Re: [Xen-devel] [PATCH v3] tools: fix several "format-truncation" warnings with GCC 7

[Julien Grall <julien.grall@xxxxxxx>]

On 06/20/2017 12:02 PM, Wei Liu wrote:
> On Tue, Jun 20, 2017 at 11:58:53AM +0100, Julien Grall wrote:
> > Hi Wei,
> >
> > On 06/19/2017 12:39 PM, Wei Liu wrote:
> > > On Wed, Jun 14, 2017 at 09:11:48AM +0800, Zhongze Liu wrote:
> > > > GCC 7.1.1 complains that several buffers passed to snprintf() in xenpmd
> > > > and tools/ocmal/xc are too small to hold the largest possible resulting string,
> > > > which is calculated by adding up the maximum length of all the substrings.
> > > >
> > > > The warnings are treated as errors by -Werror, and goes like this (abbreviated):
> > > >
> > > > xenpmd.c:94:36: error: ‘%s’ directive output may be truncated writing up to
> > > > 255 bytes into a region of size 13 [-Werror=format-truncation=]
> > > >        #define BATTERY_INFO_FILE_PATH "/proc/acpi/battery/%s/info"
> > > >                                       ^
> > > > xenpmd.c:113:13: note: ‘snprintf’ output between 25 and 280 bytes into a
> > > > destination of size 32
> > > >
> > > > xenpmd.c:95:37: error: ‘%s’ directive output may be truncated writing up to
> > > > 255 bytes into a region of size 13 [-Werror=format-truncation=]
> > > >        #define BATTERY_STATE_FILE_PATH "/proc/acpi/battery/%s/state"
> > > >                                        ^
> > > > xenpmd.c:116:13: note: ‘snprintf’ output between 26 and 281 bytes into a
> > > > destination of size 32
> > > >
> > > > xenctrl_stubs.c:65:15: error: ‘%s’ directive output may be truncated writing
> > > > up to 1023 bytes into a region of size 252 [-Werror=format-truncation=]
> > > >         "%d: %s: %s", error->code,
> > > >                  ^~
> > > > xenctrl_stubs.c:64:4: note: ‘snprintf’ output 5 or more bytes (assuming 1028)
> > > > into a destination of size 256
> > > >
> > > > Enlarge the size of these buffers as suggested by the complier
> > > > (and slightly rounded) to fix the warnings.
> > > >
> > > > No functional changes.
> > > >
> > > > Signed-off-by: Zhongze Liu <blackskygg@xxxxxxxxx>
> > > > Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > > Applied.
> > >
> > > Julien, consider this for 4.9?
> > Looking quickly at the patch, it sounds a bit strange to allocate 1028 bytes
> > on the stack. It is more than 1/8 of default stack in Linux (8K). Are we
> > sure the stack will never explode?
> The default stack size is 8M, not 8K so we it be fine.
Sorry I misread the unit.

Release-acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

--
Julien Grall

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