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent a2bd7b41
...@@ -3379,6 +3379,20 @@ static int fd_getgeo(struct block_device *bdev, struct hd_geometry *geo) ...@@ -3379,6 +3379,20 @@ static int fd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
return 0; 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, static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd,
unsigned long param) unsigned long param)
{ {
...@@ -3505,6 +3519,8 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode, unsigned int ...@@ -3505,6 +3519,8 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode, unsigned int
SUPBOUND(size, strlen((const char *)outparam) + 1); SUPBOUND(size, strlen((const char *)outparam) + 1);
break; break;
case FDSETDRVPRM: case FDSETDRVPRM:
if (!valid_floppy_drive_params(inparam.dp.autodetect))
return -EINVAL;
*UDP = inparam.dp; *UDP = inparam.dp;
break; break;
case FDGETDRVPRM: case FDGETDRVPRM:
...@@ -3702,6 +3718,8 @@ static int compat_setdrvprm(int drive, ...@@ -3702,6 +3718,8 @@ static int compat_setdrvprm(int drive,
return -EPERM; return -EPERM;
if (copy_from_user(&v, arg, sizeof(struct compat_floppy_drive_params))) if (copy_from_user(&v, arg, sizeof(struct compat_floppy_drive_params)))
return -EFAULT; return -EFAULT;
if (!valid_floppy_drive_params(v.autodetect))
return -EINVAL;
mutex_lock(&floppy_mutex); mutex_lock(&floppy_mutex);
UDP->cmos = v.cmos; UDP->cmos = v.cmos;
UDP->max_dtr = v.max_dtr; UDP->max_dtr = v.max_dtr;
......
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