diff options
| author | Marco Elver <elver@google.com> | 2021-02-01 17:04:20 +0100 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-02-02 17:36:12 -0800 |
| commit | 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 (patch) | |
| tree | 15723ada024ebc1acff882732cd9b165eeee5266 /net/core/skbuff.c | |
| parent | ec99a470c7d5517c97dee6dd7953275a92c63834 (diff) | |
net: fix up truesize of cloned skb in skb_prepare_for_shift()
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@elver.google.com
Reported-by: syzbot+7b99aafdcc2eedea6178@syzkaller.appspotmail.com
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20210201160420.2826895-1-elver@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/core/skbuff.c')
| -rw-r--r-- | net/core/skbuff.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 2af12f7e170c..3787093239f5 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3289,7 +3289,19 @@ 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; } /** |