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| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2015-11-19 14:02:19 +0100 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2015-11-19 18:15:09 +0100 |
| commit | be821fd8e62765de43cc4f0e2db363d0e30a7e9b (patch) | |
| tree | 8704ba197c5f6267c0ba1b379d4e33121d5d1d6d /drivers | |
| parent | st: fix potential null pointer dereference. (diff) | |
| download | linux-be821fd8e62765de43cc4f0e2db363d0e30a7e9b.tar.xz linux-be821fd8e62765de43cc4f0e2db363d0e30a7e9b.zip | |
scsi_sysfs: protect against double execution of __scsi_remove_device()
On some host errors storvsc module tries to remove sdev by scheduling a job
which does the following:
sdev = scsi_device_lookup(wrk->host, 0, 0, wrk->lun);
if (sdev) {
scsi_remove_device(sdev);
scsi_device_put(sdev);
}
While this code seems correct the following crash is observed:
general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC
RIP: 0010:[<ffffffff81169979>] [<ffffffff81169979>] bdi_destroy+0x39/0x220
...
[<ffffffff814aecdc>] ? _raw_spin_unlock_irq+0x2c/0x40
[<ffffffff8127b7db>] blk_cleanup_queue+0x17b/0x270
[<ffffffffa00b54c4>] __scsi_remove_device+0x54/0xd0 [scsi_mod]
[<ffffffffa00b556b>] scsi_remove_device+0x2b/0x40 [scsi_mod]
[<ffffffffa00ec47d>] storvsc_remove_lun+0x3d/0x60 [hv_storvsc]
[<ffffffff81080791>] process_one_work+0x1b1/0x530
...
The problem comes with the fact that many such jobs (for the same device)
are being scheduled simultaneously. While scsi_remove_device() uses
shost->scan_mutex and scsi_device_lookup() will fail for a device in
SDEV_DEL state there is no protection against someone who did
scsi_device_lookup() before we actually entered __scsi_remove_device(). So
the whole scenario looks like that: two callers do simultaneous (or
preemption happens) calls to scsi_device_lookup() ant these calls succeed
for both of them, after that they try doing scsi_remove_device().
shost->scan_mutex only serializes their calls to __scsi_remove_device()
and we end up doing the cleanup path twice.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/scsi/scsi_sysfs.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 8b7fa8aece66..ed9182899f76 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -1100,6 +1100,14 @@ void __scsi_remove_device(struct scsi_device *sdev) { struct device *dev = &sdev->sdev_gendev; + /* + * This cleanup path is not reentrant and while it is impossible + * to get a new reference with scsi_device_get() someone can still + * hold a previously acquired one. + */ + if (sdev->sdev_state == SDEV_DEL) + return; + if (sdev->is_visible) { if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0) return; |