Re: [PATCH 4/4] lib/sysfs: fix format overflow

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On 29 May 2017 at 11:09, Karel Zak <kzak@xxxxxxxxxx> wrote:
> On Sat, May 27, 2017 at 07:24:09PM +0100, Sami Kerola wrote:
>> lib/sysfs.c:343:31: warning: '/start' directive output may be truncated
>> writing 6 bytes into a region of size between 1 and 256
>> [-Wformat-truncation=]
>>
>> lib/sysfs.c:372:32: warning: '/partition' directive output may be truncated
>> writing 10 bytes into a region of size between 1 and 256
>> [-Wformat-truncation=]
>>
>> Signed-off-by: Sami Kerola <kerolasa@xxxxxx>
>> ---
>>  lib/sysfs.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/sysfs.c b/lib/sysfs.c
>> index cc290faac..6272b80b4 100644
>> --- a/lib/sysfs.c
>> +++ b/lib/sysfs.c
>> @@ -307,7 +307,7 @@ static struct dirent *xreaddir(DIR *dp)
>>
>>  int sysfs_is_partition_dirent(DIR *dir, struct dirent *d, const char *parent_name)
>>  {
>> -     char path[256];
>> +     char path[strlen(d->d_name) + sizeof("/start") + 1];
>>
>>  #ifdef _DIRENT_HAVE_D_TYPE
>>       if (d->d_type != DT_DIR &&
>> @@ -356,7 +356,6 @@ dev_t sysfs_partno_to_devno(struct sysfs_cxt *cxt, int partno)
>>  {
>>       DIR *dir;
>>       struct dirent *d;
>> -     char path[256];
>>       dev_t devno = 0;
>>
>>       dir = sysfs_opendir(cxt, NULL);
>> @@ -365,6 +364,7 @@ dev_t sysfs_partno_to_devno(struct sysfs_cxt *cxt, int partno)
>>
>>       while ((d = xreaddir(dir))) {
>>               int n, maj, min;
>> +             char path[strlen(d->d_name) + sizeof("/partition") + 1];
>
> why strlen() here? Maybe we can add to c.h macro
>
>  #define ul_dname_sizeof(x)
>     (sizeof(((struct dirent *)0)->d_dname) + sizeof(x) + 1)
>
> or use PATH_MAX ...

For some reason I thought d_name would be allocated, in which case
strlen() would be
more appropriate. Thank you for pointing out it is very static 255
buffer, so added the
proposed ul_dname_sizeof() to c.h and changed the rest of the commits
accordingly.

https://github.com/kerolasa/lelux-utiliteetit/commit/5eb0ea80b376e295aca649acc8f8e2eaa91f30bb

Updates to changes are available in the git repository at:
  git://github.com/kerolasa/lelux-utiliteetit.git rc2-fixes

-- 
Sami Kerola
http://www.iki.fi/kerolasa/
--
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