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=1794082212; b=ECUcdk5zigDWCyOWLztGwZCRqrNch4k6Fb+hGKHnyRAWf/IgW8WRwCO2ishv4BDlJJUz Ho/3xRIyPeUAV+iQUpvtj0/sSKgnem11QvbB3YXk0ZSkJ3g6bCO0PRK+ofURFLMfPv4n3 eerttzTBqO5y/m3tNIYwShUYG0b0UcBTbmQrc3v1QTLZpYG6INua2y/zrzkWK3mEs4Tcs Zvcu2gr1b17l6yvcR5e4F1gNNyXFiptw9I/1epN4QpAsrg1R2auFFif+sL2laPJwWexbM BADzIKCAEsdApGTjkzR19bL6ixZ3FSDw5cRonzNTu9LpQDsWBlpvAIT3LdLHwkTzllA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794082212; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=TIAVWRl5IyIEzSAGdy1Y9O94fKWUT6y4xqwWabU5n+M=; b=2XuWxx5f+Ze8584V4X7b11qXrP1/hd6ZwGnnKcerjUo/G0AySs/evCuVUtBV0z5/bTZp VPaSnTs1k8zjQRTQzr/RSE4xI0ewmxnFWEj95XX7qZ1/Ef3F+RxaoiwldcEC/6OD4eIW5 O+UPiUaOtCcsPLGdobtIFeCPKQ9hyiwAlAJgy4Sh78BSiklKWKoXxw/i2t8aelwODg4oS CSgcu73XTCZtrodjfcb7LfJjiVfdDUixPMVZRTsHrsNuqZbLby4fUUpmba8/nwAXItXSP URkzCjSuB6bGhd1h/byZs+zc3G3U8YPLQjZKcfbmGq+x+mw8ZqbPV8cMn1d1e8ylvmQ== 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=LPjsm0m9; 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 A36B3606D82B; Sat, 7 Nov 2026 20:10:11 +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=LPjsm0m9 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4DF501F008AB; Sat, 7 Nov 2026 20:10:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794082211; bh=TIAVWRl5IyIEzSAGdy1Y9O94fKWUT6y4xqwWabU5n+M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LPjsm0m9nACOdC0KAk8ANoS9Ly8u0kM51qmquHDqDhuZLfKLwr0Q2z+iSYMtsUHwd hlRiCO4hNc2UxC0daRQWjOhW3r3CSX/Wxl8FLRhB8yi/92VZs1S5sfwbdoIUgkKCEo Loc4iyzPizp6Ny1ISQiSKE+WeF7mKUVsQ8scyNMhlvxSTpgHrg9ZPEPrhjs8cO7uYj TNk6Ls8ow1sOBcwuevAjSVsf9t81VnW/uKpJjlFaMi1g3ov/m1Dsa+WPMQ/8snOHMn 9RpG6DxmoaYM4Vxpa3iYaCHoUuMsEE7p2xQWcILdwmd2YZUnJ4eA0OCWneA8Qy8ruL ST7jwRmPY7dcQ== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH 6.18.y 5/5] mm/damon/core: filter out damos address filter-split failed region Date: Sat, 7 Nov 2026 12:10:01 -0800 Message-ID: <20261107201001.206120-6-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261107201001.206120-1-sj@kernel.org> References: <20261107201001.206120-1-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 | 16 ++++++++++++---- mm/damon/tests/core-kunit.h | 16 +++++++++++----- 2 files changed, 23 insertions(+), 9 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 00cd0e2a1e341..dc8608c3cae40 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1812,13 +1812,14 @@ static void damos_update_stat(struct damos *s, static bool damos_filter_match(struct damon_ctx *ctx, struct damon_target *t, struct damon_region *r, struct damos_filter *filter, - unsigned long min_sz_region) + unsigned long min_sz_region, 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) { @@ -1844,12 +1845,13 @@ static bool damos_filter_match(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: @@ -1863,10 +1865,16 @@ 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; s->core_filters_allowed = false; damos_for_each_filter(filter, s) { - if (damos_filter_match(ctx, t, r, filter, ctx->min_sz_region)) { + matching = damos_filter_match(ctx, t, r, filter, + ctx->min_sz_region, &err); + if (err) + return true; + if (matching) { if (filter->allow) s->core_filters_allowed = true; return !filter->allow; diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h index 0ce6481319432..814197da4f507 100644 --- a/mm/damon/tests/core-kunit.h +++ b/mm/damon/tests/core-kunit.h @@ -548,6 +548,7 @@ 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, false); if (!f) @@ -570,28 +571,32 @@ static void damos_test_filter_out(struct kunit *test) /* region in the range */ KUNIT_EXPECT_TRUE(test, - damos_filter_match(NULL, t, r, f, DAMON_MIN_REGION)); + damos_filter_match(NULL, t, r, f, DAMON_MIN_REGION, + &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_match(NULL, t, r, f, DAMON_MIN_REGION)); + damos_filter_match(NULL, t, r, f, DAMON_MIN_REGION, + &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_match(NULL, t, r, f, DAMON_MIN_REGION)); + damos_filter_match(NULL, t, r, f, DAMON_MIN_REGION, + &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_match(NULL, t, r, f, DAMON_MIN_REGION)); + damos_filter_match(NULL, t, r, f, DAMON_MIN_REGION, + &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); @@ -607,7 +612,8 @@ static void damos_test_filter_out(struct kunit *test) r->ar.start = DAMON_MIN_REGION * 2; r->ar.end = DAMON_MIN_REGION * 8; KUNIT_EXPECT_TRUE(test, - damos_filter_match(NULL, t, r, f, DAMON_MIN_REGION)); + damos_filter_match(NULL, t, r, f, DAMON_MIN_REGION, + &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