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@@ -1,85 +0,0 @@
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-From: Liang Chen <[email protected]>
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-Date: Thu, 13 Apr 2023 17:03:53 +0800
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-Subject: [PATCH] skbuff: Fix a race between coalescing and releasing SKBs
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-
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-Commit 1effe8ca4e34 ("skbuff: fix coalescing for page_pool fragment
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-recycling") allowed coalescing to proceed with non page pool page and page
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-pool page when @from is cloned, i.e.
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-
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-to->pp_recycle --> false
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-from->pp_recycle --> true
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-skb_cloned(from) --> true
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-
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-However, it actually requires skb_cloned(@from) to hold true until
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-coalescing finishes in this situation. If the other cloned SKB is
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-released while the merging is in process, from_shinfo->nr_frags will be
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-set to 0 toward the end of the function, causing the increment of frag
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-page _refcount to be unexpectedly skipped resulting in inconsistent
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-reference counts. Later when SKB(@to) is released, it frees the page
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-directly even though the page pool page is still in use, leading to
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-use-after-free or double-free errors. So it should be prohibited.
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-
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-The double-free error message below prompted us to investigate:
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-BUG: Bad page state in process swapper/1 pfn:0e0d1
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-page:00000000c6548b28 refcount:-1 mapcount:0 mapping:0000000000000000
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-index:0x2 pfn:0xe0d1
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-flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff)
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-raw: 000fffffc0000000 0000000000000000 ffffffff00000101 0000000000000000
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-raw: 0000000000000002 0000000000000000 ffffffffffffffff 0000000000000000
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-page dumped because: nonzero _refcount
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-
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-CPU: 1 PID: 0 Comm: swapper/1 Tainted: G E 6.2.0+
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-Call Trace:
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- <IRQ>
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-dump_stack_lvl+0x32/0x50
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-bad_page+0x69/0xf0
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-free_pcp_prepare+0x260/0x2f0
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-free_unref_page+0x20/0x1c0
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-skb_release_data+0x10b/0x1a0
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-napi_consume_skb+0x56/0x150
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-net_rx_action+0xf0/0x350
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-? __napi_schedule+0x79/0x90
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-__do_softirq+0xc8/0x2b1
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-__irq_exit_rcu+0xb9/0xf0
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-common_interrupt+0x82/0xa0
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-</IRQ>
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-<TASK>
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-asm_common_interrupt+0x22/0x40
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-RIP: 0010:default_idle+0xb/0x20
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-
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-Fixes: 53e0961da1c7 ("page_pool: add frag page recycling support in page pool")
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-Signed-off-by: Liang Chen <[email protected]>
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-Reviewed-by: Eric Dumazet <[email protected]>
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-Link: https://lore.kernel.org/r/[email protected]
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-Signed-off-by: Jakub Kicinski <[email protected]>
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----
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-
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---- a/net/core/skbuff.c
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-+++ b/net/core/skbuff.c
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-@@ -5397,18 +5397,18 @@ bool skb_try_coalesce(struct sk_buff *to
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- if (skb_cloned(to))
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- return false;
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-
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-- /* In general, avoid mixing slab allocated and page_pool allocated
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-- * pages within the same SKB. However when @to is not pp_recycle and
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-- * @from is cloned, we can transition frag pages from page_pool to
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-- * reference counted.
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-- *
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-- * On the other hand, don't allow coalescing two pp_recycle SKBs if
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-- * @from is cloned, in case the SKB is using page_pool fragment
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-+ /* In general, avoid mixing page_pool and non-page_pool allocated
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-+ * pages within the same SKB. Additionally avoid dealing with clones
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-+ * with page_pool pages, in case the SKB is using page_pool fragment
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- * references (PP_FLAG_PAGE_FRAG). Since we only take full page
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- * references for cloned SKBs at the moment that would result in
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- * inconsistent reference counts.
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-+ * In theory we could take full references if @from is cloned and
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-+ * !@to->pp_recycle but its tricky (due to potential race with
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-+ * the clone disappearing) and rare, so not worth dealing with.
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- */
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-- if (to->pp_recycle != (from->pp_recycle && !skb_cloned(from)))
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-+ if (to->pp_recycle != from->pp_recycle ||
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-+ (from->pp_recycle && skb_cloned(from)))
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- return false;
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-
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- if (len <= skb_tailroom(to)) {
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