[dm-devel] [PATCH] 2.6.12-rc6: fix __rh_alloc()/rh_update_states() race in dm-raid1.c

[Jun'ichi Nomura]

Hello,

the attached patch fixes the bug in dm-raid1.c that
the region returned by __rh_alloc() may be freed while
it's in use.

__rh_alloc() write-unlocks the hash_lock after inserting the new region.
Though it read-locks the hash-lock just after that, it's possible
that the region was reclaimed by rh_update_states() as the region
was clean at the time.

   CPU0                                  CPU1
   -----------------------------------------------------------------------
   __rh_alloc()
     write_lock(hash_lock)
     <insert new region to clean list>
     write_unlock(hash_lock)
                                         rh_update_states()
                                           write_lock(hash_lock)
                                           <move clean regions to freeable list>
                                           write_unlock(hash_lock)
                                           <free regions in the freeable list>
     read_lock(hash_lock)
     <return the region>

Signed-off-by: Jun'ichi Nomura <j-nomura at ce.jp.nec.com>

-------------- next part --------------
A non-text attachment was scrubbed...
Name: dm-raid1-race1.patch
Type: text/x-patch
Size: 370 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/dm-devel/attachments/20050616/207f7dd8/attachment.bin>