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Message-Id: <20210315135208.569811301@linuxfoundation.org>
Date: Mon, 15 Mar 2021 14:51:23 +0100
From: gregkh@...uxfoundation.org
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
Jiri Kosina <jkosina@...e.cz>,
Wade Mealing <wmealing@...hat.com>
Subject: [PATCH 4.4 09/75] floppy: fix lock_fdc() signal handling
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
From: Jiri Kosina <jkosina@...e.cz>
commit a0c80efe5956ccce9fe7ae5c78542578c07bc20a upstream.
floppy_revalidate() doesn't perform any error handling on lock_fdc()
result. lock_fdc() might actually be interrupted by a signal (it waits for
fdc becoming non-busy interruptibly). In such case, floppy_revalidate()
proceeds as if it had claimed the lock, but it fact it doesn't.
In case of multiple threads trying to open("/dev/fdX"), this leads to
serious corruptions all over the place, because all of a sudden there is
no critical section protection (that'd otherwise be guaranteed by locked
fd) whatsoever.
While at this, fix the fact that the 'interruptible' parameter to
lock_fdc() doesn't make any sense whatsoever, because we always wait
interruptibly anyway.
Most of the lock_fdc() callsites do properly handle error (and propagate
EINTR), but floppy_revalidate() and floppy_check_events() don't. Fix this.
Spotted by 'syzkaller' tool.
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Tested-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Cc: Wade Mealing <wmealing@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
drivers/block/floppy.c | 35 +++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -870,7 +870,7 @@ static void set_fdc(int drive)
}
/* locks the driver */
-static int lock_fdc(int drive, bool interruptible)
+static int lock_fdc(int drive)
{
if (WARN(atomic_read(&usage_count) == 0,
"Trying to lock fdc while usage count=0\n"))
@@ -2180,7 +2180,7 @@ static int do_format(int drive, struct f
{
int ret;
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
set_floppy(drive);
@@ -2967,7 +2967,7 @@ static int user_reset_fdc(int drive, int
{
int ret;
- if (lock_fdc(drive, interruptible))
+ if (lock_fdc(drive))
return -EINTR;
if (arg == FD_RESET_ALWAYS)
@@ -3254,7 +3254,7 @@ static int set_geometry(unsigned int cmd
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
mutex_lock(&open_lock);
- if (lock_fdc(drive, true)) {
+ if (lock_fdc(drive)) {
mutex_unlock(&open_lock);
return -EINTR;
}
@@ -3274,7 +3274,7 @@ static int set_geometry(unsigned int cmd
} else {
int oldStretch;
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
if (cmd != FDDEFPRM) {
/* notice a disk change immediately, else
@@ -3360,7 +3360,7 @@ static int get_floppy_geometry(int drive
if (type)
*g = &floppy_type[type];
else {
- if (lock_fdc(drive, false))
+ if (lock_fdc(drive))
return -EINTR;
if (poll_drive(false, 0) == -EINTR)
return -EINTR;
@@ -3462,7 +3462,7 @@ static int fd_locked_ioctl(struct block_
if (UDRS->fd_ref != 1)
/* somebody else has this drive open */
return -EBUSY;
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
/* do the actual eject. Fails on
@@ -3474,7 +3474,7 @@ static int fd_locked_ioctl(struct block_
process_fd_request();
return ret;
case FDCLRPRM:
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
current_type[drive] = NULL;
floppy_sizes[drive] = MAX_DISK_SIZE << 1;
@@ -3499,7 +3499,7 @@ static int fd_locked_ioctl(struct block_
UDP->flags &= ~FTD_MSG;
return 0;
case FDFMTBEG:
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
if (poll_drive(true, FD_RAW_NEED_DISK) == -EINTR)
return -EINTR;
@@ -3516,7 +3516,7 @@ static int fd_locked_ioctl(struct block_
return do_format(drive, &inparam.f);
case FDFMTEND:
case FDFLUSH:
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
return invalidate_drive(bdev);
case FDSETEMSGTRESH:
@@ -3542,7 +3542,7 @@ static int fd_locked_ioctl(struct block_
outparam = UDP;
break;
case FDPOLLDRVSTAT:
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
if (poll_drive(true, FD_RAW_NEED_DISK) == -EINTR)
return -EINTR;
@@ -3565,7 +3565,7 @@ static int fd_locked_ioctl(struct block_
case FDRAWCMD:
if (type)
return -EINVAL;
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
set_floppy(drive);
i = raw_cmd_ioctl(cmd, (void __user *)param);
@@ -3574,7 +3574,7 @@ static int fd_locked_ioctl(struct block_
process_fd_request();
return i;
case FDTWADDLE:
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
return -EINTR;
twaddle();
process_fd_request();
@@ -3801,7 +3801,7 @@ static int compat_getdrvstat(int drive,
mutex_lock(&floppy_mutex);
if (poll) {
- if (lock_fdc(drive, true))
+ if (lock_fdc(drive))
goto Eintr;
if (poll_drive(true, FD_RAW_NEED_DISK) == -EINTR)
goto Eintr;
@@ -4109,7 +4109,8 @@ static unsigned int floppy_check_events(
return DISK_EVENT_MEDIA_CHANGE;
if (time_after(jiffies, UDRS->last_checked + UDP->checkfreq)) {
- lock_fdc(drive, false);
+ if (lock_fdc(drive))
+ return -EINTR;
poll_drive(false, 0);
process_fd_request();
}
@@ -4208,7 +4209,9 @@ static int floppy_revalidate(struct gend
"VFS: revalidate called on non-open device.\n"))
return -EFAULT;
- lock_fdc(drive, false);
+ res = lock_fdc(drive);
+ if (res)
+ return res;
cf = (test_bit(FD_DISK_CHANGED_BIT, &UDRS->flags) ||
test_bit(FD_VERIFY_BIT, &UDRS->flags));
if (!(cf || test_bit(drive, &fake_change) || drive_no_geom(drive))) {
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