+++ /dev/null
-From: Liang Chen <liangchen.linux@gmail.com>
-Date: Thu, 13 Apr 2023 17:03:53 +0800
-Subject: [PATCH] skbuff: Fix a race between coalescing and releasing SKBs
-
-Commit 1effe8ca4e34 ("skbuff: fix coalescing for page_pool fragment
-recycling") allowed coalescing to proceed with non page pool page and page
-pool page when @from is cloned, i.e.
-
-to->pp_recycle --> false
-from->pp_recycle --> true
-skb_cloned(from) --> true
-
-However, it actually requires skb_cloned(@from) to hold true until
-coalescing finishes in this situation. If the other cloned SKB is
-released while the merging is in process, from_shinfo->nr_frags will be
-set to 0 toward the end of the function, causing the increment of frag
-page _refcount to be unexpectedly skipped resulting in inconsistent
-reference counts. Later when SKB(@to) is released, it frees the page
-directly even though the page pool page is still in use, leading to
-use-after-free or double-free errors. So it should be prohibited.
-
-The double-free error message below prompted us to investigate:
-BUG: Bad page state in process swapper/1 pfn:0e0d1
-page:00000000c6548b28 refcount:-1 mapcount:0 mapping:0000000000000000
-index:0x2 pfn:0xe0d1
-flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff)
-raw: 000fffffc0000000 0000000000000000 ffffffff00000101 0000000000000000
-raw: 0000000000000002 0000000000000000 ffffffffffffffff 0000000000000000
-page dumped because: nonzero _refcount
-
-CPU: 1 PID: 0 Comm: swapper/1 Tainted: G E 6.2.0+
-Call Trace:
- <IRQ>
-dump_stack_lvl+0x32/0x50
-bad_page+0x69/0xf0
-free_pcp_prepare+0x260/0x2f0
-free_unref_page+0x20/0x1c0
-skb_release_data+0x10b/0x1a0
-napi_consume_skb+0x56/0x150
-net_rx_action+0xf0/0x350
-? __napi_schedule+0x79/0x90
-__do_softirq+0xc8/0x2b1
-__irq_exit_rcu+0xb9/0xf0
-common_interrupt+0x82/0xa0
-</IRQ>
-<TASK>
-asm_common_interrupt+0x22/0x40
-RIP: 0010:default_idle+0xb/0x20
-
-Fixes: 53e0961da1c7 ("page_pool: add frag page recycling support in page pool")
-Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
-Reviewed-by: Eric Dumazet <edumazet@google.com>
-Link: https://lore.kernel.org/r/20230413090353.14448-1-liangchen.linux@gmail.com
-Signed-off-by: Jakub Kicinski <kuba@kernel.org>
----
-
---- a/net/core/skbuff.c
-+++ b/net/core/skbuff.c
-@@ -5397,18 +5397,18 @@ bool skb_try_coalesce(struct sk_buff *to
- if (skb_cloned(to))
- return false;
-
-- /* In general, avoid mixing slab allocated and page_pool allocated
-- * pages within the same SKB. However when @to is not pp_recycle and
-- * @from is cloned, we can transition frag pages from page_pool to
-- * reference counted.
-- *
-- * On the other hand, don't allow coalescing two pp_recycle SKBs if
-- * @from is cloned, in case the SKB is using page_pool fragment
-+ /* In general, avoid mixing page_pool and non-page_pool allocated
-+ * pages within the same SKB. Additionally avoid dealing with clones
-+ * with page_pool pages, in case the SKB is using page_pool fragment
- * references (PP_FLAG_PAGE_FRAG). Since we only take full page
- * references for cloned SKBs at the moment that would result in
- * inconsistent reference counts.
-+ * In theory we could take full references if @from is cloned and
-+ * !@to->pp_recycle but its tricky (due to potential race with
-+ * the clone disappearing) and rare, so not worth dealing with.
- */
-- if (to->pp_recycle != (from->pp_recycle && !skb_cloned(from)))
-+ if (to->pp_recycle != from->pp_recycle ||
-+ (from->pp_recycle && skb_cloned(from)))
- return false;
-
- if (len <= skb_tailroom(to)) {
projects / openwrt / staging / dedeckeh.git / blobdiff