Re: [PATCH 0/4] mm/damon/sysfs: fix resource leak and NULL pointer dereferences

Josh Law
2026-03-19T19:24:25Z

On 19 March 2026 15:57:38 GMT, Josh Law <objecting@objecting.org> wrote:
>This series fixes a memory leak and three NULL pointer dereferences in
>the DAMON sysfs interface, all in mm/damon/sysfs.c.
>
>Patch 1 fixes a damon_ctx leak in damon_sysfs_commit_input() when
>damon_sysfs_new_test_ctx() fails after param_ctx was already built.
>
>Patches 2-4 fix missing contexts->nr checks before dereferencing
>contexts_arr[0]. A user can trigger these by setting nr_contexts to 0
>via sysfs and then issuing commands that assume a context exists:
>
> - Patch 2: CLEAR_SCHEMES_TRIED_REGIONS handler in damon_sysfs_handle_cmd()
> - Patch 3: damon_sysfs_update_schemes_tried_regions(), reached via
> UPDATE_SCHEMES_TRIED_BYTES and UPDATE_SCHEMES_TRIED_REGIONS
> - Patch 4: damon_sysfs_repeat_call_fn(), reachable when nr_contexts is
> set to 0 while DAMON is running
>
>Josh Law (4):
> mm/damon/sysfs: fix param_ctx leak on damon_sysfs_new_test_ctx()
> failure
> mm/damon/sysfs: check contexts->nr before clear_schemes_tried_regions
> mm/damon/sysfs: check contexts->nr in update_schemes_tried_regions
> mm/damon/sysfs: check contexts->nr in repeat_call_fn
>
> mm/damon/sysfs.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>

[0] <https://sashiko.dev/#/patchset/20260319155742.186627-1-objecting%40objecting.org>

I don't think this is right. Probably best you don't listen to that..

V/R

Josh Law