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=1794047949; b=PRQyzIIXjGF869CpIvSQ+10lwX+OLtJMoByE4tfPIv7989VpTs2RdBKN3dZUTmn3QIUl kdfv2gVPCSgy9LJTAFR8+7YwIACVCcnw+BCoD3zC0gWA+P6ssTNok4O1TcWNFlOmKN7LX ETJPRBZ02Tbcpdf6RlpyzPbukqOtHu5xIp0ccuCFh7rsaic43D/fyIlEuIsBDSycw4U2U JVxn8Bbg+cgD6VCZ/nl97dgyGolKm3MZZlB+SPUPe5J9gDvrDaB/I+DwcivXhx+JmscgE RV3IC+WJ+QM19iwoCIhLtJvHycSGYrhYl5o8HUGXcICmb7rLzbAzFL7wgNpJW/CMihw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047949; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=1AJPqVrs/yPAk4gmZrxbXi320w54XwLe/KhK4TX6Mfs=; b=ZQPqBRDuXRPx1yitHXB3QI0Llj+a7PZEbjqP6245hrt6du3/U/pGgVAkFb3Lk1pI3qLF QkWKF592q0+pDwH5BOieoW1ZwdxujEXhSWzgeMwZU9kErtgiP27vmsTCXzMfdBR+dwo6f fDwZGRaMiuOhiEewSfAFSqjUpgzUo75N0pptKfDJvO0tgjRlx3SrFtBQJ/wS+IhGMhY29 1TeHQcR2ewB7bLNjBcbxiD8XjQo+J36jSmfyjbHPvG/aN4FEjG+LYCHoQlaTfINbn8UOO flBLj7eZJEHJk//yzFExjNbB6LSzMkIbJHlJxrurcbOgUp8tafDpeRUFJ8yioJ1+ZqQ== 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=oAbN4QqE; 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 76F78606A32C for ; Sat, 7 Nov 2026 10:39:09 +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=oAbN4QqE Received: by smtp.kernel.org (Postfix) with ESMTPSA id E56441F0089F; Sat, 7 Nov 2026 10:39:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047949; bh=1AJPqVrs/yPAk4gmZrxbXi320w54XwLe/KhK4TX6Mfs=; h=From:To:Cc:Subject:Date; b=oAbN4QqEFxSgY862RYWCEAEegCbkelsnizi3HEDzm5kMy6DZJjIXDMcOGn9BGMM6X hZNL+CJXxolYLQVuU3KEPoagxaJWLK7DwHTrYTrdQ/xKh2lMr7xrEKfdA7gdP+MGzy BqHDEKyZ1XE3g3JV+7GgcnDiigOQz2U5+KBXdN+R4pqB8no6l/aS6lz2yRtdum1dmW rYbvZo8acLtzCuawKY/Kwd9q/kykGZ7ZnjkcYDlpmPNh86LXgijVtreunzJnNnKG7K CexbRgWlCo5nMhReE2T1AvApG6WsL1QeJXO7kfnSJH9W07D+kH5iUlajmro2f2pYub LHy9Ss8F1/uKQ== 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 6.6-stable tree Date: Sat, 7 Nov 2026 05:39:07 -0500 Message-ID: <20261107053907-failed-6.6-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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x bbeec2d8324d7aac438bb12dd2d22b184e0a8d43 # git commit -s git send-email --to '' --in-reply-to '20261107053907-failed-6.6-bbeec2d8324d@kernel.org' --subject-prefix 'PATCH 6.6.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