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hashtable: fix environment variable corruption

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Only first previously deleted entry was recognized, leading hsearch_r
to think that there was no previously deleted entry. It then conluded
that a free entry was found, even if there were no free entries and it
overwrote a random entry.

This patch makes sure all deleted or free entries are always found and
also introduces constants for the 0 and -1 numbers. Unit tests to excersise a
simple hash table usage and catch the corruption were added.

To trash your environment, simply run this loop:

setenv i 0
while true; do
    setenv v_$i $i
    setenv v_$i
    setexpr i $i + 1
done

Signed-off-by: Roman Kapl <rka@sysgo.com>
This commit is contained in:
Roman Kapl
2019-01-30 11:39:54 +01:00
committed by Tom Rini
parent 4d9dbb1fbb
commit 9dfdbd9f0c
3 changed files with 136 additions and 3 deletions
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13
lib/hashtable.c
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@@ -40,6 +40,9 @@
#define CONFIG_ENV_MAX_ENTRIES 512
#endif
#define USED_FREE 0
#define USED_DELETED -1
#include <env_callback.h>
#include <env_flags.h>
#include <search.h>
@@ -303,7 +306,7 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
*/
unsigned hval2;
if (htab->table[idx].used == -1
if (htab->table[idx].used == USED_DELETED
&& !first_deleted)
first_deleted = idx;
@@ -335,13 +338,17 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
if (idx == hval)
break;
if (htab->table[idx].used == USED_DELETED
&& !first_deleted)
first_deleted = idx;
/* If entry is found use it. */
ret = _compare_and_overwrite_entry(item, action, retval,
htab, flag, hval, idx);
if (ret != -1)
return ret;
}
while (htab->table[idx].used);
while (htab->table[idx].used != USED_FREE);
}
/* An empty bucket has been found. */
@@ -433,7 +440,7 @@ static void _hdelete(const char *key, struct hsearch_data *htab, ENTRY *ep,
free(ep->data);
ep->callback = NULL;
ep->flags = 0;
htab->table[idx].used = -1;
htab->table[idx].used = USED_DELETED;
--htab->filled;
}