On Thu, Jun 18, 2015 at 03:00:04PM +0800, Kinglong Mee wrote:
> With nfsd_debug on, fh_verify prints a fixed length of filehandle as,
> nfsd: fh_verify(8: 00010001 00000000 00000000 00000000 00000000 00000000)
> nfsd: fh_verify(28: 00070001 001c0002 00000000 041f9334 9b432a4c 835d4c95)
>
> This patch lets nfsd prints a suitable length of filehandle as,
> nfsd: fh_verify(8: 00010001 00000000)
> nfsd: fh_verify(28: 00070001 001c0002 00000000 041f9334 9b432a4c 835d4c95 8cbea40f)
>
> Also, use snprintf insteads sprintf.
>
> Signed-off-by: Kinglong Mee <kinglongmee@xxxxxxxxx>
> ---
> fs/nfsd/nfsfh.c | 18 ++++++++----------
> 1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
> index 350041a..dd6a5c1 100644
> --- a/fs/nfsd/nfsfh.c
> +++ b/fs/nfsd/nfsfh.c
> @@ -650,16 +650,14 @@ fh_put(struct svc_fh *fhp)
> char * SVCFH_fmt(struct svc_fh *fhp)
> {
> struct knfsd_fh *fh = &fhp->fh_handle;
> -
> - static char buf[80];
> - sprintf(buf, "%d: %08x %08x %08x %08x %08x %08x",
> - fh->fh_size,
> - fh->fh_base.fh_pad[0],
> - fh->fh_base.fh_pad[1],
> - fh->fh_base.fh_pad[2],
> - fh->fh_base.fh_pad[3],
> - fh->fh_base.fh_pad[4],
> - fh->fh_base.fh_pad[5]);
> + /* 9 * NFS4_FHSIZE / 4 = 288 for fh_pad, 4 for fh_size, 1 for '\0' */
> + static char buf[293];
So that buffer can be shared by multiple users without any locking.
That's from the preexisting code, not your fault. Also, I don't know
whether to care about an unlikely race in debugging code.
The only risk aside from corruption of the output might be if the race
could leave the string temporarily non-null-terminated. I think that's
possible? In which case that could be prevented by making sure buf is
initialized to zeroes and is at least one byte longer than the following
code will ever write.
--b.
> + int pos = 0, i = 0;
> +
> + pos = snprintf(buf, sizeof(buf), "%d:", fh->fh_size);
> + for (i = 0; i < fh->fh_size / sizeof(__u32); i++)
> + pos += snprintf(buf + pos, sizeof(buf) - pos,
> + " %08x", fh->fh_base.fh_pad[i]);
> return buf;
> }
>
> --
> 2.4.3
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
