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authorLai Jiangshan <laijs@cn.fujitsu.com>2014-06-06 21:37:10 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-06 23:08:12 (GMT)
commit3afb69cb5572b3c8c898c00880803cf1a49852c4 (patch)
tree565e9e1e1ba653ae7a45eb3e55aa68e9bfb3bd87 /lib/idr.c
parente1bebcf41ed0aa15f11cec186cbd5141730bcafc (diff)
idr: fix overflow bug during maximum ID calculation at maximum height
idr_replace() open-codes the logic to calculate the maximum valid ID given the height of the idr tree; unfortunately, the open-coded logic doesn't account for the fact that the top layer may have unused slots and over-shifts the limit to zero when the tree is at its maximum height. 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"); } Fix the bug by using idr_max() which correctly takes into account the maximum allowed shift. sub_alloc() shares the same problem and may incorrectly fail with -EAGAIN; however, this bug doesn't affect correct operation because idr_get_empty_slot(), which already uses idr_max(), retries with the increased @id in such cases. [tj@kernel.org: Updated patch description.] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/idr.c')
-rw-r--r--lib/idr.c8
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;

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