idr: fix obscure bug in allocation path (7aae6dd8) · Commits · 戴 / test

In sub_alloc(), when bitmap search fails, it goes up one level to continue search. This is done by updating the id cursor and searching the upper level again. If the cursor was at the end of the upper level, we need to go further than that. This wasn't implemented and when that happens the part of the cursor which indexes into the upper level wraps and sub_alloc() ends up searching the wrong bitmap. It allocates id which doesn't match the actual slot. This patch fixes this by restarting from the top if the search needs to go higher than one level. Signed-off-by:

Tejun Heo <htejun@gmail.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@suse.de>

lib/idr.c

+14 −2

Original line number	Diff line number	Diff line
		@@ -100,10 +100,11 @@ static int sub_alloc(struct idr idp, void ptr, int *starting_id)
		int n, m, sh;
		struct idr_layer p, new;
		struct idr_layer *pa[MAX_LEVEL];
		int l, id;
		int l, id, oid;
		long bm;

		id = *starting_id;
		restart:
		p = idp->top;
		l = idp->layers;
		pa[l--] = NULL;
		@@ -117,12 +118,23 @@ static int sub_alloc(struct idr idp, void ptr, int *starting_id)
		if (m == IDR_SIZE) {
		/* no space available go back to previous layer. */
		l++;
		oid = id;
		id = (id \| ((1 << (IDR_BITS * l)) - 1)) + 1;

		/* if already at the top layer, we need to grow */
		if (!(p = pa[l])) {
		*starting_id = id;
		return -2;
		}

		/* If we need to go up one layer, continue the
		* loop; otherwise, restart from the top.
		*/
		sh = IDR_BITS * (l + 1);
		if (oid >> sh == id >> sh)
		continue;
		else
		goto restart;
		}
		if (m != n) {
		sh = IDR_BITS*l;

Admin message