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Fix forced loop termination in nscd database lookup.

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There are two issues with the forced loop exit in the nscd lookup:
1. the estimate of the entry size isn't pessimistic enough for all
   databases, resulting potentially is too early exits
2. the combination of 64-bit process and 32-bit nscd would lead to
   rejecting valid records in the database.
This commit is contained in:
Jakub Jelinek 2009-05-18 10:19:50 -07:00 committed by Ulrich Drepper
parent e20c4ef0ef
commit 5078fff6c4
2 changed files with 21 additions and 3 deletions
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8
ChangeLog
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@ -1,3 +1,11 @@
2009-05-18 Jakub Jelinek <jakub@redhat.com>
Ulrich Drepper <drepper@redhat.com>
* nscd/nscd_helper.c (MINIMUM_HASHENTRY_SIZE): Define.
(__nscd_cache_search): Assume each entry in the
hash chain needs one hashentry and half of datahead. Use
MINIMUM_HASHENTRY_SIZE instead of sizeof(hashentry).
2009-05-16 Ulrich Drepper <drepper@redhat.com>
* posix/sys/wait.h: Fix typos. Pretty printing.

16
nscd/nscd_helper.c
View File

@ -468,6 +468,15 @@ __nscd_get_map_ref (request_type type, const char *name,
}
/* Using sizeof (hashentry) is not always correct to determine the size of
the data structure as found in the nscd cache. The program could be
a 64-bit process and nscd could be a 32-bit process. In this case
sizeof (hashentry) would overestimate the size. The following is
the minimum size of such an entry, good enough for our tests here. */
#define MINIMUM_HASHENTRY_SIZE \
(offsetof (struct hashentry, dellist) + sizeof (int32_t))
/* Don't return const struct datahead *, as eventhough the record
is normally constant, it can change arbitrarily during nscd
garbage collection. */
@ -481,10 +490,11 @@ __nscd_cache_search (request_type type, const char *key, size_t keylen,
ref_t trail = mapped->head->array[hash];
trail = atomic_forced_read (trail);
ref_t work = trail;
size_t loop_cnt = datasize / (offsetof (struct datahead, data) + datalen);
size_t loop_cnt = datasize / (MINIMUM_HASHENTRY_SIZE
+ offsetof (struct datahead, data) / 2);
int tick = 0;
while (work != ENDREF && work + sizeof (struct hashentry) <= datasize)
while (work != ENDREF && work + MINIMUM_HASHENTRY_SIZE <= datasize)
{
struct hashentry *here = (struct hashentry *) (mapped->data + work);
ref_t here_key, here_packet;
@ -541,7 +551,7 @@ __nscd_cache_search (request_type type, const char *key, size_t keylen,
return NULL;
#endif
if (trail + sizeof (struct hashentry) > datasize)
if (trail + MINIMUM_HASHENTRY_SIZE > datasize)
return NULL;
trail = atomic_forced_read (trailelem->next);