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Re: bin/73337: nsswitch: potential invalid free



The following reply was made to PR bin/73337; it has been noted by GNATS.

From: Bruce Cran <bruce_(_at_)_cran_(_dot_)_org_(_dot_)_uk>
To: bug-followup_(_at_)_FreeBSD_(_dot_)_org, nectar_(_at_)_FreeBSD_(_dot_)_org
Cc:  
Subject: Re: bin/73337: nsswitch: potential invalid free
Date: Sat, 12 Jan 2008 11:01:48 +0000

 This still appears to be a problem on 7.0-PRERELEASE: single-threaded 
 applications get returned a statically-allocated [name]_state structure, 
 but all of the [name]_endstate functions such as dns_endstate assume 
 that the memory has been dynamically allocated - and so attempt to 
 free() a pointer which wasn't obtained through malloc().  I think the 
 patch below would fix the problem.
 
 --- nss_tls.h.old       2008-01-12 00:21:20.000000000 +0000
 +++ nss_tls.h   2008-01-12 10:54:17.000000000 +0000
 @@ -50,12 +50,18 @@
  static int                                                     \
  name##_getstate(struct name##_state **p)                       \
  {                                                              \
 -       static struct name##_state st;                          \
 +       static struct name##_state *st = NULL;                          \
         static pthread_once_t   keyinit = PTHREAD_ONCE_INIT;    \
         int                     rv;                             \
                                                                 \
         if (!__isthreaded || _pthread_main_np() != 0) {         \
 -               *p = &st;                                       \
 +               if (st == NULL) {               \
 +                       st = calloc(1, sizeof(*st));            \
 +                       if (st == NULL)         \
 +                               return (ENOMEM);    \
 +               }                           \
 +                                          \
 +               *p = st;                                        \
                 return (0);                                     \
         }                                                       \
         rv = _pthread_once(&keyinit, name##_keyinit);           \
 
 
 --
 Bruce Cran
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