Re: [PATCH 1/3] mdadm: Replace snprintf with strncpy at some places to avoid truncation

[Xiao Ni <xni@redhat.com>]

----- Original Message -----
> From: "jes sorensen" <jes.sorensen@gmail.com>
> To: "Xiao Ni" <xni@redhat.com>
> Cc: linux-raid@vger.kernel.org, ncroxon@redhat.com, "artur paszkiewicz" <artur.paszkiewicz@intel.com>
> Sent: Saturday, March 18, 2017 3:55:43 AM
> Subject: Re: [PATCH 1/3] mdadm: Replace snprintf with strncpy at some places to avoid truncation
> 
> Xiao Ni <xni@redhat.com> writes:
> > In gcc7 there are some building errors like:
> > directive output may be truncated writing up to 31 bytes into a region of
> > size 24
> > snprintf(str, MPB_SIG_LEN, %s, mpb->sig);
> >
> > It just need to copy one string to target. So use strncpy to replace it.
> >
> > Signed-off-by: Xiao Ni <xni@redhat.com>
> > ---
> >  super-intel.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/super-intel.c b/super-intel.c
> > index d5e9517..e1618f1 100644
> > --- a/super-intel.c
> > +++ b/super-intel.c
> > @@ -1811,7 +1811,8 @@ static void examine_super_imsm(struct supertype *st,
> > char *homehost)
> >  	__u32 reserved = imsm_reserved_sectors(super, super->disks);
> >  	struct dl *dl;
> >  
> > -	snprintf(str, MPB_SIG_LEN, "%s", mpb->sig);
> > +	strncpy(str, (char *)mpb->sig, MPB_SIG_LEN);
> > +	str[MPB_SIG_LEN-1] = '\0';
> >  	printf("          Magic : %s\n", str);
> >  	snprintf(str, strlen(MPB_VERSION_RAID0), "%s", get_imsm_version(mpb));
> >  	printf("        Version : %s\n", get_imsm_version(mpb));
> 
> Given str is defined as 'char str[MAX_SIGNATURE_LENGTH]', it would be
> more correct to use MAX_SIGNATURE_LENGTH as the size limit here.

I talked with Artur about this. It should use MPB_SIG_LEN, because the mpb->sig
has version after the signature. It will print more if use MAX_SIGNATURE_LENGTH.

> 
> > @@ -5227,7 +5228,7 @@ static int init_super_imsm_volume(struct supertype
> > *st, mdu_array_info_t *info,
> >  			disk->status = CONFIGURED_DISK | FAILED_DISK;
> >  			disk->scsi_id = __cpu_to_le32(~(__u32)0);
> >  			snprintf((char *) disk->serial, MAX_RAID_SERIAL_LEN,
> > -				 "missing:%d", i);
> > +				 "missing:%d", (__u8)i);
> >  		}
> >  		find_missing(super);
> >  	} else {
> 
> This is unrelated to the commit message.

I'll re-send this patch later.

Regards
Xiao
> 
> > @@ -7142,14 +7143,16 @@ static int update_subarray_imsm(struct supertype
> > *st, char *subarray,
> >  
> >  			u->type = update_rename_array;
> >  			u->dev_idx = vol;
> > -			snprintf((char *) u->name, MAX_RAID_SERIAL_LEN, "%s", name);
> > +			strncpy((char *) u->name, name, MAX_RAID_SERIAL_LEN);
> > +			u->name[MAX_RAID_SERIAL_LEN-1] = '\0';
> >  			append_metadata_update(st, u, sizeof(*u));
> >  		} else {
> >  			struct imsm_dev *dev;
> >  			int i;
> >  
> >  			dev = get_imsm_dev(super, vol);
> > -			snprintf((char *) dev->volume, MAX_RAID_SERIAL_LEN, "%s", name);
> > +			strncpy((char *) dev->volume, name, MAX_RAID_SERIAL_LEN);
> > +			dev->volume[MAX_RAID_SERIAL_LEN-1] = '\0';
> >  			for (i = 0; i < mpb->num_raid_devs; i++) {
> >  				dev = get_imsm_dev(super, i);
> >  				handle_missing(super, dev);
> 
> These two look fine.
> 
> Jes
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