Commit cc1dfa8b authored Aug 15, 2017 by Thomas Tai Committed by Bob Peterson Aug 15, 2017

gfs2: fix slab corruption during mounting and umounting gfs file system



When using cman-3.0.12.1 and gfs2-utils-3.0.12.1, mounting and
unmounting GFS2 file system would cause kernel to hang. The slab
allocator suggests that it is likely a double free memory corruption.
The issue is traced back to v3.9-rc6 where a patch is submitted to
use kzalloc() for storing a bitmap instead of using a local variable.
The intention is to allocate memory during mount and to free memory
during unmount. The original patch misses a code path which has
already freed the memory and caused memory corruption. This patch sets
the memory pointer to NULL after the memory is freed, so that double
free memory corruption will not happen.

gdlm_mount()
  '-- set_recover_size() which use kzalloc()
  '-- if dlm does not support ops callbacks then
          '--- free_recover_size() which use kfree()

gldm_unmount()
  '-- free_recover_size() which use kfree()

Previous patch which introduced the double free issue is
commit 57c7310b ("GFS2: use kmalloc for lvb bitmap")

Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>

parent b066a4ee

fs/gfs2/lock_dlm.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1059,6 +1059,7 @@ static void free_recover_size(struct lm_lockstruct *ls)
		ls->ls_recover_submit = NULL;
		ls->ls_recover_result = NULL;
		ls->ls_recover_size = 0;
		ls->ls_lvb_bits = NULL;
		}

		/* dlm calls before it does lock recovery */

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