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mm/damon/dbgfs: protect targets destructions with kdamond_lock

PATCH In review SeongJae Park 2 participants 2 messages Dec 26, 2021 – Dec 27, 2021

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Stable branch Memory management DAMON
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SeongJae Park

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PATCH 1/1 mm/damon/dbgfs: protect targets destructions with kdamond_lock

commit 34796417964b8d0aef45a99cf6c2d20cebe33733 upstream.

DAMON debugfs interface iterates current monitoring targets in 'dbgfs_target_ids_read()' while holding the corresponding 'kdamond_lock'. However, it also destructs the monitoring targets in 'dbgfs_before_terminate()' without holding the lock. This can result in a use_after_free bug. This commit avoids the race by protecting the destruction with the corresponding 'kdamond_lock'.

Link https://lkml.kernel.org/r/[email protected] open here
Reported-by Sangwoo Bae <[email protected]>
Fixes 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by SeongJae Park <[email protected]>
Cc <[email protected]> # 5.15.x
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>

---
This is a backport of a DAMON fix that merged in the mainline, for v5.15.x stable series.

 mm/damon/dbgfs.c | 2 ++
 1 file changed, 2 insertions(+)
mm/damon/dbgfs.c +2 -0
index f94d19a690df..d3bc110430f9 100644
@@ -309,10 +309,12 @@ static int dbgfs_before_terminate(struct damon_ctx *ctx)
 	if (!targetid_is_pid(ctx))
 		return 0;
 
+	mutex_lock(&ctx->kdamond_lock);
 	damon_for_each_target_safe(t, next, ctx) {
 		put_pid((struct pid *)t->id);
 		damon_destroy_target(t);
 	}
+	mutex_unlock(&ctx->kdamond_lock);
 	return 0;
 }
Signature · 1 line
2.17.1
maintainer
#1 lore raw
Quoted 16 lines · SeongJae Park

commit 34796417964b8d0aef45a99cf6c2d20cebe33733 upstream.

DAMON debugfs interface iterates current monitoring targets in 'dbgfs_target_ids_read()' while holding the corresponding 'kdamond_lock'. However, it also destructs the monitoring targets in 'dbgfs_before_terminate()' without holding the lock. This can result in a use_after_free bug. This commit avoids the race by protecting the destruction with the corresponding 'kdamond_lock'.

Link https://lkml.kernel.org/r/[email protected] open here
Reported-by Sangwoo Bae <[email protected]>
Fixes 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by SeongJae Park <[email protected]>
Cc <[email protected]> # 5.15.x
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
Quoted 3 lines

---
This is a backport of a DAMON fix that merged in the mainline, for v5.15.x stable series.

Now queued up, thanks.

greg k-h