[ Upstream commit 5635f897ed83fd539df78e98ba69ee91592f9bb8 ]
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 <efre...@ispras.ru>
Tested-by: Willy Tarreau <w...@1wt.eu>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
drivers/block/floppy.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index e2f742e17683..77c527db5134 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3379,6 +3379,20 @@ 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)
{
@@ -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);
break;
case FDSETDRVPRM:
+ if (!valid_floppy_drive_params(inparam.dp.autodetect))
+ return -EINVAL;
*UDP = inparam.dp;
break;
case FDGETDRVPRM:
@@ -3702,6 +3718,8 @@ 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;
--
2.20.1
