lkml.org 
[lkml]   [2012]   [Sep]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] edac_mc: fix messy kfree calls in the error path
coccinelle warns about:

+ drivers/edac/edac_mc.c:429:9-23: ERROR: reference preceded by free on line 429

421 if (mci->csrows) {
> 422 for (chn = 0; chn < tot_channels; chn++) {
423 csr = mci->csrows[chn];
424 if (csr) {
> 425 for (chn = 0; chn < tot_channels; chn++)
426 kfree(csr->channels[chn]);
427 kfree(csr);
428 }
> 429 kfree(mci->csrows[i]);
430 }
431 kfree(mci->csrows);
432 }
and that code block seem to mess things up in several ways (double free, memory
leak, out-of-bound reads etc.):

L422: The iterator "chn" and bound "tot_channels" are totally wrong. Should be
"row" and "tot_csrows" respectively. Which means either memory leak, or
out-of-bound reads (which if does not trigger an immediate page fault
error, will further lead to kfree() on random addresses).

L425: The inner loop is reusing the same iterator "chn" as the outer loop,
which could lead to premature end of the outer loop, and hence memory leak.

L429: The array index 'i' in mci->csrows[i] is a temporary value used in
previous loops, and won't change at all in the current loop. Which
means either out-of-bound read and possibly kfree(random number), or the
same mci->csrows[i] get freed once and again, and possibly double free
for the kfree(csr) in L427.

L426/L427: a kfree(csr->channels) is needed in between to avoid leaking the memory.

The buggy code was introduced by commit de3910eb ("edac: change the mem
allocation scheme to make Documentation/kobject.txt happy") in the 3.6-rc1
merge window. Fix it by freeing up resources in this order:

free csrows[i]->channels[j]
free csrows[i]->channels
free csrows[i]
free csrows

CC: Mauro Carvalho Chehab <mchehab@redhat.com>
CC: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
drivers/edac/edac_mc.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- linux.orig/drivers/edac/edac_mc.c 2012-08-12 10:10:38.115520521 +0800
+++ linux/drivers/edac/edac_mc.c 2012-09-23 07:30:40.382206820 +0800
@@ -419,14 +419,16 @@ error:
kfree(mci->dimms);
}
if (mci->csrows) {
- for (chn = 0; chn < tot_channels; chn++) {
- csr = mci->csrows[chn];
+ for (row = 0; row < tot_csrows; row++) {
+ csr = mci->csrows[row];
if (csr) {
- for (chn = 0; chn < tot_channels; chn++)
- kfree(csr->channels[chn]);
+ if (csr->channels) {
+ for (chn = 0; chn < tot_channels; chn++)
+ kfree(csr->channels[chn]);
+ kfree(csr->channels);
+ }
kfree(csr);
}
- kfree(mci->csrows[i]);
}
kfree(mci->csrows);
}

\
 
 \ /
  Last update: 2012-09-23 02:41    [from the cache]
©2003-2011 Jasper Spaans