From: Willy Tarreau w@1wt.eu
commit 233087ca063686964a53c829d547c7571e3f67bf upstream.
Minh Yuan reported a concurrency use-after-free issue in the floppy code between raw_cmd_ioctl and seek_interrupt.
[ It turns out this has been around, and that others have reported the KASAN splats over the years, but Minh Yuan had a reproducer for it and so gets primary credit for reporting it for this fix - Linus ]
The problem is, this driver tends to break very easily and nowadays, nobody is expected to use FDRAWCMD anyway since it was used to manipulate non-standard formats. The risk of breaking the driver is higher than the risk presented by this race, and accessing the device requires privileges anyway.
Let's just add a config option to completely disable this ioctl and leave it disabled by default. Distros shouldn't use it, and only those running on antique hardware might need to enable it.
Link: https://lore.kernel.org/all/000000000000b71cdd05d703f6bf@google.com/ Link: https://lore.kernel.org/lkml/CAKcFiNC=MfYVW-Jt9A3=FPJpTwCD2PL_ULNCpsCVE5s8Ze... Link: https://lore.kernel.org/all/CAEAjamu1FRhz6StCe_55XY5s389ZP_xmCF69k987En+1z53... Reported-by: Minh Yuan yuanmingbuaa@gmail.com Reported-by: syzbot+8e8958586909d62b6840@syzkaller.appspotmail.com Reported-by: cruise k cruise4k@gmail.com Reported-by: Kyungtae Kim kt0755@gmail.com Suggested-by: Linus Torvalds torvalds@linuxfoundation.org Tested-by: Denis Efremov efremov@linux.com Signed-off-by: Willy Tarreau w@1wt.eu Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/block/Kconfig | 16 ++++++++++++++++ drivers/block/floppy.c | 43 ++++++++++++++++++++++++++++++++----------- 2 files changed, 48 insertions(+), 11 deletions(-)
--- a/drivers/block/Kconfig +++ b/drivers/block/Kconfig @@ -35,6 +35,22 @@ config BLK_DEV_FD To compile this driver as a module, choose M here: the module will be called floppy.
+config BLK_DEV_FD_RAWCMD + bool "Support for raw floppy disk commands (DEPRECATED)" + depends on BLK_DEV_FD + help + If you want to use actual physical floppies and expect to do + special low-level hardware accesses to them (access and use + non-standard formats, for example), then enable this. + + Note that the code enabled by this option is rarely used and + might be unstable or insecure, and distros should not enable it. + + Note: FDRAWCMD is deprecated and will be removed from the kernel + in the near future. + + If unsure, say N. + config AMIGA_FLOPPY tristate "Amiga floppy support" depends on AMIGA --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3018,6 +3018,8 @@ static const char *drive_name(int type, return "(null)"; }
+#ifdef CONFIG_BLK_DEV_FD_RAWCMD + /* raw commands */ static void raw_cmd_done(int flag) { @@ -3229,6 +3231,35 @@ static int raw_cmd_ioctl(int cmd, void _ return ret; }
+static int floppy_raw_cmd_ioctl(int type, int drive, int cmd, + void __user *param) +{ + int ret; + + pr_warn_once("Note: FDRAWCMD is deprecated and will be removed from the kernel in the near future.\n"); + + if (type) + return -EINVAL; + if (lock_fdc(drive)) + return -EINTR; + set_floppy(drive); + ret = raw_cmd_ioctl(cmd, param); + if (ret == -EINTR) + return -EINTR; + process_fd_request(); + return ret; +} + +#else /* CONFIG_BLK_DEV_FD_RAWCMD */ + +static int floppy_raw_cmd_ioctl(int type, int drive, int cmd, + void __user *param) +{ + return -EOPNOTSUPP; +} + +#endif + static int invalidate_drive(struct block_device *bdev) { /* invalidate the buffer track to force a reread */ @@ -3416,7 +3447,6 @@ static int fd_locked_ioctl(struct block_ { int drive = (long)bdev->bd_disk->private_data; int type = ITYPE(UDRS->fd_device); - int i; int ret; int size; union inparam { @@ -3567,16 +3597,7 @@ static int fd_locked_ioctl(struct block_ outparam = UDRWE; break; case FDRAWCMD: - if (type) - return -EINVAL; - if (lock_fdc(drive)) - return -EINTR; - set_floppy(drive); - i = raw_cmd_ioctl(cmd, (void __user *)param); - if (i == -EINTR) - return -EINTR; - process_fd_request(); - return i; + return floppy_raw_cmd_ioctl(type, drive, cmd, (void __user *)param); case FDTWADDLE: if (lock_fdc(drive)) return -EINTR;