[PATCH 5.15.y 1/2] skmsg: convert struct sk_msg_sg::copy to a bitmap

[PATCH 5.15.y 1/2] skmsg: convert struct sk_msg_sg::copy to a bitmap

[Sasha Levin]

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 5a8fb33e530512ee67a11b30f3451a4f030f4b01 ]

We have plans for increasing MAX_SKB_FRAGS, but sk_msg_sg::copy
is currently an unsigned long, limiting MAX_SKB_FRAGS to 30 on 32bit arches.

Convert it to a bitmap, as Jakub suggested.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 406e8a651a7b ("net: skmsg: preserve sg.copy across SG transforms")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/skmsg.h | 11 +++++------
 net/core/filter.c     |  4 ++--
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 5d3e4d4d9438e2..7bc66fd7fc58c1 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -29,7 +29,7 @@ struct sk_msg_sg {
 	u32				end;
 	u32				size;
 	u32				copybreak;
-	unsigned long			copy;
+	DECLARE_BITMAP(copy, MAX_MSG_FRAGS + 2);
 	/* The extra two elements:
 	 * 1) used for chaining the front and sections when the list becomes
 	 *    partitioned (e.g. end < start). The crypto APIs require the
@@ -38,7 +38,6 @@ struct sk_msg_sg {
 	 */
 	struct scatterlist		data[MAX_MSG_FRAGS + 2];
 };
-static_assert(BITS_PER_LONG >= NR_MSG_FRAG_IDS);
 
 /* UAPI in filter.c depends on struct sk_msg_sg being first element. */
 struct sk_msg {
@@ -236,7 +235,7 @@ static inline void sk_msg_compute_data_pointers(struct sk_msg *msg)
 {
 	struct scatterlist *sge = sk_msg_elem(msg, msg->sg.start);
 
-	if (test_bit(msg->sg.start, &msg->sg.copy)) {
+	if (test_bit(msg->sg.start, msg->sg.copy)) {
 		msg->data = NULL;
 		msg->data_end = NULL;
 	} else {
@@ -255,7 +254,7 @@ static inline void sk_msg_page_add(struct sk_msg *msg, struct page *page,
 	sg_set_page(sge, page, len, offset);
 	sg_unmark_end(sge);
 
-	__set_bit(msg->sg.end, &msg->sg.copy);
+	__set_bit(msg->sg.end, msg->sg.copy);
 	msg->sg.size += len;
 	sk_msg_iter_next(msg, end);
 }
@@ -264,9 +263,9 @@ static inline void sk_msg_sg_copy(struct sk_msg *msg, u32 i, bool copy_state)
 {
 	do {
 		if (copy_state)
-			__set_bit(i, &msg->sg.copy);
+			__set_bit(i, msg->sg.copy);
 		else
-			__clear_bit(i, &msg->sg.copy);
+			__clear_bit(i, msg->sg.copy);
 		sk_msg_iter_var_next(i);
 		if (i == msg->sg.end)
 			break;
diff --git a/net/core/filter.c b/net/core/filter.c
index 6a1210abe4625e..5874ecb192098c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2660,7 +2660,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	 * account for the headroom.
 	 */
 	bytes_sg_total = start - offset + bytes;
-	if (!test_bit(i, &msg->sg.copy) && bytes_sg_total <= len)
+	if (!test_bit(i, msg->sg.copy) && bytes_sg_total <= len)
 		goto out;
 
 	/* At this point we need to linearize multiple scatterlist
@@ -2883,7 +2883,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Place newly allocated data buffer */
 	sk_mem_charge(msg->sk, len);
 	msg->sg.size += len;
-	__clear_bit(new, &msg->sg.copy);
+	__clear_bit(new, msg->sg.copy);
 	sg_set_page(&msg->sg.data[new], page, len + copy, 0);
 	if (rsge.length) {
 		get_page(sg_page(&rsge));
-- 
2.53.0

FAILED: patch "[PATCH] bpf, sockmap: keep sk_msg copy state in sync" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-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 <stable@vger.kernel.org>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 2ccbc9a3874620c9623419034f572e4507c33e4f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026071404-skirmish-glider-a33e@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2ccbc9a3874620c9623419034f572e4507c33e4f Mon Sep 17 00:00:00 2001
From: Zhang Cen <rollkingzzc@gmail.com>
Date: Mon, 15 Jun 2026 10:19:56 +0800
Subject: [PATCH] bpf, sockmap: keep sk_msg copy state in sync

SK_MSG uses msg->sg.copy as per-scatterlist-entry provenance. Entries
with this bit set are copied before data/data_end are exposed to SK_MSG
BPF programs for direct packet access.

bpf_msg_pull_data(), bpf_msg_push_data(), and bpf_msg_pop_data()
rewrite the sk_msg scatterlist ring by collapsing, splitting, and
shifting entries. These operations move msg->sg.data[] entries, but the
parallel copy bitmap can be left behind on the old slot. A copied entry
can then return to msg->sg.start with its copy bit clear and be exposed
as directly writable packet data.

This corruption path requires an attached SK_MSG BPF program that calls
the mutating helpers; ordinary sockmap/TLS traffic that never runs
push/pop/pull helper sequences is not affected.

Keep msg->sg.copy synchronized with scatterlist entry moves, preserve
the copy bit when an entry is split, clear it when a helper replaces an
entry with a private page, and clear slots vacated by pull-data
compaction.

Fixes: 015632bb30da ("bpf: sk_msg program helper bpf_sk_msg_pull_data")
Fixes: 6fff607e2f14 ("bpf: sk_msg program helper bpf_msg_push_data")
Fixes: 7246d8ed4dcc ("bpf: helper to pop data from messages")
Cc: stable@vger.kernel.org
Co-developed-by: Han Guidong <2045gemini@gmail.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Han Guidong <2045gemini@gmail.com>
Signed-off-by: Zhang Cen <rollkingzzc@gmail.com>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://lore.kernel.org/r/20260615021959.140010-4-jiayuan.chen@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/net/core/filter.c b/net/core/filter.c
index 978e740792be..3ecac0eb7da1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2654,6 +2654,38 @@ static void sk_msg_reset_curr(struct sk_msg *msg)
 	}
 }
 
+static bool sk_msg_elem_is_copy(const struct sk_msg *msg, u32 i)
+{
+	return test_bit(i, msg->sg.copy);
+}
+
+static void sk_msg_clear_elem_copy(struct sk_msg *msg, u32 i)
+{
+	__clear_bit(i, msg->sg.copy);
+}
+
+static void sk_msg_set_elem_copy(struct sk_msg *msg, u32 i)
+{
+	__set_bit(i, msg->sg.copy);
+}
+
+static void sk_msg_clear_copy_range(struct sk_msg *msg, u32 start, u32 end)
+{
+	while (start != end) {
+		sk_msg_clear_elem_copy(msg, start);
+		sk_msg_iter_var_next(start);
+	}
+}
+
+static void sk_msg_sg_move(struct sk_msg *msg, u32 dst, u32 src)
+{
+	msg->sg.data[dst] = msg->sg.data[src];
+	if (sk_msg_elem_is_copy(msg, src))
+		sk_msg_set_elem_copy(msg, dst);
+	else
+		sk_msg_clear_elem_copy(msg, dst);
+}
+
 static const struct bpf_func_proto bpf_msg_cork_bytes_proto = {
 	.func           = bpf_msg_cork_bytes,
 	.gpl_only       = false,
@@ -2692,7 +2724,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	 * account for the headroom.
 	 */
 	bytes_sg_total = start - offset + bytes;
-	if (!test_bit(i, msg->sg.copy) && bytes_sg_total <= len)
+	if (!sk_msg_elem_is_copy(msg, i) && bytes_sg_total <= len)
 		goto out;
 
 	/* At this point we need to linearize multiple scatterlist
@@ -2738,6 +2770,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	} while (i != last_sge);
 
 	sg_set_page(&msg->sg.data[first_sge], page, copy, 0);
+	sk_msg_clear_elem_copy(msg, first_sge);
 
 	/* To repair sg ring we need to shift entries. If we only
 	 * had a single entry though we can just replace it and
@@ -2747,8 +2780,14 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	shift = last_sge > first_sge ?
 		last_sge - first_sge - 1 :
 		NR_MSG_FRAG_IDS - first_sge + last_sge - 1;
-	if (!shift)
+	if (!shift) {
+		sk_msg_clear_elem_copy(msg, msg->sg.end);
 		goto out;
+	}
+
+	i = first_sge;
+	sk_msg_iter_var_next(i);
+	sk_msg_clear_copy_range(msg, i, last_sge);
 
 	i = first_sge;
 	sk_msg_iter_var_next(i);
@@ -2762,16 +2801,18 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 		if (move_from == msg->sg.end)
 			break;
 
-		msg->sg.data[i] = msg->sg.data[move_from];
+		sk_msg_sg_move(msg, i, move_from);
 		msg->sg.data[move_from].length = 0;
 		msg->sg.data[move_from].page_link = 0;
 		msg->sg.data[move_from].offset = 0;
+		sk_msg_clear_elem_copy(msg, move_from);
 		sk_msg_iter_var_next(i);
 	} while (1);
 
 	msg->sg.end = msg->sg.end - shift > msg->sg.end ?
 		      msg->sg.end - shift + NR_MSG_FRAG_IDS :
 		      msg->sg.end - shift;
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 out:
 	sk_msg_reset_curr(msg);
 	msg->data = sg_virt(&msg->sg.data[first_sge]) + start - offset;
@@ -2792,8 +2833,10 @@ static const struct bpf_func_proto bpf_msg_pull_data_proto = {
 BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	   u32, len, u64, flags)
 {
+	bool sge_copy = false, nsge_copy = false, nnsge_copy = false;
 	struct scatterlist sge, nsge, nnsge, rsge = {0}, *psge;
 	u32 new, i = 0, l = 0, space, copy = 0, offset = 0;
+	bool rsge_copy = false;
 	u8 *raw, *to, *from;
 	struct page *page;
 
@@ -2869,6 +2912,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 			sk_msg_iter_var_prev(i);
 		psge = sk_msg_elem(msg, i);
 		rsge = sk_msg_elem_cpy(msg, i);
+		rsge_copy = sk_msg_elem_is_copy(msg, i);
 
 		psge->length = start - offset;
 		rsge.length -= psge->length;
@@ -2894,23 +2938,34 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Shift one or two slots as needed */
 	sge = sk_msg_elem_cpy(msg, new);
 	sg_unmark_end(&sge);
+	sge_copy = sk_msg_elem_is_copy(msg, new);
 
 	nsge = sk_msg_elem_cpy(msg, i);
+	nsge_copy = sk_msg_elem_is_copy(msg, i);
 	if (rsge.length) {
 		sk_msg_iter_var_next(i);
 		nnsge = sk_msg_elem_cpy(msg, i);
+		nnsge_copy = sk_msg_elem_is_copy(msg, i);
 		sk_msg_iter_next(msg, end);
 	}
 
 	while (i != msg->sg.end) {
 		msg->sg.data[i] = sge;
+		if (sge_copy)
+			sk_msg_set_elem_copy(msg, i);
+		else
+			sk_msg_clear_elem_copy(msg, i);
 		sge = nsge;
+		sge_copy = nsge_copy;
 		sk_msg_iter_var_next(i);
 		if (rsge.length) {
 			nsge = nnsge;
+			nsge_copy = nnsge_copy;
 			nnsge = sk_msg_elem_cpy(msg, i);
+			nnsge_copy = sk_msg_elem_is_copy(msg, i);
 		} else {
 			nsge = sk_msg_elem_cpy(msg, i);
+			nsge_copy = sk_msg_elem_is_copy(msg, i);
 		}
 	}
 
@@ -2918,13 +2973,18 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Place newly allocated data buffer */
 	sk_mem_charge(msg->sk, len);
 	msg->sg.size += len;
-	__clear_bit(new, msg->sg.copy);
+	sk_msg_clear_elem_copy(msg, new);
 	sg_set_page(&msg->sg.data[new], page, len + copy, 0);
 	if (rsge.length) {
 		get_page(sg_page(&rsge));
 		sk_msg_iter_var_next(new);
 		msg->sg.data[new] = rsge;
+		if (rsge_copy)
+			sk_msg_set_elem_copy(msg, new);
+		else
+			sk_msg_clear_elem_copy(msg, new);
 	}
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 
 	sk_msg_reset_curr(msg);
 	sk_msg_compute_data_pointers(msg);
@@ -2950,27 +3010,38 @@ static void sk_msg_shift_left(struct sk_msg *msg, int i)
 	do {
 		prev = i;
 		sk_msg_iter_var_next(i);
-		msg->sg.data[prev] = msg->sg.data[i];
+		sk_msg_sg_move(msg, prev, i);
 	} while (i != msg->sg.end);
 
 	sk_msg_iter_prev(msg, end);
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 }
 
 static void sk_msg_shift_right(struct sk_msg *msg, int i)
 {
 	struct scatterlist tmp, sge;
+	bool tmp_copy, sge_copy;
 
 	sk_msg_iter_next(msg, end);
 	sge = sk_msg_elem_cpy(msg, i);
+	sge_copy = sk_msg_elem_is_copy(msg, i);
 	sk_msg_iter_var_next(i);
 	tmp = sk_msg_elem_cpy(msg, i);
+	tmp_copy = sk_msg_elem_is_copy(msg, i);
 
 	while (i != msg->sg.end) {
 		msg->sg.data[i] = sge;
+		if (sge_copy)
+			sk_msg_set_elem_copy(msg, i);
+		else
+			sk_msg_clear_elem_copy(msg, i);
 		sk_msg_iter_var_next(i);
 		sge = tmp;
+		sge_copy = tmp_copy;
 		tmp = sk_msg_elem_cpy(msg, i);
+		tmp_copy = sk_msg_elem_is_copy(msg, i);
 	}
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 }
 
 BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
@@ -3027,8 +3098,10 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
 	 */
 	if (start != offset) {
 		struct scatterlist *nsge, *sge = sk_msg_elem(msg, i);
+		bool sge_copy = sk_msg_elem_is_copy(msg, i);
 		int a = start - offset;
 		int b = sge->length - pop - a;
+		u32 sge_idx = i;
 
 		sk_msg_iter_var_next(i);
 
@@ -3041,6 +3114,10 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
 				sg_set_page(nsge,
 					    sg_page(sge),
 					    b, sge->offset + pop + a);
+				if (sge_copy)
+					sk_msg_set_elem_copy(msg, i);
+				else
+					sk_msg_clear_elem_copy(msg, i);
 			} else {
 				struct page *page, *orig;
 				u8 *to, *from;
@@ -3057,6 +3134,7 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
 				memcpy(to, from, a);
 				memcpy(to + a, from + a + pop, b);
 				sg_set_page(sge, page, a + b, 0);
+				sk_msg_clear_elem_copy(msg, sge_idx);
 				put_page(orig);
 			}
 			pop = 0;

[PATCH 5.15.y 1/2] skmsg: convert struct sk_msg_sg::copy to a bitmap

[Sasha Levin]

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 5a8fb33e530512ee67a11b30f3451a4f030f4b01 ]

We have plans for increasing MAX_SKB_FRAGS, but sk_msg_sg::copy
is currently an unsigned long, limiting MAX_SKB_FRAGS to 30 on 32bit arches.

Convert it to a bitmap, as Jakub suggested.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 2ccbc9a38746 ("bpf, sockmap: keep sk_msg copy state in sync")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/skmsg.h | 11 +++++------
 net/core/filter.c     |  4 ++--
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 5d3e4d4d9438e2..7bc66fd7fc58c1 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -29,7 +29,7 @@ struct sk_msg_sg {
 	u32				end;
 	u32				size;
 	u32				copybreak;
-	unsigned long			copy;
+	DECLARE_BITMAP(copy, MAX_MSG_FRAGS + 2);
 	/* The extra two elements:
 	 * 1) used for chaining the front and sections when the list becomes
 	 *    partitioned (e.g. end < start). The crypto APIs require the
@@ -38,7 +38,6 @@ struct sk_msg_sg {
 	 */
 	struct scatterlist		data[MAX_MSG_FRAGS + 2];
 };
-static_assert(BITS_PER_LONG >= NR_MSG_FRAG_IDS);
 
 /* UAPI in filter.c depends on struct sk_msg_sg being first element. */
 struct sk_msg {
@@ -236,7 +235,7 @@ static inline void sk_msg_compute_data_pointers(struct sk_msg *msg)
 {
 	struct scatterlist *sge = sk_msg_elem(msg, msg->sg.start);
 
-	if (test_bit(msg->sg.start, &msg->sg.copy)) {
+	if (test_bit(msg->sg.start, msg->sg.copy)) {
 		msg->data = NULL;
 		msg->data_end = NULL;
 	} else {
@@ -255,7 +254,7 @@ static inline void sk_msg_page_add(struct sk_msg *msg, struct page *page,
 	sg_set_page(sge, page, len, offset);
 	sg_unmark_end(sge);
 
-	__set_bit(msg->sg.end, &msg->sg.copy);
+	__set_bit(msg->sg.end, msg->sg.copy);
 	msg->sg.size += len;
 	sk_msg_iter_next(msg, end);
 }
@@ -264,9 +263,9 @@ static inline void sk_msg_sg_copy(struct sk_msg *msg, u32 i, bool copy_state)
 {
 	do {
 		if (copy_state)
-			__set_bit(i, &msg->sg.copy);
+			__set_bit(i, msg->sg.copy);
 		else
-			__clear_bit(i, &msg->sg.copy);
+			__clear_bit(i, msg->sg.copy);
 		sk_msg_iter_var_next(i);
 		if (i == msg->sg.end)
 			break;
diff --git a/net/core/filter.c b/net/core/filter.c
index 6a1210abe4625e..5874ecb192098c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2660,7 +2660,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	 * account for the headroom.
 	 */
 	bytes_sg_total = start - offset + bytes;
-	if (!test_bit(i, &msg->sg.copy) && bytes_sg_total <= len)
+	if (!test_bit(i, msg->sg.copy) && bytes_sg_total <= len)
 		goto out;
 
 	/* At this point we need to linearize multiple scatterlist
@@ -2883,7 +2883,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Place newly allocated data buffer */
 	sk_mem_charge(msg->sk, len);
 	msg->sg.size += len;
-	__clear_bit(new, &msg->sg.copy);
+	__clear_bit(new, msg->sg.copy);
 	sg_set_page(&msg->sg.data[new], page, len + copy, 0);
 	if (rsge.length) {
 		get_page(sg_page(&rsge));
-- 
2.53.0

[PATCH 5.15.y 2/2] bpf, sockmap: keep sk_msg copy state in sync

[Sasha Levin]

From: Zhang Cen <rollkingzzc@gmail.com>

[ Upstream commit 2ccbc9a3874620c9623419034f572e4507c33e4f ]

SK_MSG uses msg->sg.copy as per-scatterlist-entry provenance. Entries
with this bit set are copied before data/data_end are exposed to SK_MSG
BPF programs for direct packet access.

bpf_msg_pull_data(), bpf_msg_push_data(), and bpf_msg_pop_data()
rewrite the sk_msg scatterlist ring by collapsing, splitting, and
shifting entries. These operations move msg->sg.data[] entries, but the
parallel copy bitmap can be left behind on the old slot. A copied entry
can then return to msg->sg.start with its copy bit clear and be exposed
as directly writable packet data.

This corruption path requires an attached SK_MSG BPF program that calls
the mutating helpers; ordinary sockmap/TLS traffic that never runs
push/pop/pull helper sequences is not affected.

Keep msg->sg.copy synchronized with scatterlist entry moves, preserve
the copy bit when an entry is split, clear it when a helper replaces an
entry with a private page, and clear slots vacated by pull-data
compaction.

Fixes: 015632bb30da ("bpf: sk_msg program helper bpf_sk_msg_pull_data")
Fixes: 6fff607e2f14 ("bpf: sk_msg program helper bpf_msg_push_data")
Fixes: 7246d8ed4dcc ("bpf: helper to pop data from messages")
Cc: stable@vger.kernel.org
Co-developed-by: Han Guidong <2045gemini@gmail.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Han Guidong <2045gemini@gmail.com>
Signed-off-by: Zhang Cen <rollkingzzc@gmail.com>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://lore.kernel.org/r/20260615021959.140010-4-jiayuan.chen@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/filter.c | 88 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 83 insertions(+), 5 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 5874ecb192098c..8f2ddec10be0f3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2622,6 +2622,38 @@ static void sk_msg_reset_curr(struct sk_msg *msg)
 	}
 }
 
+static bool sk_msg_elem_is_copy(const struct sk_msg *msg, u32 i)
+{
+	return test_bit(i, msg->sg.copy);
+}
+
+static void sk_msg_clear_elem_copy(struct sk_msg *msg, u32 i)
+{
+	__clear_bit(i, msg->sg.copy);
+}
+
+static void sk_msg_set_elem_copy(struct sk_msg *msg, u32 i)
+{
+	__set_bit(i, msg->sg.copy);
+}
+
+static void sk_msg_clear_copy_range(struct sk_msg *msg, u32 start, u32 end)
+{
+	while (start != end) {
+		sk_msg_clear_elem_copy(msg, start);
+		sk_msg_iter_var_next(start);
+	}
+}
+
+static void sk_msg_sg_move(struct sk_msg *msg, u32 dst, u32 src)
+{
+	msg->sg.data[dst] = msg->sg.data[src];
+	if (sk_msg_elem_is_copy(msg, src))
+		sk_msg_set_elem_copy(msg, dst);
+	else
+		sk_msg_clear_elem_copy(msg, dst);
+}
+
 static const struct bpf_func_proto bpf_msg_cork_bytes_proto = {
 	.func           = bpf_msg_cork_bytes,
 	.gpl_only       = false,
@@ -2660,7 +2692,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	 * account for the headroom.
 	 */
 	bytes_sg_total = start - offset + bytes;
-	if (!test_bit(i, msg->sg.copy) && bytes_sg_total <= len)
+	if (!sk_msg_elem_is_copy(msg, i) && bytes_sg_total <= len)
 		goto out;
 
 	/* At this point we need to linearize multiple scatterlist
@@ -2706,6 +2738,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	} while (i != last_sge);
 
 	sg_set_page(&msg->sg.data[first_sge], page, copy, 0);
+	sk_msg_clear_elem_copy(msg, first_sge);
 
 	/* To repair sg ring we need to shift entries. If we only
 	 * had a single entry though we can just replace it and
@@ -2715,8 +2748,14 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	shift = last_sge > first_sge ?
 		last_sge - first_sge - 1 :
 		NR_MSG_FRAG_IDS - first_sge + last_sge - 1;
-	if (!shift)
+	if (!shift) {
+		sk_msg_clear_elem_copy(msg, msg->sg.end);
 		goto out;
+	}
+
+	i = first_sge;
+	sk_msg_iter_var_next(i);
+	sk_msg_clear_copy_range(msg, i, last_sge);
 
 	i = first_sge;
 	sk_msg_iter_var_next(i);
@@ -2730,16 +2769,18 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 		if (move_from == msg->sg.end)
 			break;
 
-		msg->sg.data[i] = msg->sg.data[move_from];
+		sk_msg_sg_move(msg, i, move_from);
 		msg->sg.data[move_from].length = 0;
 		msg->sg.data[move_from].page_link = 0;
 		msg->sg.data[move_from].offset = 0;
+		sk_msg_clear_elem_copy(msg, move_from);
 		sk_msg_iter_var_next(i);
 	} while (1);
 
 	msg->sg.end = msg->sg.end - shift > msg->sg.end ?
 		      msg->sg.end - shift + NR_MSG_FRAG_IDS :
 		      msg->sg.end - shift;
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 out:
 	sk_msg_reset_curr(msg);
 	msg->data = sg_virt(&msg->sg.data[first_sge]) + start - offset;
@@ -2760,8 +2801,10 @@ static const struct bpf_func_proto bpf_msg_pull_data_proto = {
 BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	   u32, len, u64, flags)
 {
+	bool sge_copy = false, nsge_copy = false, nnsge_copy = false;
 	struct scatterlist sge, nsge, nnsge, rsge = {0}, *psge;
 	u32 new, i = 0, l = 0, space, copy = 0, offset = 0;
+	bool rsge_copy = false;
 	u8 *raw, *to, *from;
 	struct page *page;
 
@@ -2834,6 +2877,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 			sk_msg_iter_var_prev(i);
 		psge = sk_msg_elem(msg, i);
 		rsge = sk_msg_elem_cpy(msg, i);
+		rsge_copy = sk_msg_elem_is_copy(msg, i);
 
 		psge->length = start - offset;
 		rsge.length -= psge->length;
@@ -2859,23 +2903,34 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Shift one or two slots as needed */
 	sge = sk_msg_elem_cpy(msg, new);
 	sg_unmark_end(&sge);
+	sge_copy = sk_msg_elem_is_copy(msg, new);
 
 	nsge = sk_msg_elem_cpy(msg, i);
+	nsge_copy = sk_msg_elem_is_copy(msg, i);
 	if (rsge.length) {
 		sk_msg_iter_var_next(i);
 		nnsge = sk_msg_elem_cpy(msg, i);
+		nnsge_copy = sk_msg_elem_is_copy(msg, i);
 		sk_msg_iter_next(msg, end);
 	}
 
 	while (i != msg->sg.end) {
 		msg->sg.data[i] = sge;
+		if (sge_copy)
+			sk_msg_set_elem_copy(msg, i);
+		else
+			sk_msg_clear_elem_copy(msg, i);
 		sge = nsge;
+		sge_copy = nsge_copy;
 		sk_msg_iter_var_next(i);
 		if (rsge.length) {
 			nsge = nnsge;
+			nsge_copy = nnsge_copy;
 			nnsge = sk_msg_elem_cpy(msg, i);
+			nnsge_copy = sk_msg_elem_is_copy(msg, i);
 		} else {
 			nsge = sk_msg_elem_cpy(msg, i);
+			nsge_copy = sk_msg_elem_is_copy(msg, i);
 		}
 	}
 
@@ -2883,13 +2938,18 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Place newly allocated data buffer */
 	sk_mem_charge(msg->sk, len);
 	msg->sg.size += len;
-	__clear_bit(new, msg->sg.copy);
+	sk_msg_clear_elem_copy(msg, new);
 	sg_set_page(&msg->sg.data[new], page, len + copy, 0);
 	if (rsge.length) {
 		get_page(sg_page(&rsge));
 		sk_msg_iter_var_next(new);
 		msg->sg.data[new] = rsge;
+		if (rsge_copy)
+			sk_msg_set_elem_copy(msg, new);
+		else
+			sk_msg_clear_elem_copy(msg, new);
 	}
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 
 	sk_msg_reset_curr(msg);
 	sk_msg_compute_data_pointers(msg);
@@ -2915,27 +2975,38 @@ static void sk_msg_shift_left(struct sk_msg *msg, int i)
 	do {
 		prev = i;
 		sk_msg_iter_var_next(i);
-		msg->sg.data[prev] = msg->sg.data[i];
+		sk_msg_sg_move(msg, prev, i);
 	} while (i != msg->sg.end);
 
 	sk_msg_iter_prev(msg, end);
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 }
 
 static void sk_msg_shift_right(struct sk_msg *msg, int i)
 {
 	struct scatterlist tmp, sge;
+	bool tmp_copy, sge_copy;
 
 	sk_msg_iter_next(msg, end);
 	sge = sk_msg_elem_cpy(msg, i);
+	sge_copy = sk_msg_elem_is_copy(msg, i);
 	sk_msg_iter_var_next(i);
 	tmp = sk_msg_elem_cpy(msg, i);
+	tmp_copy = sk_msg_elem_is_copy(msg, i);
 
 	while (i != msg->sg.end) {
 		msg->sg.data[i] = sge;
+		if (sge_copy)
+			sk_msg_set_elem_copy(msg, i);
+		else
+			sk_msg_clear_elem_copy(msg, i);
 		sk_msg_iter_var_next(i);
 		sge = tmp;
+		sge_copy = tmp_copy;
 		tmp = sk_msg_elem_cpy(msg, i);
+		tmp_copy = sk_msg_elem_is_copy(msg, i);
 	}
+	sk_msg_clear_elem_copy(msg, msg->sg.end);
 }
 
 BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
@@ -2992,8 +3063,10 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
 	 */
 	if (start != offset) {
 		struct scatterlist *nsge, *sge = sk_msg_elem(msg, i);
+		bool sge_copy = sk_msg_elem_is_copy(msg, i);
 		int a = start - offset;
 		int b = sge->length - pop - a;
+		u32 sge_idx = i;
 
 		sk_msg_iter_var_next(i);
 
@@ -3006,6 +3079,10 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
 				sg_set_page(nsge,
 					    sg_page(sge),
 					    b, sge->offset + pop + a);
+				if (sge_copy)
+					sk_msg_set_elem_copy(msg, i);
+				else
+					sk_msg_clear_elem_copy(msg, i);
 			} else {
 				struct page *page, *orig;
 				u8 *to, *from;
@@ -3022,6 +3099,7 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
 				memcpy(to, from, a);
 				memcpy(to + a, from + a + pop, b);
 				sg_set_page(sge, page, a + b, 0);
+				sk_msg_clear_elem_copy(msg, sge_idx);
 				put_page(orig);
 			}
 			pop = 0;
-- 
2.53.0