6.6-stable review patch. If anyone has any objections, please let me know.
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From: Florian Westphal fw@strlen.de
[ Upstream commit 2bbe3e5a2f4ef69d13be54f1cf895b4658287080 ]
syzkaller builds (CONFIG_DEBUG_NET=y) frequently trigger a debug hint in pskb_may_pull.
We'd like to retain this debug check because it might hint at integer overflows and other issues (kernel code should pull headers, not huge value).
In bpf case, this splat isn't interesting at all: such (nonsensical) bpf programs are typically generated by a fuzzer anyway.
Do what Eric suggested and suppress such warning.
For CONFIG_DEBUG_NET=n we don't need the extra check because pskb_may_pull will do the right thing: return an error without the WARN() backtrace.
Fixes: 219eee9c0d16 ("net: skbuff: add overflow debug check to pull/push helpers") Reported-by: syzbot+0c4150bff9fff3bf023c@syzkaller.appspotmail.com Suggested-by: Eric Dumazet edumazet@google.com Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Eric Dumazet edumazet@google.com Acked-by: Daniel Borkmann daniel@iogearbox.net Closes: https://syzkaller.appspot.com/bug?extid=0c4150bff9fff3bf023c Link: https://lore.kernel.org/netdev/9f254c96-54f2-4457-b7ab-1d9f6187939c@gmail.co... Link: https://lore.kernel.org/bpf/20240614101801.9496-1-fw@strlen.de Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/filter.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/net/core/filter.c b/net/core/filter.c index df4578219e82c..afe38b8dee024 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1657,6 +1657,11 @@ static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp); static inline int __bpf_try_make_writable(struct sk_buff *skb, unsigned int write_len) { +#ifdef CONFIG_DEBUG_NET + /* Avoid a splat in pskb_may_pull_reason() */ + if (write_len > INT_MAX) + return -EINVAL; +#endif return skb_ensure_writable(skb, write_len); }