edac_mc: edac_mc_free() cannot assume mem_ctl_info is registered in sysfs.
authorShaun Ruffell <sruffell@digium.com>
Sun, 23 Sep 2012 01:26:38 +0000 (20:26 -0500)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sun, 23 Sep 2012 21:46:40 +0000 (14:46 -0700)
commitfaa2ad09c01c48012fe4c117d3256e354e0f9238
treeb525fbdc4fa81daec86c6b09de4ee48f009d1934
parentef6e7816b4546475d04b4ea22d58c48472157c70
edac_mc: edac_mc_free() cannot assume mem_ctl_info is registered in sysfs.

Fix potential NULL pointer dereference in edac_unregister_sysfs() on
system boot introduced in 3.6-rc1.

Since commit 7a623c039 ("edac: rewrite the sysfs code to use struct
device") edac_mc_alloc() no longer initializes embedded kobjects in
struct mem_ctl_info.  Therefore edac_mc_free() can no longer simply
decrement a kobject reference count to free the allocated memory unless
the memory controller driver module had also called edac_mc_add_mc().

Now edac_mc_free() will check if the newly embedded struct device has
been registered with sysfs before using either the standard device
release functions or freeing the data structures itself with logic
pulled out of the error path of edac_mc_alloc().

The BUG this patch resolves for me:

  BUG: unable to handle kernel NULL pointer dereference at   (null)
  EIP is at __wake_up_common+0x1a/0x6a
  Process modprobe (pid: 933, ti=f3dc6000 task=f3db9520 task.ti=f3dc6000)
  Call Trace:
    complete_all+0x3f/0x50
    device_pm_remove+0x23/0xa2
    device_del+0x34/0x142
    edac_unregister_sysfs+0x3b/0x5c [edac_core]
    edac_mc_free+0x29/0x2f [edac_core]
    e7xxx_probe1+0x268/0x311 [e7xxx_edac]
    e7xxx_init_one+0x56/0x61 [e7xxx_edac]
    local_pci_probe+0x13/0x15
  ...

Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/edac/edac_mc.c