Messages in this thread | | | Date | Tue, 28 Mar 2017 16:29:42 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] kasan: avoid -Wmaybe-uninitialized warning |
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On Thu, 23 Mar 2017 16:04:09 +0100 Arnd Bergmann <arnd@arndb.de> wrote:
> gcc-7 produces this warning: > > mm/kasan/report.c: In function 'kasan_report': > mm/kasan/report.c:351:3: error: 'info.first_bad_addr' may be used uninitialized in this function [-Werror=maybe-uninitialized] > print_shadow_for_address(info->first_bad_addr); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > mm/kasan/report.c:360:27: note: 'info.first_bad_addr' was declared here > > The code seems fine as we only print info.first_bad_addr when there is a shadow, > and we always initialize it in that case, but this is relatively hard > for gcc to figure out after the latest rework. Adding an intialization > in the other code path gets rid of the warning. > > ... > > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -109,6 +109,8 @@ const char *get_wild_bug_type(struct kasan_access_info *info) > { > const char *bug_type = "unknown-crash"; > > + info->first_bad_addr = (void *)(-1ul); > + > if ((unsigned long)info->access_addr < PAGE_SIZE) > bug_type = "null-ptr-deref"; > else if ((unsigned long)info->access_addr < TASK_SIZE)
A weird, ugly and seemingly-unneeded statement should have a comment explaining its existence, no?
Fortunately it is no longer needed. We now have:
static void print_error_description(struct kasan_access_info *info) { const char *bug_type = "unknown-crash"; u8 *shadow_addr;
info->first_bad_addr = find_first_bad_addr(info->access_addr, info->access_size);
shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
...
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