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Message-ID: <167542916933.1167230.1244118780145312645.stgit@firesoul>
Date: Fri, 03 Feb 2023 13:59:29 +0100
From: Jesper Dangaard Brouer <brouer@...hat.com>
To: netdev@...r.kernel.org
Cc: Jesper Dangaard Brouer <brouer@...hat.com>,
Jakub Kicinski <kuba@...nel.org>,
"David S. Miller" <davem@...emloft.net>, edumazet@...gle.com,
pabeni@...hat.com
Subject: [PATCH net-next V2] net: introduce skb_poison_list and use in
kfree_skb_list
First user of skb_poison_list is in kfree_skb_list_reason, to catch bugs
earlier like introduced in commit eedade12f4cb ("net: kfree_skb_list use
kmem_cache_free_bulk"). For completeness mentioned bug have been fixed in
commit f72ff8b81ebc ("net: fix kfree_skb_list use of skb_mark_not_on_list").
In case of a bug like mentioned commit we would have seen OOPS with:
general protection fault, probably for non-canonical address 0xdead000000000870
And content of one the registers e.g. R13: dead000000000800
In this case skb->len is at offset 112 bytes (0x70) why fault happens at
0x800+0x70 = 0x870
Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
include/linux/poison.h | 3 +++
include/linux/skbuff.h | 7 +++++++
net/core/skbuff.c | 4 +++-
3 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 2d3249eb0e62..2823f90fdab4 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -81,6 +81,9 @@
/********** net/core/page_pool.c **********/
#define PP_SIGNATURE (0x40 + POISON_POINTER_DELTA)
+/********** net/core/skbuff.c **********/
+#define SKB_LIST_POISON_NEXT ((void *)(0x800 + POISON_POINTER_DELTA))
+
/********** kernel/bpf/ **********/
#define BPF_PTR_POISON ((void *)(0xeB9FUL + POISON_POINTER_DELTA))
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5ba12185f43e..1fa95b916342 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1738,6 +1738,13 @@ static inline void skb_mark_not_on_list(struct sk_buff *skb)
skb->next = NULL;
}
+static inline void skb_poison_list(struct sk_buff *skb)
+{
+#ifdef CONFIG_DEBUG_NET
+ skb->next = SKB_LIST_POISON_NEXT;
+#endif
+}
+
/* Iterate through singly-linked GSO fragments of an skb. */
#define skb_list_walk_safe(first, skb, next_skb) \
for ((skb) = (first), (next_skb) = (skb) ? (skb)->next : NULL; (skb); \
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 44a19805c355..624e9e4ec116 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1000,8 +1000,10 @@ kfree_skb_list_reason(struct sk_buff *segs, enum skb_drop_reason reason)
while (segs) {
struct sk_buff *next = segs->next;
- if (__kfree_skb_reason(segs, reason))
+ if (__kfree_skb_reason(segs, reason)) {
+ skb_poison_list(segs);
kfree_skb_add_bulk(segs, &sa, reason);
+ }
segs = next;
}
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