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

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On Wed, Dec 06, 2017 at 01:10:14PM -0700, Ross Zwisler wrote:
> 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@xxxxxxxxxxxxxxx>
> > > Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > > 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?

It sure looks that way.

--D

> - Ross
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