From: Willem de Bruijn Date: Thu, 28 Dec 2017 17:38:13 +0000 (-0500) Subject: skbuff: in skb_copy_ubufs unclone before releasing zerocopy X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b9edd6bf0ccb2939a7716b80d3e73a24ead9fe62;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git skbuff: in skb_copy_ubufs unclone before releasing zerocopy skb_copy_ubufs must unclone before it is safe to modify its skb_shared_info with skb_zcopy_clear. Commit b90ddd568792 ("skbuff: skb_copy_ubufs must release uarg even without user frags") ensures that all skbs release their zerocopy state, even those without frags. But I forgot an edge case where such an skb arrives that is cloned. The stack does not build such packets. Vhost/tun skbs have their frags orphaned before cloning. TCP skbs only attach zerocopy state when a frag is added. But if TCP packets can be trimmed or linearized, this might occur. Tracing the code I found no instance so far (e.g., skb_linearize ends up calling skb_zcopy_clear if !skb->data_len). Still, it is non-obvious that no path exists. And it is fragile to rely on this. Fixes: b90ddd568792 ("skbuff: skb_copy_ubufs must release uarg even without user frags") Signed-off-by: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 4a10e96c6efc..15fa5baa8fae 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1181,12 +1181,12 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask) int i, new_frags; u32 d_off; - if (!num_frags) - goto release; - if (skb_shared(skb) || skb_unclone(skb, gfp_mask)) return -EINVAL; + if (!num_frags) + goto release; + new_frags = (__skb_pagelen(skb) + PAGE_SIZE - 1) >> PAGE_SHIFT; for (i = 0; i < new_frags; i++) { page = alloc_page(gfp_mask);