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Thu, 19 Mar 2026 16:57:45 +0100 (CET) From: Josh Law To: sj@kernel.org, akpm@linux-foundation.org Cc: damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Law Subject: [PATCH 3/4] mm/damon/sysfs: check contexts->nr in update_schemes_tried_regions Date: Thu, 19 Mar 2026 15:57:41 +0000 Message-Id: <20260319155742.186627-4-objecting@objecting.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260319155742.186627-1-objecting@objecting.org> References: <20260319155742.186627-1-objecting@objecting.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-ZohoMailClient: External X-Rspam-User: X-Stat-Signature: a54n9htph31ty5pn7xqc5ytcb44smfgm X-Rspamd-Queue-Id: 65C501C000E X-Rspamd-Server: rspam03 X-HE-Tag: 1773935877-132061 X-HE-Meta: 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 pN58n54F gyRwwc+JwLzgA9KMSHzL7K6HJwWQIiMcxX5aoutKn8afeUtia+tPlxewpQDuRhEFmPodED/o2AbKVWZaXr+vtMlyRvyQj5x57tt5Bv+/wtXZgtXbb9gi4R8GQ8LcoppOkx7rtES65Ld1MipwaaEl7l+DB3CVppibpoLATL8at9L6q5qlGZpsWRI1OGiyEw1BRM13Q/wrL77VoRjkn4Sfb0daEblOFRdEg3mJQOZps6ymCdkDs5wtCAU02lIxSyFFLGcIlT3uvHfPlxherB/exLPTkz+QnXZ1WfmGZvtk2pQxNKrBJFzL9fzHGzKm4yNExd3HsoI4zlKyp0urW4kyr7rRB6O9X0kGnFdtUtFuOzm342pItgoSj+bTpSvv/pFlnnXdiyw4KxusMRFFWKQ4kpRqUJ2ZG/iN7cmKQoMUIBmozxvU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: damon_sysfs_update_schemes_tried_regions() and its callback damon_sysfs_schemes_tried_regions_upd_one() access contexts_arr[0] without verifying nr_contexts >= 1. This can NULL deref if damon_ctx is non-NULL (preserved after stop) but nr_contexts has been set to 0. Add the missing check. Signed-off-by: Josh Law --- mm/damon/sysfs.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index 36ad2e8956c9..ddcdc4e35b27 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1731,6 +1731,8 @@ static int damon_sysfs_update_schemes_tried_regions( if (!ctx) return -EINVAL; + if (sysfs_kdamond->contexts->nr != 1) + return -EINVAL; damon_sysfs_schemes_clear_regions( sysfs_kdamond->contexts->contexts_arr[0]->schemes); -- 2.34.1