[Cluster-devel] [PATCH] gfs2: fix slab corruption during mounting and umounting gfs file system

[Bob Peterson]

----- Original Message -----
| 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 corrruption.
| 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 mounting and to free memory
| during unmounting. 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 be happened.
| 
| 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 introduce the double free issue is
| commit 57c7310b8eb9 ("GFS2: use kmalloc for lvb bitmap")
| 
| Signed-off-by: Thomas Tai <thomas.tai at oracle.com>
| Reviewed-by: Liam R. Howlett <Liam.Howlett at Oracle.com>
| ---
Hi,

Thanks. This is now pushed to the for-next branch of the linux-gfs2 tree:
https://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2.git/commit/fs/gfs2?h=for-next&id=cc1dfa8b7571ea16dec9a29e0f4c4cad90b2a761

Please note that I fixed up the grammar a bit in your patch description.

Regards,

Bob Peterson
Red Hat File Systems