@@ -2341,7 +2341,7 @@ int dm_setup_md_queue(struct mapped_device *md)
return 0;
}
-static struct mapped_device *dm_find_md(dev_t dev)
+struct mapped_device *dm_get_md(dev_t dev)
{
struct mapped_device *md;
unsigned minor = MINOR(dev);
@@ -2352,12 +2352,15 @@ static struct mapped_device *dm_find_md(dev_t dev)
spin_lock(&_minor_lock);
md = idr_find(&_minor_idr, minor);
- if (md && (md == MINOR_ALLOCED ||
- (MINOR(disk_devt(dm_disk(md))) != minor) ||
- dm_deleting_md(md) ||
- test_bit(DMF_FREEING, &md->flags))) {
- md = NULL;
- goto out;
+ if (md) {
+ if ((md == MINOR_ALLOCED ||
+ (MINOR(disk_devt(dm_disk(md))) != minor) ||
+ dm_deleting_md(md) ||
+ test_bit(DMF_FREEING, &md->flags))) {
+ md = NULL;
+ goto out;
+ }
+ dm_get(md);
}
out:
@@ -2365,16 +2368,6 @@ out:
return md;
}
-
-struct mapped_device *dm_get_md(dev_t dev)
-{
- struct mapped_device *md = dm_find_md(dev);
-
- if (md)
- dm_get(md);
-
- return md;
-}
EXPORT_SYMBOL_GPL(dm_get_md);
void *dm_get_mdptr(struct mapped_device *md)
This is a note to let you know that I have just added a patch titled dm: fix a race condition in dm_get_md to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt8. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From d11ee781901dc29ee7fcd5d00e8376f0f95eae35 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka@redhat.com> Date: Tue, 17 Feb 2015 14:30:53 -0500 Subject: dm: fix a race condition in dm_get_md commit 2bec1f4a8832e74ebbe859f176d8a9cb20dd97f4 upstream. The function dm_get_md finds a device mapper device with a given dev_t, increases the reference count and returns the pointer. dm_get_md calls dm_find_md, dm_find_md takes _minor_lock, finds the device, tests that the device doesn't have DMF_DELETING or DMF_FREEING flag, drops _minor_lock and returns pointer to the device. dm_get_md then calls dm_get. dm_get calls BUG if the device has the DMF_FREEING flag, otherwise it increments the reference count. There is a possible race condition - after dm_find_md exits and before dm_get is called, there are no locks held, so the device may disappear or DMF_FREEING flag may be set, which results in BUG. To fix this bug, we need to call dm_get while we hold _minor_lock. This patch renames dm_find_md to dm_get_md and changes it so that it calls dm_get while holding the lock. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/md/dm.c | 27 ++++++++++----------------- 1 file changed, 10 insertions(+), 17 deletions(-)