[ 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 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/block/floppy.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
--- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3384,6 +3384,20 @@ static int fd_getgeo(struct block_device 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) { @@ -3510,6 +3524,8 @@ static int fd_locked_ioctl(struct block_ 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: @@ -3707,6 +3723,8 @@ 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;