2021-12-26 10:26:40

by SeongJae Park

Subject: [PATCH] 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]
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(+)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index f94d19a690df..d3bc110430f9 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -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;
}

--
2.17.1

2021-12-27 12:35:50

by Greg Kroah-Hartman

Subject: Re: [PATCH] mm/damon/dbgfs: protect targets destructions with kdamond_lock

On Sun, Dec 26, 2021 at 10:26:32AM +0000, SeongJae Park wrote:
> 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]
> 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.

Now queued up, thanks.

greg k-h