Re: [xfsprogs PATCH v2 1/3] xfs_io: fix compiler warnings in getfsmap code

Ross Zwisler
2017-12-06T20:05:43Z

On Wed, Dec 06, 2017 at 11:27:43AM +1100, Dave Chinner wrote:
> On Tue, Dec 05, 2017 at 04:56:49PM -0700, Ross Zwisler wrote:
> > I recently upgraded my compiler from
> > gcc (GCC) 6.4.1 20170727 (Red Hat 6.4.1-1)
> > to
> > gcc (GCC) 7.2.1 20170915 (Red Hat 7.2.1-2)
> > and started getting a bunch of compiler warnings in io/fsmap.c:
> >
> > fsmap.c: In function ‘fsmap_f’:
> > fsmap.c:228:40: warning: ‘%lld’ directive output may be truncated writing
> > between 1 and 17 bytes into a region of size between 12 and 28
> > [-Wformat-truncation=]
> > snprintf(bbuf, sizeof(bbuf), "[%lld..%lld]:",
> > ^~~~
> > fsmap.c:228:32: note: directive argument in the range [0, 36028797018963967]
> > snprintf(bbuf, sizeof(bbuf), "[%lld..%lld]:",
> > ^~~~~~~~~~~~~~~
> > fsmap.c:228:3: note: ‘snprintf’ output between 8 and 40 bytes into a
> > destination of size 32
> > snprintf(bbuf, sizeof(bbuf), "[%lld..%lld]:",
> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > (long long)BTOBBT(p->fmr_physical),
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > (long long)BTOBBT(p->fmr_physical + p->fmr_length - 1));
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > The issue is that 'bbuf' is only defined to be 32 characters wide, but each
> > signed long long can potentially print as many as 19 characters
> > (9223372036854775807 is the max value). The format we're using for bbuf is
> > "[%lld..%lld]:" which has 2 signed long longs plus 6 other characters
> > "[..]:\0", which means it's possible we'll print up to 44 characters,
> > overflowing our 32 char buffer.
> >
> > Fix this by bumping all the buffer sizes in dump_map_verbose() to 64
> > characters.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > Cc: Darrick J. Wong <darrick.wong@oracle.com>
> > Fixes: 3fcab549a234 ("xfs_io: support the new getfsmap ioctl")
>
> FYI, I posted a fix for this weeks ago. I think Eric has already
> picked it up, but it hasn't been pushed out into the for-next branch
> yet.

I'm seeing similar new compiler warnings when compiling xfstests:

write_log.c: In function ‘wlog_open’:
write_log.c:124:37: warning: ‘%s’ directive writing up to 1023 bytes into a region of size 224 [-Wformat-overflow=]
"Could not open write_log - open(%s, %#o, %#o) failed: %s\n",
^~
write_log.c:124:4: note: directive argument in the range [1089, 2047]
"Could not open write_log - open(%s, %#o, %#o) failed: %s\n",
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

etc.

I don't see any patches posted that fix these, as of yet. As far as you know,
am I correct in thinking that these still need to be fixed?

- Ross