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=1794046483; b=Xr/iTjYi4P6bZZfKWmjwgih9AyCj5ZxItockwvZzdX3NRTnduHgMseAZKFGz0Zew0rBJ d87G01l5HA7glyR8iWyef8QM5o3UHTF8pvUCLee8+WTsVgBGkQtM0BfklgqqycybHCRwO WjG/n1LZrdZlZWxh2yUXUSyYOSe2v8+cPnOfPB5KaZQLwe26mk3srobsM9NQhyXFHTUwm F2ziu/bk5nDiABmYZzv21CcWEX6v00V3fq1nIbiOOlKsRzg1GrzXxtDC5LyBJy3FBSswn qu8kTauzSqi0Vi7HMRpEJWQVDh1C6OiUwwPQ4C8/2GhOQnpzSn3GmMi6p6Gob66sfDA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794046483; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=hiK9yWjwPbF9TdJG/p5Ev9P/FhYe1GfcIp9gIfSeC9g=; b=bBXp98rEuXGV/x8Y/qjBOGhxGTIdTi0YQjcWLTyrVdOt10BHZ5LXbd0hdU55z1E8wQr5 Spqtf7zyrR1H53F9OVLZU1LHE3FUb9Ese90iLdu6iXZxA9GJiqyy2Qc+MAmOlisqogoPa 79FGSiNgRxtuxo4Fgnz4csFddPwmt7OjbLfgEZ/6oJeokNdxAVf8gdfpEt5E+gCWrO5ps T8ckCIiFYT3oEJhM8yDHuebdiexGOLVs6ZbeBqpr4LZihQ5MFcayafqSSh1+H3M8IjjoN 6BweYBtoPiYc7u02KKWpwu3v4QBS5EdAPnMLZxKnMHHwGyA/5LGsHxoWKDbej6H8I+A== 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=NRwtKLVa; 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 EB4A7606A32C for ; Sat, 7 Nov 2026 10:14:42 +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=NRwtKLVa Received: by smtp.kernel.org (Postfix) with ESMTPSA id 254E71F0089F; Sat, 7 Nov 2026 10:14:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794046482; bh=hiK9yWjwPbF9TdJG/p5Ev9P/FhYe1GfcIp9gIfSeC9g=; h=From:To:Cc:Subject:Date; b=NRwtKLVaNLVS2z0Tmu+5oqL/WIlYs5qPGx0J4AvKeh+99Od6bpPUA1U0VBwqZhOQh QAsiZm8F/+Da9mtTFYE+b57m3YFhGcDre4kIxDvXOEXyu4oRjWCki7MMhDGhaAGbsK gCEDu0jkeb/QgjlY4HqiQRdyXSx9RRK6fKzB6GZ7LqD9BxYg9x7gfAAbxmJYWDYaD8 B1RccvBSEmpeI0PrXoYvmDgZGVH2HkS3xOfDNFZ35f+pikmBkDM3F5IgMK3S1GaiiP tRauajbHTAGTzc/Vd8BkYf9SlEkFYe1IV92nH9U1y+BMnuOVApIaPipgTzElBO7MoE O9A15i7rdi1Qg== From: Sasha Levin To: sj@kernel.org, akpm@linux-foundation.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/damon/core: filter out damos address filter-split failed region" failed to apply to 6.18-stable tree Date: Sat, 7 Nov 2026 05:14:41 -0500 Message-ID: <20261107051441-failed-6.18-bbeec2d8324d@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x bbeec2d8324d7aac438bb12dd2d22b184e0a8d43 # git commit -s git send-email --to '' --in-reply-to '20261107051441-failed-6.18-bbeec2d8324d@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From bbeec2d8324d7aac438bb12dd2d22b184e0a8d43 Mon Sep 17 00:00:00 2001 From: SJ Park Date: Mon, 19 Oct 2026 17:41:18 -0700 Subject: [PATCH] mm/damon/core: filter out damos address filter-split failed region 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 --- mm/damon/core.c | 16 ++++++++++++---- mm/damon/tests/core-kunit.h | 11 ++++++----- 2 files changed, 18 insertions(+), 9 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index b63e60ef89901..479169dc9ac75 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2551,13 +2551,14 @@ 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_region_sz) + unsigned long min_region_sz, int *err) { bool matched = false; struct damon_target *ti; int target_idx = 0; unsigned long start, end, wsum; + *err = 0; switch (filter->type) { case DAMOS_FILTER_TYPE_TARGET: damon_for_each_target(ti, ctx) { @@ -2583,12 +2584,13 @@ 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; case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM: @@ -2607,10 +2609,16 @@ static bool damos_core_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_core_filter(filter, s) { - if (damos_filter_match(ctx, t, r, filter, ctx->min_region_sz)) { + matching = damos_filter_match(ctx, t, r, filter, + ctx->min_region_sz, &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 3fbb4e4e36fac..43e2f950f8ff4 100644 --- a/mm/damon/tests/core-kunit.h +++ b/mm/damon/tests/core-kunit.h @@ -1783,6 +1783,7 @@ 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) @@ -1803,27 +1804,27 @@ static void damos_test_filter_out(struct kunit *test) damon_add_region(r, t); /* region in the range */ - KUNIT_EXPECT_TRUE(test, damos_filter_match(NULL, t, r, f, 1)); + KUNIT_EXPECT_TRUE(test, damos_filter_match(NULL, t, r, f, 1, &err)); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); /* region before the range */ r->ar.start = 1; r->ar.end = 2; KUNIT_EXPECT_FALSE(test, - damos_filter_match(NULL, t, r, f, 1)); + damos_filter_match(NULL, t, r, f, 1, &err)); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); /* region after the range */ r->ar.start = 6; r->ar.end = 8; KUNIT_EXPECT_FALSE(test, - damos_filter_match(NULL, t, r, f, 1)); + damos_filter_match(NULL, t, r, f, 1, &err)); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); /* region started before the range */ r->ar.start = 1; r->ar.end = 4; - KUNIT_EXPECT_FALSE(test, damos_filter_match(NULL, t, r, f, 1)); + KUNIT_EXPECT_FALSE(test, damos_filter_match(NULL, t, r, f, 1, &err)); /* filter should have split the region */ KUNIT_EXPECT_EQ(test, r->ar.start, 1); KUNIT_EXPECT_EQ(test, r->ar.end, 2); @@ -1839,7 +1840,7 @@ static void damos_test_filter_out(struct kunit *test) r->ar.start = 2; r->ar.end = 8; KUNIT_EXPECT_TRUE(test, - damos_filter_match(NULL, t, r, f, 1)); + damos_filter_match(NULL, t, r, f, 1, &err)); /* filter should have split the region */ KUNIT_EXPECT_EQ(test, r->ar.start, 2); KUNIT_EXPECT_EQ(test, r->ar.end, 6); -- 2.53.0