lkml.org 
[lkml]   [2018]   [Jun]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
SubjectRe: include/linux/string.h:246:9: warning: '__builtin_strncpy' output truncated before terminating nul copying 4 bytes from a string of the same length
On Tue, May 29, 2018 at 4:35 AM, kbuild test robot <lkp@intel.com> wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 786b71f5b754273ccef6d9462e52062b3e1f9877
> commit: 854e55ad289ef8888e7991f0ada85d5846f5afb9 objtool, perf: Fix GCC 8 -Wrestrict error
> date: 2 months ago
> config: x86_64-randconfig-s4-05290856 (attached as .config)
> compiler: gcc-8 (Debian 8.1.0-3) 8.1.0
> reproduce:
> git checkout 854e55ad289ef8888e7991f0ada85d5846f5afb9
> # save the attached .config to linux build tree
> make ARCH=x86_64
>

I guess it's easy to fix by

--- a/drivers/video/fbdev/uvesafb.c
+++ b/drivers/video/fbdev/uvesafb.c
@@ -422,7 +422,7 @@ static int uvesafb_vbe_getinfo(struct uvesafb_ktask *task,
task->t.flags = TF_VBEIB;
task->t.buf_len = sizeof(struct vbe_ib);
task->buf = &par->vbe_ib;
- strncpy(par->vbe_ib.vbe_signature, "VBE2", 4);
+ snprintf(par->vbe_ib.vbe_signature,
sizeof(par->vbe_ib.vbe_signature), "VBE2");

The question is do we want this to just shut up a compiler? It's
obviously false positive.

> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/bitmap.h:9,
> from include/linux/cpumask.h:12,
> from arch/x86/include/asm/cpumask.h:5,
> from arch/x86/include/asm/msr.h:11,
> from arch/x86/include/asm/processor.h:21,
> from arch/x86/include/asm/cpufeature.h:5,
> from arch/x86/include/asm/thread_info.h:53,
> from include/linux/thread_info.h:38,
> from arch/x86/include/asm/preempt.h:7,
> from include/linux/preempt.h:81,
> from include/linux/spinlock.h:51,
> from include/linux/seqlock.h:36,
> from include/linux/time.h:6,
> from include/linux/stat.h:19,
> from include/linux/module.h:10,
> from drivers/video/fbdev/uvesafb.c:12:
> In function 'strncpy',
> inlined from 'uvesafb_vbe_getinfo' at drivers/video/fbdev/uvesafb.c:425:2:
>>> include/linux/string.h:246:9: warning: '__builtin_strncpy' output truncated before terminating nul copying 4 bytes from a string of the same length [-Wstringop-truncation]
> return __builtin_strncpy(p, q, size);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> vim +/__builtin_strncpy +246 include/linux/string.h
>
> 6974f0c4 Daniel Micay 2017-07-12 237
> 6974f0c4 Daniel Micay 2017-07-12 238 #if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
> 6974f0c4 Daniel Micay 2017-07-12 239 __FORTIFY_INLINE char *strncpy(char *p, const char *q, __kernel_size_t size)
> 6974f0c4 Daniel Micay 2017-07-12 240 {
> 6974f0c4 Daniel Micay 2017-07-12 241 size_t p_size = __builtin_object_size(p, 0);
> 6974f0c4 Daniel Micay 2017-07-12 242 if (__builtin_constant_p(size) && p_size < size)
> 6974f0c4 Daniel Micay 2017-07-12 243 __write_overflow();
> 6974f0c4 Daniel Micay 2017-07-12 244 if (p_size < size)
> 6974f0c4 Daniel Micay 2017-07-12 245 fortify_panic(__func__);
> 6974f0c4 Daniel Micay 2017-07-12 @246 return __builtin_strncpy(p, q, size);
> 6974f0c4 Daniel Micay 2017-07-12 247 }
> 6974f0c4 Daniel Micay 2017-07-12 248
>
> :::::: The code at line 246 was first introduced by commit
> :::::: 6974f0c4555e285ab217cee58b6e874f776ff409 include/linux/string.h: add the option of fortified string.h functions
>
> :::::: TO: Daniel Micay <danielmicay@gmail.com>
> :::::: CC: Linus Torvalds <torvalds@linux-foundation.org>
>
> ---
> 0-DAY kernel test infrastructure Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all Intel Corporation


--
With Best Regards,
Andy Shevchenko

\
 
 \ /
  Last update: 2018-06-05 17:20    [W:0.044 / U:3.616 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site