This is a note to let you know that I've just added the patch titled
net: fix up truesize of cloned skb in skb_prepare_for_shift()
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-fix-up-truesize-of-cloned-skb-in-skb_prepare_for_shift.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 Mon Sep 17 00:00:00 2001
From: Marco Elver <elver@xxxxxxxxxx>
Date: Mon, 1 Feb 2021 17:04:20 +0100
Subject: net: fix up truesize of cloned skb in skb_prepare_for_shift()
From: Marco Elver <elver@xxxxxxxxxx>
commit 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 upstream.
Avoid the assumption that ksize(kmalloc(S)) == ksize(kmalloc(S)): when
cloning an skb, save and restore truesize after pskb_expand_head(). This
can occur if the allocator decides to service an allocation of the same
size differently (e.g. use a different size class, or pass the
allocation on to KFENCE).
Because truesize is used for bookkeeping (such as sk_wmem_queued), a
modified truesize of a cloned skb may result in corrupt bookkeeping and
relevant warnings (such as in sk_stream_kill_queues()).
Link: https://lkml.kernel.org/r/X9JR/J6dMMOy1obu@xxxxxxxxxxxxxxxx
Reported-by: syzbot+7b99aafdcc2eedea6178@xxxxxxxxxxxxxxxxxxxxxxxxx
Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210201160420.2826895-1-elver@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/skbuff.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3292,7 +3292,19 @@ EXPORT_SYMBOL(skb_split);
*/
static int skb_prepare_for_shift(struct sk_buff *skb)
{
- return skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
+ int ret = 0;
+
+ if (skb_cloned(skb)) {
+ /* Save and restore truesize: pskb_expand_head() may reallocate
+ * memory where ksize(kmalloc(S)) != ksize(kmalloc(S)), but we
+ * cannot change truesize at this point.
+ */
+ unsigned int save_truesize = skb->truesize;
+
+ ret = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
+ skb->truesize = save_truesize;
+ }
+ return ret;
}
/**
Patches currently in stable-queue which might be from elver@xxxxxxxxxx are
queue-5.11/net-fix-up-truesize-of-cloned-skb-in-skb_prepare_for_shift.patch
