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btree: fix tree corruption in btree_get_prev()
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The memory the parameter __key points to is used as an iterator in
btree_get_prev(), so if we save off a bkey() pointer in retry_key and
then assign that to __key, we'll end up corrupting the btree internals
when we do eg

	longcpy(__key, bkey(geo, node, i), geo->keylen);

to return the key value.  What we should do instead is use longcpy() to
copy the key value that retry_key points to __key.

This can cause a btree to get corrupted by seemingly read-only
operations such as btree_for_each_safe.

[[email protected]: avoid the double longcpy()]
Signed-off-by: Roland Dreier <[email protected]>
Acked-by: Joern Engel <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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rolandd authored and torvalds committed Jun 7, 2012
1 parent 7d8a456 commit cbf8ae3
Showing 1 changed file with 2 additions and 2 deletions.
4 changes: 2 additions & 2 deletions lib/btree.c
Original file line number Diff line number Diff line change
@@ -319,8 +319,8 @@ void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,

if (head->height == 0)
return NULL;
retry:
longcpy(key, __key, geo->keylen);
retry:
dec_key(geo, key);

node = head->node;
@@ -351,7 +351,7 @@ void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
}
miss:
if (retry_key) {
__key = retry_key;
longcpy(key, retry_key, geo->keylen);
retry_key = NULL;
goto retry;
}

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