[PATCH] elf: Do not signal LA_ACT_CONSISTENT for an empty namespace [BZ #26076]

[Carlos O'Donell]

On 7/6/20 4:40 PM, H.J. Lu via Libc-alpha wrote:
> On Mon, Jul 6, 2020 at 12:45 PM Florian Weimer via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
>>
>> The auditing interface identifies namespaces by their first loaded
>> module.  Once the namespace is empty, it is no longer possible to signal
>> LA_ACT_CONSISTENT for it because the first loaded module is already gone
>> at that point.
>>
>> Tested on i686-linux-gnu and x86_64-linux-gnu.
>>
>> ---
>>  elf/dl-close.c | 10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/elf/dl-close.c b/elf/dl-close.c
>> index 73b2817bbf..8e146ecee1 100644
>> --- a/elf/dl-close.c
>> +++ b/elf/dl-close.c
>> @@ -781,8 +781,14 @@ _dl_close_worker (struct link_map *map, bool force)
>>    if (__glibc_unlikely (do_audit))
>>      {
>>        struct link_map *head = ns->_ns_loaded;
>> -      /* Do not call the functions for any auditing object.  */
>> -      if (head->l_auditing == 0)
> 
> I assume that "head" can be NULL.  Do you have a testcase?

Yes, it's tst-auditmany in trunk right now. It fails because of this issue.

> 
>> +      /* If head is NULL, the namespace has become empty, and the
>> +        audit interface does not give us a way to signal
>> +        LA_ACT_CONSISTENT for it because the first loaded module is
>> +        used to identify the namespace.
>> +
>> +        Furthermore, do not notify auditors of the cleanup of a
>> +        failed audit module loading attempt.  */
>> +      if (head != NULL && head->l_auditing == 0)
>>         {
>>           struct audit_ifaces *afct = GLRO(dl_audit);
>>           for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
>>
> 
> 


-- 
Cheers,
Carlos.