[PATCH 2/8] idr: fix unexpected id-removal when idr_remove(unallocated_id)

[Lai Jiangshan]

If unallocated_id = (ANY * idr_max(idp->layers) + existed_id) is passed
to idr_remove(). The existed_id will be removed unexpected.

The following test shows this unexpected id-removal:

static void test4(void)
{
	int id;
	DEFINE_IDR(test_idr);

	printk(KERN_INFO "Start test4\n");
	id = idr_alloc(&test_idr, (void *)1, 42, 43, GFP_KERNEL);
	BUG_ON(id != 42);
	idr_remove(&test_idr, 42 + IDR_SIZE);
	TEST_BUG_ON(idr_find(&test_idr, 42) != (void *)1);
	idr_destroy(&test_idr);
	printk(KERN_INFO "End of test4\n");
}

It only happens when unallocated_id, it is caller's fault. It is not
a bug. But it is better to add the proper check and complains instead
of removing an existed_id silently.

Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
 lib/idr.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/lib/idr.c b/lib/idr.c
index 4df6792..a28036d 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -562,6 +562,11 @@ void idr_remove(struct idr *idp, int id)
 	if (id < 0)
 		return;
 
+	if (id > idr_max(idp->layers)) {
+		idr_remove_warning(id);
+		return;
+	}
+
 	sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
 	if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
 	    idp->top->ary[0]) {
-- 
1.7.4.4

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