-stable review patch. If anyone has any objections, please let us know. --------------------- From: Alasdair G Kergon upstream commit: 570b9d968bf9b16974252ef7cbce73fa6dac34f3 upgrade_mode() sets bdev to NULL temporarily, and does not have any locking to exclude anything from seeing that NULL. In dm_table_any_congested() bdev_get_queue() can dereference that NULL and cause a reported oops. Fix this by not changing that field during the mode upgrade. Cc: stable@kernel.org Cc: Neil Brown Signed-off-by: Alasdair G Kergon Signed-off-by: Chris Wright --- drivers/md/dm-table.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -399,28 +399,30 @@ static int check_device_area(struct dm_d } /* - * This upgrades the mode on an already open dm_dev. Being + * This upgrades the mode on an already open dm_dev, being * careful to leave things as they were if we fail to reopen the - * device. + * device and not to touch the existing bdev field in case + * it is accessed concurrently inside dm_table_any_congested(). */ static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode, struct mapped_device *md) { int r; - struct dm_dev_internal dd_copy; - dev_t dev = dd->dm_dev.bdev->bd_dev; + struct dm_dev_internal dd_new, dd_old; - dd_copy = *dd; + dd_new = dd_old = *dd; + + dd_new.dm_dev.mode |= new_mode; + dd_new.dm_dev.bdev = NULL; + + r = open_dev(&dd_new, dd->dm_dev.bdev->bd_dev, md); + if (r) + return r; dd->dm_dev.mode |= new_mode; - dd->dm_dev.bdev = NULL; - r = open_dev(dd, dev, md); - if (!r) - close_dev(&dd_copy, md); - else - *dd = dd_copy; + close_dev(&dd_old, md); - return r; + return 0; } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/