This is a note to let you know that I've just added the patch titled idr test suite: Take RCU read lock in idr_find_test_1 to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: idr-test-suite-take-rcu-read-lock-in-idr_find_test_1.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit ab5557a6c4bb9abd096b840b3cb79839abf96717 Author: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Date: Thu Apr 1 07:44:48 2021 -0400 idr test suite: Take RCU read lock in idr_find_test_1 [ Upstream commit 703586410da69eb40062e64d413ca33bd735917a ] When run on a single CPU, this test would frequently access already-freed memory. Due to timing, this bug never showed up on multi-CPU tests. Reported-by: Chris von Recklinghausen <crecklin@xxxxxxxxxx> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/tools/testing/radix-tree/idr-test.c b/tools/testing/radix-tree/idr-test.c index 44ceff95a9b3..4a9b451b7ba0 100644 --- a/tools/testing/radix-tree/idr-test.c +++ b/tools/testing/radix-tree/idr-test.c @@ -306,11 +306,15 @@ void idr_find_test_1(int anchor_id, int throbber_id) BUG_ON(idr_alloc(&find_idr, xa_mk_value(anchor_id), anchor_id, anchor_id + 1, GFP_KERNEL) != anchor_id); + rcu_read_lock(); do { int id = 0; void *entry = idr_get_next(&find_idr, &id); + rcu_read_unlock(); BUG_ON(entry != xa_mk_value(id)); + rcu_read_lock(); } while (time(NULL) < start + 11); + rcu_read_unlock(); pthread_join(throbber, NULL);