From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794167515; b=bFWBOnenZJbk5pjY+TOD1jVwUr4EmyuIS2YPA2Z8/f+GHtd0aODLjXc1d7eUzRoqAy7A DPLZXPruZQRUqcUXZejWrZuaeqJiOk+A+GEpkHTwrOfctk8XxdjkkbMBqG7mnnnBbwnkm RF/1dMDm+qC+8u1XpsXnzMBRgfyQLYePHyP5Ylfg6JcWEp4w6LLDSiUH/CSTDR/oeWz77 om59k+/rLmVXg/oIGeOIAtjjeWNPRk5mahpbw2vqyYeM3TZyhkJif6DFtoxChEcTnSN9Z BFwK7QkF6waC7vME4frVitA0fVKXvOn6FyEO7bnTWaVHpfDucM4cOj5JZni8yP48ZCQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794167515; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=nyCIxBA5mJ06vHi0FAU5PamOp23wz03gHLUhBxnc4Z0=; b=Tax1J5vcmfJnxCu4te1bKWdvfKp1ZBe7v8dLdtoikVpkrLEZgVitGSNGEvEcv1E4FKqx nWV1NBmY/RqMFXWtTJE+44CeW8De6WHSFY3atgxxUhEw1mxPylbaeTY52+3W7+OULT0Jl R2yIXgKMyyBh/rG4ymEP6Zd5rLsK59jhsFCwVfZPozxkLKOUfTnSv4mWcZ2UaNhoWgY/i J1ukHGu8/bFBiHvkT81GV9oguygjqeit9eJMBV6fryQQt1GHdWaBqL3tqAj7msu+gWcuc LeWBM+7ritrkaKkwlqjVghKvea/+8mUX1NiR171A1ZNAk2L5MmssLb8vF1/Zbf2OFLw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=bCCmMKr9; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F195606D807; Sun, 8 Nov 2026 19:51:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=bCCmMKr9 Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1E731F0089F; Sun, 8 Nov 2026 19:51:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794167515; bh=nyCIxBA5mJ06vHi0FAU5PamOp23wz03gHLUhBxnc4Z0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bCCmMKr9mWEtSu9yXIOOi9024KfSuJI6gvjZHyavY7QB+O+I5HT6h5lfD175ScXRy iKq6I3GjHY7l1fFMTudDAafB99NVtgyuO4gOEFAcM41RCPulUtCeufn+F8TOHyxl51 F/RclWBx0uvEn6g5F1DF52S3wizQ6A+1tvT53g99Em98W9123aIX+YBv/QBejczDQ7 XLJNJHy/+sp1ATuOVr2k/YDEptTrKVl+8wnnqQKP05P5Ac/47PHjk67fGYEzldFw7W HIrgmsFRAoLKKJwtLTN8S+4+qPNUc/Mk7ToW/4gxoaWTOLA8VYNTv2YZPjNCnmSxuB FwpePQint3PPA== From: SJ Park To: stable@vger.kernel.org Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 6.12.y 4/5] mm/damon/core: filter out damos address filter-split failed region Date: Sun, 8 Nov 2026 11:51:43 -0800 Message-ID: <20261108195145.115792-5-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261108195145.115792-1-sj@kernel.org> References: <20261108195145.115792-1-sj@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When an address type DAMOS filter is configured, DAMOS tries to split the region for the filter range, and apply DAMOS action to the filter-in region. The split operation (damon_split_region_at()) could fail from allocation failure under extreme memory pressure. In the case, DAMOS action could be applied more or less than expected, ignoring the address filter. The issue only rarely happens under extreme memory pressure. No crash or leak happens. Occasionally not applying the action to a few regions shouldn't be a real problem. But applying the action to a region that the user has excluded via address filter could be a surprise depending on the use case. It is only theoretical. No such real case is found yet. Filter out the entire region if the split is failed. Update damos_filter_match() signature to receive the error from split. Also update kunit tests for the updated signature. The issue was discovered [1] by sashiko. Link: https://lore.kernel.org/20261020004119.106690-1-sj@kernel.org Link: https://lore.kernel.org/20260801203121.117449-1-sj@kernel.org [1] Fixes: ab9bda001b68 ("mm/damon/core: introduce address range type damos filter") Signed-off-by: SJ Park Signed-off-by: Andrew Morton Cc: # 6.6.x (cherry picked from commit bbeec2d8324d7aac438bb12dd2d22b184e0a8d43) Signed-off-by: SJ Park --- mm/damon/core.c | 13 +++++++++---- mm/damon/tests/core-kunit.h | 11 ++++++----- 2 files changed, 15 insertions(+), 9 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 52f01a6508b66..046c07b86a6e7 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1372,13 +1372,14 @@ static void damos_update_stat(struct damos *s, } static bool __damos_filter_out(struct damon_ctx *ctx, struct damon_target *t, - struct damon_region *r, struct damos_filter *filter) + struct damon_region *r, struct damos_filter *filter, int *err) { bool matched = false; struct damon_target *ti; int target_idx = 0; unsigned long start, end; + *err = 0; switch (filter->type) { case DAMOS_FILTER_TYPE_TARGET: damon_for_each_target(ti, ctx) { @@ -1404,12 +1405,13 @@ static bool __damos_filter_out(struct damon_ctx *ctx, struct damon_target *t, } /* start before the range and overlap */ if (r->ar.start < start) { - damon_split_region_at(t, r, start - r->ar.start); + *err = damon_split_region_at(t, r, + start - r->ar.start); matched = false; break; } /* start inside the range */ - damon_split_region_at(t, r, end - r->ar.start); + *err = damon_split_region_at(t, r, end - r->ar.start); matched = true; break; default: @@ -1423,9 +1425,12 @@ static bool damos_filter_out(struct damon_ctx *ctx, struct damon_target *t, struct damon_region *r, struct damos *s) { struct damos_filter *filter; + bool matching; + int err; damos_for_each_filter(filter, s) { - if (__damos_filter_out(ctx, t, r, filter)) + matching = __damos_filter_out(ctx, t, r, filter, &err); + if (matching || err) return true; } return false; diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h index ff9f73579f7b3..6b7cd8149a0e2 100644 --- a/mm/damon/tests/core-kunit.h +++ b/mm/damon/tests/core-kunit.h @@ -527,6 +527,7 @@ static void damos_test_filter_out(struct kunit *test) struct damon_target *t; struct damon_region *r, *r2; struct damos_filter *f; + int err; f = damos_new_filter(DAMOS_FILTER_TYPE_ADDR, true); f->addr_range = (struct damon_addr_range){ @@ -537,25 +538,25 @@ static void damos_test_filter_out(struct kunit *test) damon_add_region(r, t); /* region in the range */ - KUNIT_EXPECT_TRUE(test, __damos_filter_out(NULL, t, r, f)); + KUNIT_EXPECT_TRUE(test, __damos_filter_out(NULL, t, r, f, &err)); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); /* region before the range */ r->ar.start = DAMON_MIN_REGION * 1; r->ar.end = DAMON_MIN_REGION * 2; - KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f)); + KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f, &err)); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); /* region after the range */ r->ar.start = DAMON_MIN_REGION * 6; r->ar.end = DAMON_MIN_REGION * 8; - KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f)); + KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f, &err)); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); /* region started before the range */ r->ar.start = DAMON_MIN_REGION * 1; r->ar.end = DAMON_MIN_REGION * 4; - KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f)); + KUNIT_EXPECT_FALSE(test, __damos_filter_out(NULL, t, r, f, &err)); /* filter should have split the region */ KUNIT_EXPECT_EQ(test, r->ar.start, DAMON_MIN_REGION * 1); KUNIT_EXPECT_EQ(test, r->ar.end, DAMON_MIN_REGION * 2); @@ -570,7 +571,7 @@ static void damos_test_filter_out(struct kunit *test) /* region started in the range */ r->ar.start = DAMON_MIN_REGION * 2; r->ar.end = DAMON_MIN_REGION * 8; - KUNIT_EXPECT_TRUE(test, __damos_filter_out(NULL, t, r, f)); + KUNIT_EXPECT_TRUE(test, __damos_filter_out(NULL, t, r, f, &err)); /* filter should have split the region */ KUNIT_EXPECT_EQ(test, r->ar.start, DAMON_MIN_REGION * 2); KUNIT_EXPECT_EQ(test, r->ar.end, DAMON_MIN_REGION * 6); -- 2.47.3