Re: panic at umount in fscache code

[Suresh Jayaraman <sjayaraman-l3A5Bk7waGM@public.gmane.org>]

On 07/23/2010 07:22 PM, Jeff Layton wrote:
> I built a kernel based on Steve's tree, enabled the fscache option and
> got the following panic at umount. I didn't mount with -o fsc or
> anything. I have some other patches on top of Steve's tree, but I'm
> fairly certain they wouldn't affect this.
> 
> For the record, here's the fstab entry (with anonymized names):
> 
> //server.example.com/scratch	/mnt/anonymous		cifs	sec=none,user,noperm,noauto 0 0
> 
> Disabling the fscache stuff at build time makes the problem go away.
> 
> ------------------------------[snip]------------------------------
> 
> general protection fault: 0000 [#1] SMP 
> last sysfs file: /sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_map

Could you please check whether the below patch fixes the problem?

Thanks,


From: Suresh Jayaraman <sjayaraman-l3A5Bk7waGM@public.gmane.org>
Subject: [PATCH] cifs: relinquish fscache cookie before freeing CIFSTconInfo

Doh, fix a use after free bug. 

Signed-off-by: Suresh Jayaraman <sjayaraman-l3A5Bk7waGM@public.gmane.org>
---
 fs/cifs/connect.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 399b601..5480025 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1842,8 +1842,8 @@ cifs_put_tcon(struct cifsTconInfo *tcon)
 	CIFSSMBTDis(xid, tcon);
 	_FreeXid(xid);
 
-	tconInfoFree(tcon);
 	cifs_fscache_release_super_cookie(tcon);
+	tconInfoFree(tcon);
 	cifs_put_smb_ses(ses);
 }