CVE-2022-50323

/// Technical description

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

net: do not sense pfmemalloc status in skb_append_pagefrags()

skb_append_pagefrags() is used by af_unix and udp sendpage()

implementation so far.

In commit 326140063946 ("tcp: TX zerocopy should not sense

pfmemalloc status") we explained why we should not sense

pfmemalloc status for pages owned by user space.

We should also use skb_fill_page_desc_noacc()

in skb_append_pagefrags() to avoid following KCSAN report:

BUG: KCSAN: data-race in lru_add_fn / skb_append_pagefrags

write to 0xffffea00058fc1c8 of 8 bytes by task 17319 on cpu 0:

__list_add include/linux/list.h:73 [inline]

list_add include/linux/list.h:88 [inline]

lruvec_add_folio include/linux/mm_inline.h:323 [inline]

lru_add_fn+0x327/0x410 mm/swap.c:228

folio_batch_move_lru+0x1e1/0x2a0 mm/swap.c:246

lru_add_drain_cpu+0x73/0x250 mm/swap.c:669

lru_add_drain+0x21/0x60 mm/swap.c:773

free_pages_and_swap_cache+0x16/0x70 mm/swap_state.c:311

tlb_batch_pages_flush mm/

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References