[PATCH 5.15.y 0/4] net/sched: fix pedit partial COW leading to page cache corruption

[PATCH 5.15.y 0/4] net/sched: fix pedit partial COW leading to page cache corruption

[Wentao Guan]

Fixes CVE-2026-46331: net/sched: fix pedit partial COW leading to page cache corruption

Link: https://lore.kernel.org/all/2026061625-CVE-2026-46331-47be@gregkh/

Pedro Tammela (3):
  net/sched: act_pedit: check static offsets a priori
  net/sched: act_pedit: rate limit datapath messages
  net/sched: act_pedit: free pedit keys on bail from offset check

Rajat Gupta (1):
  net/sched: fix pedit partial COW leading to page cache corruption

 include/net/tc_act/tc_pedit.h |   1 -
 net/sched/act_pedit.c         | 101 +++++++++++++++++++---------------
 2 files changed, 57 insertions(+), 45 deletions(-)

-- 
2.30.2

[PATCH 5.15.y 1/4] net/sched: act_pedit: check static offsets a priori

[Wentao Guan]

From: Pedro Tammela <pctammela@mojatatu.com>

[ Upstream commit e1201bc781c28766720e78a5e099ffa568be4d74 ]

Static key offsets should always be on 32 bit boundaries. Validate them on
create/update time for static offsets and move the datapath validation
for runtime offsets only.

iproute2 already errors out if a given offset and data size cannot be
packed to a 32 bit boundary. This change will make sure users which
create/update pedit instances directly via netlink also error out,
instead of finding out when packets are traversing.

Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit e1201bc781c28766720e78a5e099ffa568be4d74)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
---
 net/sched/act_pedit.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index e77da0545b553..8679e87d774d3 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -250,8 +250,16 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 	memcpy(nparms->tcfp_keys, parm->keys, ksize);
 
 	for (i = 0; i < nparms->tcfp_nkeys; ++i) {
+		u32 offmask = nparms->tcfp_keys[i].offmask;
 		u32 cur = nparms->tcfp_keys[i].off;
 
+		/* The AT option can be added to static offsets in the datapath */
+		if (!offmask && cur % 4) {
+			NL_SET_ERR_MSG_MOD(extack, "Offsets must be on 32bit boundaries");
+			ret = -EINVAL;
+			goto put_chain;
+		}
+
 		/* sanitize the shift value for any later use */
 		nparms->tcfp_keys[i].shift = min_t(size_t,
 						   BITS_PER_TYPE(int) - 1,
@@ -260,7 +268,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 		/* The AT option can read a single byte, we can bound the actual
 		 * value with uchar max.
 		 */
-		cur += (0xff & nparms->tcfp_keys[i].offmask) >> nparms->tcfp_keys[i].shift;
+		cur += (0xff & offmask) >> nparms->tcfp_keys[i].shift;
 
 		/* Each key touches 4 bytes starting from the computed offset */
 		nparms->tcfp_off_max_hint =
@@ -429,12 +437,12 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 					       sizeof(_d), &_d);
 			if (!d)
 				goto bad;
-			offset += (*d & tkey->offmask) >> tkey->shift;
-		}
 
-		if (offset % 4) {
-			pr_info("tc action pedit offset must be on 32 bit boundaries\n");
-			goto bad;
+			offset += (*d & tkey->offmask) >> tkey->shift;
+			if (offset % 4) {
+				pr_info("tc action pedit offset must be on 32 bit boundaries\n");
+				goto bad;
+			}
 		}
 
 		if (!offset_valid(skb, hoffset + offset)) {
-- 
2.30.2

[PATCH 5.15.y 2/4] net/sched: act_pedit: rate limit datapath messages

[Wentao Guan]

From: Pedro Tammela <pctammela@mojatatu.com>

[ Upstream commit e3c9673e2f6e1b3aa4bb87c570336e10f364c28a ]

Unbounded info messages in the pedit datapath can flood the printk
ring buffer quite easily depending on the action created.
As these messages are informational, usually printing some, not all,
is enough to bring attention to the real issue.

Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit e3c9673e2f6e1b3aa4bb87c570336e10f364c28a)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
---
 net/sched/act_pedit.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index 8679e87d774d3..46436b7641c14 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -429,8 +429,8 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 			u8 *d, _d;
 
 			if (!offset_valid(skb, hoffset + tkey->at)) {
-				pr_info("tc action pedit 'at' offset %d out of bounds\n",
-					hoffset + tkey->at);
+				pr_info_ratelimited("tc action pedit 'at' offset %d out of bounds\n",
+						    hoffset + tkey->at);
 				goto bad;
 			}
 			d = skb_header_pointer(skb, hoffset + tkey->at,
@@ -440,14 +440,13 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 
 			offset += (*d & tkey->offmask) >> tkey->shift;
 			if (offset % 4) {
-				pr_info("tc action pedit offset must be on 32 bit boundaries\n");
+				pr_info_ratelimited("tc action pedit offset must be on 32 bit boundaries\n");
 				goto bad;
 			}
 		}
 
 		if (!offset_valid(skb, hoffset + offset)) {
-			pr_info("tc action pedit offset %d out of bounds\n",
-				hoffset + offset);
+			pr_info_ratelimited("tc action pedit offset %d out of bounds\n", hoffset + offset);
 			goto bad;
 		}
 
@@ -464,8 +463,7 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 			val = (*ptr + tkey->val) & ~tkey->mask;
 			break;
 		default:
-			pr_info("tc action pedit bad command (%d)\n",
-				cmd);
+			pr_info_ratelimited("tc action pedit bad command (%d)\n", cmd);
 			goto bad;
 		}
 
-- 
2.30.2

[PATCH 5.15.y 3/4] net/sched: fix pedit partial COW leading to page cache corruption

[Wentao Guan]

From: Rajat Gupta <rajat.gupta@oss.qualcomm.com>

[ Upstream commit 899ee91156e57784090c5565e4f31bd7dbffbc5a ]

tcf_pedit_act() computes the COW range for skb_ensure_writable()
once before the key loop using tcfp_off_max_hint, but the hint does
not account for the runtime header offset added by typed keys. This
can leave part of the write region un-COW'd.

Fix by moving skb_ensure_writable() inside the per-key loop where
the actual write offset is known, and add overflow checking on the
offset arithmetic. For negative offsets (e.g. Ethernet header edits
at ingress), use skb_cow() to COW the headroom instead. Guard
offset_valid() against INT_MIN, where negation is undefined.

Fixes: 8b796475fd78 ("net/sched: act_pedit: really ensure the skb is writable")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Reported-by: Keenan Dong <keenanat2000@gmail.com>
Reported-by: Han Guidong <2045gemini@gmail.com>
Reported-by: Zhang Cen <rollkingzzc@gmail.com>
Reviewed-by: Han Guidong <2045gemini@gmail.com>
Tested-by: Han Guidong <2045gemini@gmail.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Tested-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Tested-by: Toke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Tested-by: Victor Nogueira <victor@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Rajat Gupta <rajat.gupta@oss.qualcomm.com>
Link: https://patch.msgid.link/20260531123221.48732-1-jhs@mojatatu.com
[rename include file from linux/unaligned.h to asm/unaligned.h]
Conflicts:
	include/net/tc_act/tc_pedit.h
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
---
 include/net/tc_act/tc_pedit.h |  1 -
 net/sched/act_pedit.c         | 77 +++++++++++++++++++----------------
 2 files changed, 41 insertions(+), 37 deletions(-)

diff --git a/include/net/tc_act/tc_pedit.h b/include/net/tc_act/tc_pedit.h
index 83fe399317818..a26d4cd3b8d6f 100644
--- a/include/net/tc_act/tc_pedit.h
+++ b/include/net/tc_act/tc_pedit.h
@@ -14,7 +14,6 @@ struct tcf_pedit_key_ex {
 struct tcf_pedit_parms {
 	struct tc_pedit_key	*tcfp_keys;
 	struct tcf_pedit_key_ex	*tcfp_keys_ex;
-	u32 tcfp_off_max_hint;
 	unsigned char tcfp_nkeys;
 	unsigned char tcfp_flags;
 	struct rcu_head rcu;
diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index 46436b7641c14..8f50cbdd5aff9 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -16,6 +16,8 @@
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/slab.h>
+#include <linux/overflow.h>
+#include <asm/unaligned.h>
 #include <net/ipv6.h>
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
@@ -237,7 +239,6 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 		goto out_free_ex;
 	}
 
-	nparms->tcfp_off_max_hint = 0;
 	nparms->tcfp_flags = parm->flags;
 	nparms->tcfp_nkeys = parm->nkeys;
 
@@ -265,14 +266,6 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 						   BITS_PER_TYPE(int) - 1,
 						   nparms->tcfp_keys[i].shift);
 
-		/* The AT option can read a single byte, we can bound the actual
-		 * value with uchar max.
-		 */
-		cur += (0xff & offmask) >> nparms->tcfp_keys[i].shift;
-
-		/* Each key touches 4 bytes starting from the computed offset */
-		nparms->tcfp_off_max_hint =
-			max(nparms->tcfp_off_max_hint, cur + 4);
 	}
 
 	p = to_pedit(*a);
@@ -313,15 +306,12 @@ static void tcf_pedit_cleanup(struct tc_action *a)
 		call_rcu(&parms->rcu, tcf_pedit_cleanup_rcu);
 }
 
-static bool offset_valid(struct sk_buff *skb, int offset)
+static bool offset_valid(struct sk_buff *skb, int offset, int len)
 {
-	if (offset > 0 && offset > skb->len)
-		return false;
-
-	if  (offset < 0 && -offset > skb_headroom(skb))
+	if (offset < -(int)skb_headroom(skb))
 		return false;
 
-	return true;
+	return offset <= (int)skb->len - len;
 }
 
 static int pedit_l4_skb_offset(struct sk_buff *skb, int *hoffset, const int header_type)
@@ -387,18 +377,10 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 	struct tcf_pedit_key_ex *tkey_ex;
 	struct tcf_pedit_parms *parms;
 	struct tc_pedit_key *tkey;
-	u32 max_offset;
 	int i;
 
 	parms = rcu_dereference_bh(p->parms);
 
-	max_offset = (skb_transport_header_was_set(skb) ?
-		      skb_transport_offset(skb) :
-		      skb_network_offset(skb)) +
-		     parms->tcfp_off_max_hint;
-	if (skb_ensure_writable(skb, min(skb->len, max_offset)))
-		goto done;
-
 	tcf_lastuse_update(&p->tcf_tm);
 	tcf_action_update_bstats(&p->common, skb);
 
@@ -406,10 +388,11 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 	tkey_ex = parms->tcfp_keys_ex;
 
 	for (i = parms->tcfp_nkeys; i > 0; i--, tkey++) {
+		int write_offset, write_len;
 		int offset = tkey->off;
 		int hoffset = 0;
-		u32 *ptr, hdata;
-		u32 val;
+		u32 cur_val, val;
+		u32 *ptr;
 		int rc;
 
 		if (tkey_ex) {
@@ -427,13 +410,15 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 
 		if (tkey->offmask) {
 			u8 *d, _d;
+			int at_offset;
 
-			if (!offset_valid(skb, hoffset + tkey->at)) {
+			if (check_add_overflow(hoffset, (int)tkey->at, &at_offset) ||
+			    !offset_valid(skb, at_offset, sizeof(_d))) {
 				pr_info_ratelimited("tc action pedit 'at' offset %d out of bounds\n",
 						    hoffset + tkey->at);
 				goto bad;
 			}
-			d = skb_header_pointer(skb, hoffset + tkey->at,
+			d = skb_header_pointer(skb, at_offset,
 					       sizeof(_d), &_d);
 			if (!d)
 				goto bad;
@@ -445,31 +430,51 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 			}
 		}
 
-		if (!offset_valid(skb, hoffset + offset)) {
-			pr_info_ratelimited("tc action pedit offset %d out of bounds\n", hoffset + offset);
+		if (check_add_overflow(hoffset, offset, &write_offset)) {
+			pr_info_ratelimited("tc action pedit offset overflow\n");
 			goto bad;
 		}
 
-		ptr = skb_header_pointer(skb, hoffset + offset,
-					 sizeof(hdata), &hdata);
-		if (!ptr)
+		if (!offset_valid(skb, write_offset, sizeof(*ptr))) {
+			pr_info_ratelimited("tc action pedit offset %d out of bounds\n",
+					    write_offset);
 			goto bad;
+		}
+
+		if (write_offset < 0) {
+			if (skb_cow(skb, -write_offset))
+				goto bad;
+			if (write_offset + (int)sizeof(*ptr) > 0) {
+				if (skb_ensure_writable(skb,
+							min_t(int, skb->len,
+							      write_offset + (int)sizeof(*ptr))))
+					goto bad;
+			}
+		} else {
+			if (check_add_overflow(write_offset, (int)sizeof(*ptr),
+					       &write_len))
+				goto bad;
+			if (skb_ensure_writable(skb, min_t(int, skb->len,
+							   write_len)))
+				goto bad;
+		}
+
+		ptr = (u32 *)(skb->data + write_offset);
+		cur_val = get_unaligned(ptr);
 		/* just do it, baby */
 		switch (cmd) {
 		case TCA_PEDIT_KEY_EX_CMD_SET:
 			val = tkey->val;
 			break;
 		case TCA_PEDIT_KEY_EX_CMD_ADD:
-			val = (*ptr + tkey->val) & ~tkey->mask;
+			val = (cur_val + tkey->val) & ~tkey->mask;
 			break;
 		default:
 			pr_info_ratelimited("tc action pedit bad command (%d)\n", cmd);
 			goto bad;
 		}
 
-		*ptr = ((*ptr & tkey->mask) ^ val);
-		if (ptr == &hdata)
-			skb_store_bits(skb, hoffset + offset, ptr, 4);
+		put_unaligned((cur_val & tkey->mask) ^ val, ptr);
 	}
 
 	goto done;
-- 
2.30.2

[PATCH 5.15.y 4/4] net/sched: act_pedit: free pedit keys on bail from offset check

[Wentao Guan]

From: Pedro Tammela <pctammela@mojatatu.com>

Ido Schimmel reports a memleak on a syzkaller instance:
   BUG: memory leak
   unreferenced object 0xffff88803d45e400 (size 1024):
     comm "syz-executor292", pid 563, jiffies 4295025223 (age 51.781s)
     hex dump (first 32 bytes):
       28 bd 70 00 fb db df 25 02 00 14 1f ff 02 00 02  (.p....%........
       00 32 00 00 1f 00 00 00 ac 14 14 3e 08 00 07 00  .2.........>....
     backtrace:
       [<ffffffff81bd0f2c>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
       [<ffffffff81bd0f2c>] slab_post_alloc_hook mm/slab.h:772 [inline]
       [<ffffffff81bd0f2c>] slab_alloc_node mm/slub.c:3452 [inline]
       [<ffffffff81bd0f2c>] __kmem_cache_alloc_node+0x25c/0x320 mm/slub.c:3491
       [<ffffffff81a865d9>] __do_kmalloc_node mm/slab_common.c:966 [inline]
       [<ffffffff81a865d9>] __kmalloc+0x59/0x1a0 mm/slab_common.c:980
       [<ffffffff83aa85c3>] kmalloc include/linux/slab.h:584 [inline]
       [<ffffffff83aa85c3>] tcf_pedit_init+0x793/0x1ae0 net/sched/act_pedit.c:245
       [<ffffffff83a90623>] tcf_action_init_1+0x453/0x6e0 net/sched/act_api.c:1394
       [<ffffffff83a90e58>] tcf_action_init+0x5a8/0x950 net/sched/act_api.c:1459
       [<ffffffff83a96258>] tcf_action_add+0x118/0x4e0 net/sched/act_api.c:1985
       [<ffffffff83a96997>] tc_ctl_action+0x377/0x490 net/sched/act_api.c:2044
       [<ffffffff83920a8d>] rtnetlink_rcv_msg+0x46d/0xd70 net/core/rtnetlink.c:6395
       [<ffffffff83b24305>] netlink_rcv_skb+0x185/0x490 net/netlink/af_netlink.c:2575
       [<ffffffff83901806>] rtnetlink_rcv+0x26/0x30 net/core/rtnetlink.c:6413
       [<ffffffff83b21cae>] netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
       [<ffffffff83b21cae>] netlink_unicast+0x5be/0x8a0 net/netlink/af_netlink.c:1365
       [<ffffffff83b2293f>] netlink_sendmsg+0x9af/0xed0 net/netlink/af_netlink.c:1942
       [<ffffffff8380c39f>] sock_sendmsg_nosec net/socket.c:724 [inline]
       [<ffffffff8380c39f>] sock_sendmsg net/socket.c:747 [inline]
       [<ffffffff8380c39f>] ____sys_sendmsg+0x3ef/0xaa0 net/socket.c:2503
       [<ffffffff838156d2>] ___sys_sendmsg+0x122/0x1c0 net/socket.c:2557
       [<ffffffff8381594f>] __sys_sendmsg+0x11f/0x200 net/socket.c:2586
       [<ffffffff83815ab0>] __do_sys_sendmsg net/socket.c:2595 [inline]
       [<ffffffff83815ab0>] __se_sys_sendmsg net/socket.c:2593 [inline]
       [<ffffffff83815ab0>] __x64_sys_sendmsg+0x80/0xc0 net/socket.c:2593

The recently added static offset check missed a free to the key buffer when
bailing out on error.

Fixes: e1201bc781c2 ("net/sched: act_pedit: check static offsets a priori")
Reported-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/20230425144725.669262-1-pctammela@mojatatu.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
(cherry picked from commit 1b483d9f5805c7e3d628d4995e97f4311fcb82eb)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
---
 net/sched/act_pedit.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index 8f50cbdd5aff9..8e69b6120b28f 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -258,7 +258,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 		if (!offmask && cur % 4) {
 			NL_SET_ERR_MSG_MOD(extack, "Offsets must be on 32bit boundaries");
 			ret = -EINVAL;
-			goto put_chain;
+			goto out_free_keys;
 		}
 
 		/* sanitize the shift value for any later use */
@@ -283,6 +283,8 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 
 	return ret;
 
+out_free_keys:
+	kfree(nparms->tcfp_keys);
 put_chain:
 	if (goto_ch)
 		tcf_chain_put_by_act(goto_ch);
-- 
2.30.2

Re: [PATCH 5.15.y 0/4] net/sched: fix pedit partial COW leading to page cache corruption

[Sasha Levin]

>  [PATCH 5.15.y 0/4] net/sched: fix pedit partial COW leading to page
>  cache corruption

Queued the series for 5.15, thanks.

--
Thanks,
Sasha