[PATCH 5.3 036/135] idr: Fix idr_get_next_ul race with idr_remove

Greg Kroah-Hartman
2019-12-03T22:40:46Z

From: Matthew Wilcox (Oracle) <willy@infradead.org>

[ Upstream commit 5a74ac4c4a97bd8b7dba054304d598e2a882fea6 ]

Commit 5c089fd0c734 ("idr: Fix idr_get_next race with idr_remove")
neglected to fix idr_get_next_ul(). As far as I can tell, nobody's
actually using this interface under the RCU read lock, but fix it now
before anybody decides to use it.

Fixes: 5c089fd0c734 ("idr: Fix idr_get_next race with idr_remove")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/idr.c | 31 +++++++++++--------------------
1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/lib/idr.c b/lib/idr.c
index 66a3748924828..c2cf2c52bbde5 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -215,7 +215,7 @@ int idr_for_each(const struct idr *idr,
EXPORT_SYMBOL(idr_for_each);

/**
- * idr_get_next() - Find next populated entry.
+ * idr_get_next_ul() - Find next populated entry.
* @idr: IDR handle.
* @nextid: Pointer to an ID.
*
@@ -224,7 +224,7 @@ EXPORT_SYMBOL(idr_for_each);
* to the ID of the found value. To use in a loop, the value pointed to by
* nextid must be incremented by the user.
*/
-void *idr_get_next(struct idr *idr, int *nextid)
+void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
{
struct radix_tree_iter iter;
void __rcu **slot;
@@ -245,18 +245,14 @@ void *idr_get_next(struct idr *idr, int *nextid)
}
if (!slot)
return NULL;
- id = iter.index + base;
-
- if (WARN_ON_ONCE(id > INT_MAX))
- return NULL;

- *nextid = id;
+ *nextid = iter.index + base;
return entry;
}
-EXPORT_SYMBOL(idr_get_next);
+EXPORT_SYMBOL(idr_get_next_ul);

/**
- * idr_get_next_ul() - Find next populated entry.
+ * idr_get_next() - Find next populated entry.
* @idr: IDR handle.
* @nextid: Pointer to an ID.
*
@@ -265,22 +261,17 @@ EXPORT_SYMBOL(idr_get_next);
* to the ID of the found value. To use in a loop, the value pointed to by
* nextid must be incremented by the user.
*/
-void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
+void *idr_get_next(struct idr *idr, int *nextid)
{
- struct radix_tree_iter iter;
- void __rcu **slot;
- unsigned long base = idr->idr_base;
unsigned long id = *nextid;
+ void *entry = idr_get_next_ul(idr, &id);

- id = (id < base) ? 0 : id - base;
- slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
- if (!slot)
+ if (WARN_ON_ONCE(id > INT_MAX))
return NULL;
-
- *nextid = iter.index + base;
- return rcu_dereference_raw(*slot);
+ *nextid = id;
+ return entry;
}
-EXPORT_SYMBOL(idr_get_next_ul);
+EXPORT_SYMBOL(idr_get_next);

/**
* idr_replace() - replace pointer for given ID.
--
2.20.1