On Mon, Apr 22, 2019 at 03:48:03PM -0500, Eric Sandeen wrote:
> On 4/22/19 10:45 AM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Fix a number of complaints about feeding sizeof(dest) directly to
> > strncpy. We do this by declaring the char arrays to be one larger
> > than necessary and subtracting one, to ensure that we never overfill
> > the buffer.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Hm, you don't actually do what the changelog says, do you? No buffer
> changes size in this patch.
I'll change it to:
"Fix a number of complaints about feeding sizeof(dest) directly to
strncpy. We do this by feeding strncpy the length of the buffer minus
one, having checked that the allocated space are long enough."
> And FWIW, neither of these was actually a real problem (fgets guarantees
> a null in the string) but hey, whatever makes gcc happy I guess?
>
> (I think we lose a char in the quota array, but 511 chars ought to be
> enough for anybody right?)
Well... the quota one is reading lines straight out of a file, right?
So that probably ought to be char buf[PATH_MAX + length of other junk in
the line], though with the current lower limit now nobody's complained
so maybe it's fine....
--D
> Patch seems fine, though.
>
> > ---
> > mkfs/xfs_mkfs.c | 13 +++++++++++--
> > quota/edit.c | 9 ++++++---
> > 2 files changed, 17 insertions(+), 5 deletions(-)
> >
> >
> > diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> > index 3e2ef92d..db3ad38e 100644
> > --- a/mkfs/xfs_mkfs.c
> > +++ b/mkfs/xfs_mkfs.c
> > @@ -3270,8 +3270,17 @@ finish_superblock_setup(
> > struct xfs_mount *mp,
> > struct xfs_sb *sbp)
> > {
> > - if (cfg->label)
> > - strncpy(sbp->sb_fname, cfg->label, sizeof(sbp->sb_fname));
> > + if (cfg->label) {
> > + size_t label_len;
> > +
> > + /*
> > + * Labels are null terminated unless the string fits exactly
> > + * in the label field, so assume sb_fname is zeroed and then
> > + * do a memcpy because the destination isn't a normal C string.
> > + */
> > + label_len = min(sizeof(sbp->sb_fname), strlen(cfg->label));
> > + memcpy(sbp->sb_fname, cfg->label, label_len);
> > + }
> >
> > sbp->sb_dblocks = cfg->dblocks;
> > sbp->sb_rblocks = cfg->rtblocks;
> > diff --git a/quota/edit.c b/quota/edit.c
> > index b10a5b34..f9938b8a 100644
> > --- a/quota/edit.c
> > +++ b/quota/edit.c
> > @@ -368,8 +368,7 @@ restore_file(
> > uint type)
> > {
> > char buffer[512];
> > - char devbuffer[512];
> > - char *dev = NULL;
> > + char dev[512];
> > uint mask;
> > int cnt;
> > uint32_t id;
> > @@ -377,7 +376,11 @@ restore_file(
> >
> > while (fgets(buffer, sizeof(buffer), fp) != NULL) {
> > if (strncmp("fs = ", buffer, 5) == 0) {
> > - dev = strncpy(devbuffer, buffer+5, sizeof(devbuffer));
> > + /*
> > + * Copy the device name to dev, strip off the trailing
> > + * newline, and move on to the next line.
> > + */
> > + strncpy(dev, buffer + 5, sizeof(dev) - 1);
> > dev[strlen(dev) - 1] = '\0';
> > continue;
> > }
> >
