CVE-2023-53186

In the Linux kernel, the following vulnerability has been resolved:

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