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nscd: Use struct scratch_buffer, not extend_alloca in most caches [BZ #18023]

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This replaces the ERANGE retry loops with loops which have heap
fallback.  Heap allocation might actually be required for extremely
large NSS results.
This commit is contained in:
Florian Weimer 2018-06-25 16:04:29 +02:00
parent 318bad78b0
commit 2f9f0d182e
5 changed files with 84 additions and 152 deletions
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9
ChangeLog
View File

@ -1,3 +1,12 @@
2018-06-25 Florian Weimer <fweimer@redhat.com>
[BZ #18023]
* nscd/grpcache.c (addgrbyX): Use struct scratch_buffer instead
of extend_alloca.
* nscd/hstcache.c (addhstbyX): Likewise.
* nscd/pwdcache.c (addpwbyX): Likewise.
* nscd/servicescache.c (addservbyX): Likewise.
2018-06-25 Florian Weimer <fweimer@redhat.com>
[BZ #18023]

57
nscd/grpcache.c
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@ -16,7 +16,6 @@
You should have received a copy of the GNU General Public License
along with this program; if not, see <http://www.gnu.org/licenses/>. */
#include <alloca.h>
#include <assert.h>
#include <errno.h>
#include <error.h>
@ -32,6 +31,7 @@
#include <sys/mman.h>
#include <sys/socket.h>
#include <stackinfo.h>
#include <scratch_buffer.h>
#include "nscd.h"
#include "dbg_log.h"
@ -417,12 +417,12 @@ addgrbyX (struct database_dyn *db, int fd, request_header *req,
look again in the table whether the dataset is now available. We
simply insert it. It does not matter if it is in there twice. The
pruning function only will look at the timestamp. */
size_t buflen = 1024;
char *buffer = (char *) alloca (buflen);
struct group resultbuf;
struct group *grp;
bool use_malloc = false;
int errval = 0;
struct scratch_buffer tmpbuf;
scratch_buffer_init (&tmpbuf);
if (__glibc_unlikely (debug_level > 0))
{
@ -432,43 +432,24 @@ addgrbyX (struct database_dyn *db, int fd, request_header *req,
dbg_log (_("Reloading \"%s\" in group cache!"), keystr);
}
while (lookup (req->type, key, &resultbuf, buffer, buflen, &grp) != 0
while (lookup (req->type, key, &resultbuf,
tmpbuf.data, tmpbuf.length, &grp) != 0
&& (errval = errno) == ERANGE)
{
errno = 0;
if (__glibc_unlikely (buflen > 32768))
{
char *old_buffer = buffer;
buflen *= 2;
buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
if (buffer == NULL)
{
/* We ran out of memory. We cannot do anything but
sending a negative response. In reality this should
never happen. */
grp = NULL;
buffer = old_buffer;
/* We set the error to indicate this is (possibly) a
temporary error and that it does not mean the entry
is not available at all. */
errval = EAGAIN;
break;
}
use_malloc = true;
}
else
/* Allocate a new buffer on the stack. If possible combine it
with the previously allocated buffer. */
buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen);
}
if (!scratch_buffer_grow (&tmpbuf))
{
/* We ran out of memory. We cannot do anything but sending a
negative response. In reality this should never
happen. */
grp = NULL;
/* We set the error to indicate this is (possibly) a temporary
error and that it does not mean the entry is not available
at all. */
errval = EAGAIN;
break;
}
time_t timeout = cache_addgr (db, fd, req, keystr, grp, uid, he, dh, errval);
if (use_malloc)
free (buffer);
scratch_buffer_free (&tmpbuf);
return timeout;
}

58
nscd/hstcache.c
View File

@ -34,6 +34,7 @@
#include <arpa/nameser.h>
#include <sys/mman.h>
#include <stackinfo.h>
#include <scratch_buffer.h>
#include "nscd.h"
#include "dbg_log.h"
@ -432,11 +433,8 @@ addhstbyX (struct database_dyn *db, int fd, request_header *req,
look again in the table whether the dataset is now available. We
simply insert it. It does not matter if it is in there twice. The
pruning function only will look at the timestamp. */
int buflen = 1024;
char *buffer = (char *) alloca (buflen);
struct hostent resultbuf;
struct hostent *hst;
bool use_malloc = false;
int errval = 0;
int32_t ttl = INT32_MAX;
@ -456,46 +454,30 @@ addhstbyX (struct database_dyn *db, int fd, request_header *req,
dbg_log (_("Reloading \"%s\" in hosts cache!"), (char *) str);
}
while (lookup (req->type, key, &resultbuf, buffer, buflen, &hst, &ttl) != 0
struct scratch_buffer tmpbuf;
scratch_buffer_init (&tmpbuf);
while (lookup (req->type, key, &resultbuf,
tmpbuf.data, tmpbuf.length, &hst, &ttl) != 0
&& h_errno == NETDB_INTERNAL
&& (errval = errno) == ERANGE)
{
errno = 0;
if (__glibc_unlikely (buflen > 32768))
{
char *old_buffer = buffer;
buflen *= 2;
buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
if (buffer == NULL)
{
/* We ran out of memory. We cannot do anything but
sending a negative response. In reality this should
never happen. */
hst = NULL;
buffer = old_buffer;
/* We set the error to indicate this is (possibly) a
temporary error and that it does not mean the entry
is not available at all. */
h_errno = TRY_AGAIN;
errval = EAGAIN;
break;
}
use_malloc = true;
}
else
/* Allocate a new buffer on the stack. If possible combine it
with the previously allocated buffer. */
buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen);
}
if (!scratch_buffer_grow (&tmpbuf))
{
/* We ran out of memory. We cannot do anything but sending a
negative response. In reality this should never
happen. */
hst = NULL;
/* We set the error to indicate this is (possibly) a temporary
error and that it does not mean the entry is not
available at all. */
h_errno = TRY_AGAIN;
errval = EAGAIN;
break;
}
time_t timeout = cache_addhst (db, fd, req, key, hst, uid, he, dh,
h_errno == TRY_AGAIN ? errval : 0, ttl);
if (use_malloc)
free (buffer);
scratch_buffer_free (&tmpbuf);
return timeout;
}

56
nscd/pwdcache.c
View File

@ -16,7 +16,6 @@
You should have received a copy of the GNU General Public License
along with this program; if not, see <http://www.gnu.org/licenses/>. */
#include <alloca.h>
#include <assert.h>
#include <errno.h>
#include <error.h>
@ -32,6 +31,7 @@
#include <sys/mman.h>
#include <sys/socket.h>
#include <stackinfo.h>
#include <scratch_buffer.h>
#include "nscd.h"
#include "dbg_log.h"
@ -395,12 +395,11 @@ addpwbyX (struct database_dyn *db, int fd, request_header *req,
look again in the table whether the dataset is now available. We
simply insert it. It does not matter if it is in there twice. The
pruning function only will look at the timestamp. */
size_t buflen = 1024;
char *buffer = (char *) alloca (buflen);
struct passwd resultbuf;
struct passwd *pwd;
bool use_malloc = false;
int errval = 0;
struct scratch_buffer tmpbuf;
scratch_buffer_init (&tmpbuf);
if (__glibc_unlikely (debug_level > 0))
{
@ -410,45 +409,26 @@ addpwbyX (struct database_dyn *db, int fd, request_header *req,
dbg_log (_("Reloading \"%s\" in password cache!"), keystr);
}
while (lookup (req->type, key, &resultbuf, buffer, buflen, &pwd) != 0
while (lookup (req->type, key, &resultbuf,
tmpbuf.data, tmpbuf.length, &pwd) != 0
&& (errval = errno) == ERANGE)
{
errno = 0;
if (__glibc_unlikely (buflen > 32768))
{
char *old_buffer = buffer;
buflen *= 2;
buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
if (buffer == NULL)
{
/* We ran out of memory. We cannot do anything but
sending a negative response. In reality this should
never happen. */
pwd = NULL;
buffer = old_buffer;
/* We set the error to indicate this is (possibly) a
temporary error and that it does not mean the entry
is not available at all. */
errval = EAGAIN;
break;
}
use_malloc = true;
}
else
/* Allocate a new buffer on the stack. If possible combine it
with the previously allocated buffer. */
buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen);
}
if (!scratch_buffer_grow (&tmpbuf))
{
/* We ran out of memory. We cannot do anything but sending a
negative response. In reality this should never
happen. */
pwd = NULL;
/* We set the error to indicate this is (possibly) a temporary
error and that it does not mean the entry is not available
at all. */
errval = EAGAIN;
break;
}
/* Add the entry to the cache. */
time_t timeout = cache_addpw (db, fd, req, keystr, pwd, c_uid, he, dh,
errval);
if (use_malloc)
free (buffer);
scratch_buffer_free (&tmpbuf);
return timeout;
}

56
nscd/servicescache.c
View File

@ -16,7 +16,6 @@
You should have received a copy of the GNU General Public License
along with this program; if not, see <http://www.gnu.org/licenses/>. */
#include <alloca.h>
#include <assert.h>
#include <errno.h>
#include <libintl.h>
@ -25,6 +24,7 @@
#include <stdint.h>
#include <sys/mman.h>
#include <kernel-features.h>
#include <scratch_buffer.h>
#include "nscd.h"
#include "dbg_log.h"
@ -346,12 +346,11 @@ addservbyX (struct database_dyn *db, int fd, request_header *req,
look again in the table whether the dataset is now available. We
simply insert it. It does not matter if it is in there twice. The
pruning function only will look at the timestamp. */
size_t buflen = 1024;
char *buffer = (char *) alloca (buflen);
struct servent resultbuf;
struct servent *serv;
bool use_malloc = false;
int errval = 0;
struct scratch_buffer tmpbuf;
scratch_buffer_init (&tmpbuf);
if (__glibc_unlikely (debug_level > 0))
{
@ -361,43 +360,24 @@ addservbyX (struct database_dyn *db, int fd, request_header *req,
dbg_log (_("Reloading \"%s\" in services cache!"), key);
}
while (lookup (req->type, key, &resultbuf, buffer, buflen, &serv) != 0
while (lookup (req->type, key, &resultbuf,
tmpbuf.data, tmpbuf.length, &serv) != 0
&& (errval = errno) == ERANGE)
{
errno = 0;
if (__glibc_unlikely (buflen > 32768))
{
char *old_buffer = buffer;
buflen *= 2;
buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
if (buffer == NULL)
{
/* We ran out of memory. We cannot do anything but
sending a negative response. In reality this should
never happen. */
serv = NULL;
buffer = old_buffer;
/* We set the error to indicate this is (possibly) a
temporary error and that it does not mean the entry
is not available at all. */
errval = EAGAIN;
break;
}
use_malloc = true;
}
else
/* Allocate a new buffer on the stack. If possible combine it
with the previously allocated buffer. */
buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen);
}
if (!scratch_buffer_grow (&tmpbuf))
{
/* We ran out of memory. We cannot do anything but sending a
negative response. In reality this should never
happen. */
serv = NULL;
/* We set the error to indicate this is (possibly) a temporary
error and that it does not mean the entry is not available
at all. */
errval = EAGAIN;
break;
}
time_t timeout = cache_addserv (db, fd, req, key, serv, uid, he, dh, errval);
if (use_malloc)
free (buffer);
scratch_buffer_free (&tmpbuf);
return timeout;
}