In idr_replace(), when the top layer is the max-high layer(p->layer == 3),
The "(1 << n)" will overflow and the result is 0, it causes idr_replace()
return -EINVAL even the id is actually valid.
The following test code shows it fails to replace the value for id=((1<<27)+42):
static void test5(void)
{
int id;
DEFINE_IDR(test_idr);
#define TEST5_START ((1<<27)+42) /* use the highest layer */
printk(KERN_INFO "Start test5\n");
id = idr_alloc(&test_idr, (void *)1, TEST5_START, 0, GFP_KERNEL);
BUG_ON(id != TEST5_START);
TEST_BUG_ON(idr_replace(&test_idr, (void *)2, TEST5_START) != (void *)1);
idr_destroy(&test_idr);
printk(KERN_INFO "End of test5\n");
}
Fixed the bug by using idr_max() instead of the incorrect open code.
There is the same problem in sub_alloc(). The overflow causes sub_alloc()
returns -EAGAIN unexpectedly. But the idr_get_empty_slot() will call it
again with increased @id. So the bug is hided.
CC: stable@xxxxxxxxxxxxxxx
Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
lib/idr.c | 8 +++-----
1 files changed, 3 insertions(+), 5 deletions(-)
diff --git a/lib/idr.c b/lib/idr.c
index 2642fa8..4df6792 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -249,7 +249,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa,
id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
/* if already at the top layer, we need to grow */
- if (id >= 1 << (idp->layers * IDR_BITS)) {
+ if (id > idr_max(idp->layers)) {
*starting_id = id;
return -EAGAIN;
}
@@ -811,12 +811,10 @@ void *idr_replace(struct idr *idp, void *ptr, int id)
if (!p)
return ERR_PTR(-EINVAL);
- n = (p->layer+1) * IDR_BITS;
-
- if (id >= (1 << n))
+ if (id > idr_max(p->layer + 1))
return ERR_PTR(-EINVAL);
- n -= IDR_BITS;
+ n = p->layer * IDR_BITS;
while ((n > 0) && p) {
p = p->ary[(id >> n) & IDR_MASK];
n -= IDR_BITS;
--
1.7.4.4
--
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