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SubjectRe: BUG: unable to handle kernel NULL pointer dereference - nfs v3
Hi,

On 7/20/07, Neil Brown <neilb@suse.de> wrote:
> On Thursday July 19, satyam.sharma@gmail.com 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@suse.de>
>
> ### 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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