[PATCH AUTOSEL 6.1 1/2] locking/ww_mutex/test: Fix potential workqueue corruption

[PATCH AUTOSEL 6.1 1/2] locking/ww_mutex/test: Fix potential workqueue corruption

[Sasha Levin]

From: John Stultz <jstultz@google.com>

[ Upstream commit bccdd808902f8c677317cec47c306e42b93b849e ]

In some cases running with the test-ww_mutex code, I was seeing
odd behavior where sometimes it seemed flush_workqueue was
returning before all the work threads were finished.

Often this would cause strange crashes as the mutexes would be
freed while they were being used.

Looking at the code, there is a lifetime problem as the
controlling thread that spawns the work allocates the
"struct stress" structures that are passed to the workqueue
threads. Then when the workqueue threads are finished,
they free the stress struct that was passed to them.

Unfortunately the workqueue work_struct node is in the stress
struct. Which means the work_struct is freed before the work
thread returns and while flush_workqueue is waiting.

It seems like a better idea to have the controlling thread
both allocate and free the stress structures, so that we can
be sure we don't corrupt the workqueue by freeing the structure
prematurely.

So this patch reworks the test to do so, and with this change
I no longer see the early flush_workqueue returns.

Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230922043616.19282-3-jstultz@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/locking/test-ww_mutex.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 43efb2a041602..b1e25695185a4 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -466,7 +466,6 @@ static void stress_inorder_work(struct work_struct *work)
 	} while (!time_after(jiffies, stress->timeout));
 
 	kfree(order);
-	kfree(stress);
 }
 
 struct reorder_lock {
@@ -531,7 +530,6 @@ static void stress_reorder_work(struct work_struct *work)
 	list_for_each_entry_safe(ll, ln, &locks, link)
 		kfree(ll);
 	kfree(order);
-	kfree(stress);
 }
 
 static void stress_one_work(struct work_struct *work)
@@ -552,8 +550,6 @@ static void stress_one_work(struct work_struct *work)
 			break;
 		}
 	} while (!time_after(jiffies, stress->timeout));
-
-	kfree(stress);
 }
 
 #define STRESS_INORDER BIT(0)
@@ -564,15 +560,24 @@ static void stress_one_work(struct work_struct *work)
 static int stress(int nlocks, int nthreads, unsigned int flags)
 {
 	struct ww_mutex *locks;
-	int n;
+	struct stress *stress_array;
+	int n, count;
 
 	locks = kmalloc_array(nlocks, sizeof(*locks), GFP_KERNEL);
 	if (!locks)
 		return -ENOMEM;
 
+	stress_array = kmalloc_array(nthreads, sizeof(*stress_array),
+				     GFP_KERNEL);
+	if (!stress_array) {
+		kfree(locks);
+		return -ENOMEM;
+	}
+
 	for (n = 0; n < nlocks; n++)
 		ww_mutex_init(&locks[n], &ww_class);
 
+	count = 0;
 	for (n = 0; nthreads; n++) {
 		struct stress *stress;
 		void (*fn)(struct work_struct *work);
@@ -596,9 +601,7 @@ static int stress(int nlocks, int nthreads, unsigned int flags)
 		if (!fn)
 			continue;
 
-		stress = kmalloc(sizeof(*stress), GFP_KERNEL);
-		if (!stress)
-			break;
+		stress = &stress_array[count++];
 
 		INIT_WORK(&stress->work, fn);
 		stress->locks = locks;
@@ -613,6 +616,7 @@ static int stress(int nlocks, int nthreads, unsigned int flags)
 
 	for (n = 0; n < nlocks; n++)
 		ww_mutex_destroy(&locks[n]);
+	kfree(stress_array);
 	kfree(locks);
 
 	return 0;
-- 
2.42.0

[PATCH AUTOSEL 6.1 2/2] lib/generic-radix-tree.c: Don't overflow in peek()

[Sasha Levin]

From: Kent Overstreet <kent.overstreet@gmail.com>

[ Upstream commit 9492261ff2460252cf2d8de89cdf854c7e2b28a0 ]

When we started spreading new inode numbers throughout most of the 64
bit inode space, that triggered some corner case bugs, in particular
some integer overflows related to the radix tree code. Oops.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/generic-radix-tree.h |  7 +++++++
 lib/generic-radix-tree.c           | 17 ++++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/include/linux/generic-radix-tree.h b/include/linux/generic-radix-tree.h
index 107613f7d7920..f6cd0f909d9fb 100644
--- a/include/linux/generic-radix-tree.h
+++ b/include/linux/generic-radix-tree.h
@@ -38,6 +38,7 @@
 
 #include <asm/page.h>
 #include <linux/bug.h>
+#include <linux/limits.h>
 #include <linux/log2.h>
 #include <linux/math.h>
 #include <linux/types.h>
@@ -184,6 +185,12 @@ void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t);
 static inline void __genradix_iter_advance(struct genradix_iter *iter,
 					   size_t obj_size)
 {
+	if (iter->offset + obj_size < iter->offset) {
+		iter->offset	= SIZE_MAX;
+		iter->pos	= SIZE_MAX;
+		return;
+	}
+
 	iter->offset += obj_size;
 
 	if (!is_power_of_2(obj_size) &&
diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c
index f25eb111c0516..7dfa88282b006 100644
--- a/lib/generic-radix-tree.c
+++ b/lib/generic-radix-tree.c
@@ -166,6 +166,10 @@ void *__genradix_iter_peek(struct genradix_iter *iter,
 	struct genradix_root *r;
 	struct genradix_node *n;
 	unsigned level, i;
+
+	if (iter->offset == SIZE_MAX)
+		return NULL;
+
 restart:
 	r = READ_ONCE(radix->root);
 	if (!r)
@@ -184,10 +188,17 @@ void *__genradix_iter_peek(struct genradix_iter *iter,
 			(GENRADIX_ARY - 1);
 
 		while (!n->children[i]) {
+			size_t objs_per_ptr = genradix_depth_size(level);
+
+			if (iter->offset + objs_per_ptr < iter->offset) {
+				iter->offset	= SIZE_MAX;
+				iter->pos	= SIZE_MAX;
+				return NULL;
+			}
+
 			i++;
-			iter->offset = round_down(iter->offset +
-					   genradix_depth_size(level),
-					   genradix_depth_size(level));
+			iter->offset = round_down(iter->offset + objs_per_ptr,
+						  objs_per_ptr);
 			iter->pos = (iter->offset >> PAGE_SHIFT) *
 				objs_per_page;
 			if (i == GENRADIX_ARY)
-- 
2.42.0