[ Upstream commit 9b04609b784027968348796a18f601aed9db3789 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 77c527db5134..8b443ee1d005 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3379,7 +3379,8 @@ 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; @@ -3390,6 +3391,9 @@ 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; }
@@ -3519,7 +3523,8 @@ 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; @@ -3718,7 +3723,7 @@ 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;