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5adaaa28be
damon_sysfs_apply_inputs() reads ops_id twice. It could race with
ops_id_store(). As a result, the min_region_sz could wrongly be set up.
Read it once.
The user impact is trivial. Sane users ain't update the parameter in
parallel. Even if it happens, the DAMON core layer handles the wrong
min_region_sz (!is_power_of_2()). Even if somehow the race ended up
making a min_region_sz that is different from the user's intention but
still valid, only monitoring itself runs differently than expected. No
critical consequences like kernel panic or memory corruption happen
The issue was discovered [1] by Sashiko.
Link: https://lore.kernel.org/20260715031002.108504-7-sj@kernel.org
Link: https://lore.kernel.org/20260703172417.95426-1-sj@kernel.org [1]
Fixes: 8d009da32f ("mm/damon/sysfs: set damon_ctx->min_sz_region only for paddr use case")
Signed-off-by: SJ Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 6.18.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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