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b=Q1Seo8Ffs3lw+ArmCzrhd6+ZuK+vKuYMzCkkcKrKjxwuJT0X3+DzQ2Awmfl08SI72 pIaCRoLbGkSpScHQFf3cHZXrZE7SX8T6cbsPSJsSdCA7QOZOubFE3WbK9N5Xuflktj AUJUIUfPmRsOkDNkIW5rAeKIPjhWe6T3AqAhXhyUDW3MKKKBHcUL5Zn9r+nkRAKn8a cz2W203yWDri1oey6bDLcrkSeF3Qd4TFZcPAaHcbpp/K617KHHh/uLB6HIqMIxCDeR aePKtHaldDnUpqJJIdXc+G7FPb6/UPvk5ym6qX9YRCVuERqhXrbxn4qBoJd4AWPoOe owd+xm28QDkmA== From: SJ Park To: SJ Park Cc: Andrew Morton , Yang Yingliang , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/damon/core: validate ranges in damon_set_regions() Date: Mon, 29 Jun 2026 21:26:12 -0700 Message-ID: <20260630042612.151351-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260630035221.146458-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: uhg9ay6p8jndz48ezuf46rk84hgzby9n X-Rspamd-Queue-Id: 2C97D100002 X-Rspamd-Server: rspam06 X-HE-Tag: 1782793584-976106 X-HE-Meta: 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 Fs8jUzzm 501Fk8RQB8l4/VE6zcoCMuPBCx9YeelbXVWNLLQTy1D1cO5Z8CngX3rlmPwjBAE7zDc/y5wcxuNw+7fHZzhqGMcGKpQO7L8v8eDOCU72kub6izRfgTNmbwWYHePIL6itXj9SwMxpmF+zdh5vbEg872nr/a5V1dFNW6naCh/ZbNZNh/4jzW3+cvgIReGmUxBAx9W1P6e4wLs68p8bGsORlra32m9SkuZrbdMPKlk5LUMBWzWV2OtmKID9GV3yFbLEBN+/MySZkHfyhX4VWrVkFKjQvvw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 29 Jun 2026 20:52:19 -0700 SJ Park wrote: > DAMON core logic assumes zero length regions don't exist. However, a > few DAMON API callers including DAMON_SYSFS, DAMON_RECLAIM and > DAMON_LRU_SORT allow users to set empty monitoring target regions. This > could result in WARN_ONCE() on CONFIG_DAMON_DEBUG_SANITY enabled kernel, > and divide-by-zero from damon_merge_two_regions(). > > For example, the WANR_ONCE() can be triggered like below. > > # grep DAMON_DEBUG_SANITY /boot/config-$(uname -r) > # CONFIG_DAMON_DEBUG_SANITY=y > # damo start > # cd /sys/kernel/mm/damon/admin/kdamonds/0 > # echo 0 > contexts/0/targets/0/regions/0/start > # echo 0 > contexts/0/targets/0/regions/0/end > # echo commit > state > # dmesg > [....] > [ 73.705780] ------------[ cut here ]------------ > [ 73.707552] start 0 >= end 0 > [ 73.708452] WARNING: mm/damon/core.c:359 at damon_new_region+0x6e/0x80, CPU#1: kdamond.0/758 > [...] > > All DAMON API callers eventually use damon_set_regions() to setup the > regions. Add the validation logic in the function. Sashiko found a pre-existing issue, and it is not a blocker of this patch in my opinion. Read my reply [1] to Sashiko review for more details. So this patch is good to go. [1] https://lore.kernel.org/20260630041806.151124-1-sj@kernel.org Thanks, SJ [...]