Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.15 01/33] floppy: disable FDRAWCMD by default | Date | Fri, 29 Apr 2022 12:41:48 +0200 |
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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_ULNCpsCVE5s8ZeBQgQ@mail.gmail.com Link: https://lore.kernel.org/all/CAEAjamu1FRhz6StCe_55XY5s389ZP_xmCF69k987En+1z53=eg@mail.gmail.com 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 @@ -33,6 +33,22 @@ 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 @@ -2984,6 +2984,8 @@ static const char *drive_name(int type, return "(null)"; } +#ifdef CONFIG_BLK_DEV_FD_RAWCMD + /* raw commands */ static void raw_cmd_done(int flag) { @@ -3183,6 +3185,35 @@ 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 */ @@ -3371,7 +3402,6 @@ static int fd_locked_ioctl(struct block_ { int drive = (long)bdev->bd_disk->private_data; int type = ITYPE(drive_state[drive].fd_device); - int i; int ret; int size; union inparam { @@ -3522,16 +3552,7 @@ static int fd_locked_ioctl(struct block_ outparam = &write_errors[drive]; 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;
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