Re: BUG: unable to handle kernel NULL pointer dereference - nfs v3

From: Satyam Sharma
Date: Fri Jul 20 2007 - 03:13:30 EST


Hi,

On 7/20/07, Neil Brown <neilb@xxxxxxx> wrote:
On Thursday July 19, satyam.sharma@xxxxxxxxx wrote:
> Ugh, not a good day for me today ... my earlier conclusion was right,
> but not the reasoning behind it ... hopefully this time I'll do better :-)


Looks good. Thanks for your helpful analysis.

Thanks, good to know I was of some help :-)

[ For pedantic correctness, of course, s/word/dword/ in the last mail,
considering "word" size is still 16-bit on i386 -- but then that's the
weird backward-compatibility nomenclature/behaviour of i386. ]

> 0x34 bytes is the offset of ex_uuid in struct fh_export.
> %ecx == 0, which means ex_uuid was NULL.

Yup. That shouldn't happen, but I can see that it is possible.

There was another case were ex_uuid could conceivably be referenced
while NULL that I fixed a little while ago. Looks like I need to fix
this one too. Something like the following.

Thanks,
NeilBrown

Signed-off-by: Neil Brown <neilb@xxxxxxx>

### Diffstat output
./fs/nfsd/nfsfh.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff .prev/fs/nfsd/nfsfh.c ./fs/nfsd/nfsfh.c
--- .prev/fs/nfsd/nfsfh.c 2007-07-13 17:41:48.000000000 +1000
+++ ./fs/nfsd/nfsfh.c 2007-07-20 12:53:36.000000000 +1000
@@ -566,13 +566,23 @@ enum fsid_source fsid_source(struct svc_
case FSID_DEV:
case FSID_ENCODE_DEV:
case FSID_MAJOR_MINOR:
- return FSIDSOURCE_DEV;
+ if (fhp->fh_export->ex_dentry->d_inode->i_sb->s_type->fs_flags
+ & FS_REQUIRES_DEV)
+ return FSIDSOURCE_DEV;
+ break;
case FSID_NUM:
- return FSIDSOURCE_FSID;
- default:
if (fhp->fh_export->ex_flags & NFSEXP_FSID)
return FSIDSOURCE_FSID;
- else
- return FSIDSOURCE_UUID;
+ break;
+ default:
+ break;
}
+ /* either a UUID type filehandle, or the filehandle doesn't
+ * match the export.
+ */
+ if (fhp->fh_export->ex_flags & NFSEXP_FSID)
+ return FSIDSOURCE_FSID;
+ if (fhp->fh_export->ex_uuid)
+ return FSIDSOURCE_UUID;
+ return FSIDSOURCE_DEV;
}


David, please try this and let us know if it solves your problems.

Thanks,
Satyam
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