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scsi: sr: Fix unintentional arithmetic wraparound 

Running syzkaller with the newly reintroduced signed integer overflow
sanitizer produces this report:

[   65.194362] ------------[ cut here ]------------
[   65.197752] UBSAN: signed-integer-overflow in ../drivers/scsi/sr_ioctl.c:436:9
[   65.203607] -2147483648 * 177 cannot be represented in type 'int'
[   65.207911] CPU: 2 PID: 10416 Comm: syz-executor.1 Not tainted 6.8.0-rc2-00035-gb3ef86b5a957 #1
[   65.213585] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   65.219923] Call Trace:
[   65.221556]  <TASK>
[   65.223029]  dump_stack_lvl+0x93/0xd0
[   65.225573]  handle_overflow+0x171/0x1b0
[   65.228219]  sr_select_speed+0xeb/0xf0
[   65.230786]  ? __pm_runtime_resume+0xe6/0x130
[   65.233606]  sr_block_ioctl+0x15d/0x1d0
...

Historically, the signed integer overflow sanitizer did not work in the
kernel due to its interaction with `-fwrapv` but this has since been
changed [1] in the newest version of Clang. It was re-enabled in the kernel
with Commit 557f8c582a ("ubsan: Reintroduce signed overflow sanitizer").

Firstly, let's change the type of "speed" to unsigned long as
sr_select_speed()'s only caller passes in an unsigned long anyways.

$ git grep '\.select_speed'
|	drivers/scsi/sr.c:      .select_speed           = sr_select_speed,
...
|	static int cdrom_ioctl_select_speed(struct cdrom_device_info *cdi,
|	                unsigned long arg)
|	{
|	        ...
|	        return cdi->ops->select_speed(cdi, arg);
|	}

Next, let's add an extra check to make sure we don't exceed 0xffff/177
(350) since 0xffff is the max speed. This has two benefits: 1) we deal
with integer overflow before it happens and 2) we properly respect the
max speed of 0xffff. There are some "magic" numbers here but I did not
want to change more than what was necessary.

Link: https://github.com/llvm/llvm-project/pull/82432 [1]
Closes: https://github.com/KSPP/linux/issues/357
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240508-b4-b4-sio-sr_select_speed-v2-1-00b68f724290@google.com
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Justin Stitt 2024-05-08 17:22:51 +00:00 committed by Martin K. Petersen
parent 10157b1fc1
commit 9fad9d560a
4 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/cdrom/cdrom-standard.rst
View File

@ -217,7 +217,7 @@ current *struct* is::
int (*media_changed)(struct cdrom_device_info *, int);
int (*tray_move)(struct cdrom_device_info *, int);
int (*lock_door)(struct cdrom_device_info *, int);
int (*select_speed)(struct cdrom_device_info *, int);
int (*select_speed)(struct cdrom_device_info *, unsigned long);
int (*get_last_session) (struct cdrom_device_info *,
struct cdrom_multisession *);
int (*get_mcn)(struct cdrom_device_info *, struct cdrom_mcn *);
@ -396,7 +396,7 @@ action need be taken, and the return value should be 0.
::
int select_speed(struct cdrom_device_info *cdi, int speed)
int select_speed(struct cdrom_device_info *cdi, unsigned long speed)
Some CD-ROM drives are capable of changing their head-speed. There
are several reasons for changing the speed of a CD-ROM drive. Badly

2
drivers/scsi/sr.h
View File

@ -65,7 +65,7 @@ int sr_disk_status(struct cdrom_device_info *);
int sr_get_last_session(struct cdrom_device_info *, struct cdrom_multisession *);
int sr_get_mcn(struct cdrom_device_info *, struct cdrom_mcn *);
int sr_reset(struct cdrom_device_info *);
int sr_select_speed(struct cdrom_device_info *cdi, int speed);
int sr_select_speed(struct cdrom_device_info *cdi, unsigned long speed);
int sr_audio_ioctl(struct cdrom_device_info *, unsigned int, void *);
int sr_is_xa(Scsi_CD *);

5
drivers/scsi/sr_ioctl.c
View File

@ -425,11 +425,14 @@ int sr_reset(struct cdrom_device_info *cdi)
return 0;
}
int sr_select_speed(struct cdrom_device_info *cdi, int speed)
int sr_select_speed(struct cdrom_device_info *cdi, unsigned long speed)
{
Scsi_CD *cd = cdi->handle;
struct packet_command cgc;
/* avoid exceeding the max speed or overflowing integer bounds */
speed = clamp(0, speed, 0xffff / 177);
if (speed == 0)
speed = 0xffff; /* set to max */
else

2
include/linux/cdrom.h
View File

@ -77,7 +77,7 @@ struct cdrom_device_ops {
unsigned int clearing, int slot);
int (*tray_move) (struct cdrom_device_info *, int);
int (*lock_door) (struct cdrom_device_info *, int);
int (*select_speed) (struct cdrom_device_info *, int);
int (*select_speed) (struct cdrom_device_info *, unsigned long);
int (*get_last_session) (struct cdrom_device_info *,
struct cdrom_multisession *);
int (*get_mcn) (struct cdrom_device_info *,