ghsa-93vx-p2jx-wj6m
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
tcp: TX zerocopy should not sense pfmemalloc status
We got a recent syzbot report [1] showing a possible misuse of pfmemalloc page status in TCP zerocopy paths.
Indeed, for pages coming from user space or other layers, using page_is_pfmemalloc() is moot, and possibly could give false positives.
There has been attempts to make page_is_pfmemalloc() more robust, but not using it in the first place in this context is probably better, removing cpu cycles.
Note to stable teams :
You need to backport 84ce071e38a6 ("net: introduce __skb_fill_page_desc_noacc") as a prereq.
Race is more probable after commit c07aea3ef4d4 ("mm: add a signature in struct page") because page_is_pfmemalloc() is now using low order bit from page->lru.next, which can change more often than page->index.
Low order bit should never be set for lru.next (when used as an anchor in LRU list), so KCSAN report is mostly a false positive.
Backporting to older kernel versions seems not necessary.
[1] BUG: KCSAN: data-race in lru_add_fn / tcp_build_frag
write to 0xffffea0004a1d2c8 of 8 bytes by task 18600 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:105 [inline] lru_add_fn+0x440/0x520 mm/swap.c:228 folio_batch_move_lru+0x1e1/0x2a0 mm/swap.c:246 folio_batch_add_and_move mm/swap.c:263 [inline] folio_add_lru+0xf1/0x140 mm/swap.c:490 filemap_add_folio+0xf8/0x150 mm/filemap.c:948 __filemap_get_folio+0x510/0x6d0 mm/filemap.c:1981 pagecache_get_page+0x26/0x190 mm/folio-compat.c:104 grab_cache_page_write_begin+0x2a/0x30 mm/folio-compat.c:116 ext4_da_write_begin+0x2dd/0x5f0 fs/ext4/inode.c:2988 generic_perform_write+0x1d4/0x3f0 mm/filemap.c:3738 ext4_buffered_write_iter+0x235/0x3e0 fs/ext4/file.c:270 ext4_file_write_iter+0x2e3/0x1210 call_write_iter include/linux/fs.h:2187 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x468/0x760 fs/read_write.c:578 ksys_write+0xe8/0x1a0 fs/read_write.c:631 __do_sys_write fs/read_write.c:643 [inline] __se_sys_write fs/read_write.c:640 [inline] __x64_sys_write+0x3e/0x50 fs/read_write.c:640 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
read to 0xffffea0004a1d2c8 of 8 bytes by task 18611 on cpu 1: page_is_pfmemalloc include/linux/mm.h:1740 [inline] __skb_fill_page_desc include/linux/skbuff.h:2422 [inline] skb_fill_page_desc include/linux/skbuff.h:2443 [inline] tcp_build_frag+0x613/0xb20 net/ipv4/tcp.c:1018 do_tcp_sendpages+0x3e8/0xaf0 net/ipv4/tcp.c:1075 tcp_sendpage_locked net/ipv4/tcp.c:1140 [inline] tcp_sendpage+0x89/0xb0 net/ipv4/tcp.c:1150 inet_sendpage+0x7f/0xc0 net/ipv4/af_inet.c:833 kernel_sendpage+0x184/0x300 net/socket.c:3561 sock_sendpage+0x5a/0x70 net/socket.c:1054 pipe_to_sendpage+0x128/0x160 fs/splice.c:361 splice_from_pipe_feed fs/splice.c:415 [inline] __splice_from_pipe+0x222/0x4d0 fs/splice.c:559 splice_from_pipe fs/splice.c:594 [inline] generic_splice_sendpage+0x89/0xc0 fs/splice.c:743 do_splice_from fs/splice.c:764 [inline] direct_splice_actor+0x80/0xa0 fs/splice.c:931 splice_direct_to_actor+0x305/0x620 fs/splice.c:886 do_splice_direct+0xfb/0x180 fs/splice.c:974 do_sendfile+0x3bf/0x910 fs/read_write.c:1249 __do_sys_sendfile64 fs/read_write.c:1317 [inline] __se_sys_sendfile64 fs/read_write.c:1303 [inline] __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1303 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x0000000000000000 -> 0xffffea0004a1d288
Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 18611 Comm: syz-executor.4 Not tainted 6.0.0-rc2-syzkaller-00248-ge022620b5d05-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
{
"affected": [],
"aliases": [
"CVE-2022-48689"
],
"database_specific": {
"cwe_ids": [
"CWE-362"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-05-03T15:15:07Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: TX zerocopy should not sense pfmemalloc status\n\nWe got a recent syzbot report [1] showing a possible misuse\nof pfmemalloc page status in TCP zerocopy paths.\n\nIndeed, for pages coming from user space or other layers,\nusing page_is_pfmemalloc() is moot, and possibly could give\nfalse positives.\n\nThere has been attempts to make page_is_pfmemalloc() more robust,\nbut not using it in the first place in this context is probably better,\nremoving cpu cycles.\n\nNote to stable teams :\n\nYou need to backport 84ce071e38a6 (\"net: introduce\n__skb_fill_page_desc_noacc\") as a prereq.\n\nRace is more probable after commit c07aea3ef4d4\n(\"mm: add a signature in struct page\") because page_is_pfmemalloc()\nis now using low order bit from page-\u003elru.next, which can change\nmore often than page-\u003eindex.\n\nLow order bit should never be set for lru.next (when used as an anchor\nin LRU list), so KCSAN report is mostly a false positive.\n\nBackporting to older kernel versions seems not necessary.\n\n[1]\nBUG: KCSAN: data-race in lru_add_fn / tcp_build_frag\n\nwrite to 0xffffea0004a1d2c8 of 8 bytes by task 18600 on cpu 0:\n__list_add include/linux/list.h:73 [inline]\nlist_add include/linux/list.h:88 [inline]\nlruvec_add_folio include/linux/mm_inline.h:105 [inline]\nlru_add_fn+0x440/0x520 mm/swap.c:228\nfolio_batch_move_lru+0x1e1/0x2a0 mm/swap.c:246\nfolio_batch_add_and_move mm/swap.c:263 [inline]\nfolio_add_lru+0xf1/0x140 mm/swap.c:490\nfilemap_add_folio+0xf8/0x150 mm/filemap.c:948\n__filemap_get_folio+0x510/0x6d0 mm/filemap.c:1981\npagecache_get_page+0x26/0x190 mm/folio-compat.c:104\ngrab_cache_page_write_begin+0x2a/0x30 mm/folio-compat.c:116\next4_da_write_begin+0x2dd/0x5f0 fs/ext4/inode.c:2988\ngeneric_perform_write+0x1d4/0x3f0 mm/filemap.c:3738\next4_buffered_write_iter+0x235/0x3e0 fs/ext4/file.c:270\next4_file_write_iter+0x2e3/0x1210\ncall_write_iter include/linux/fs.h:2187 [inline]\nnew_sync_write fs/read_write.c:491 [inline]\nvfs_write+0x468/0x760 fs/read_write.c:578\nksys_write+0xe8/0x1a0 fs/read_write.c:631\n__do_sys_write fs/read_write.c:643 [inline]\n__se_sys_write fs/read_write.c:640 [inline]\n__x64_sys_write+0x3e/0x50 fs/read_write.c:640\ndo_syscall_x64 arch/x86/entry/common.c:50 [inline]\ndo_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80\nentry_SYSCALL_64_after_hwframe+0x63/0xcd\n\nread to 0xffffea0004a1d2c8 of 8 bytes by task 18611 on cpu 1:\npage_is_pfmemalloc include/linux/mm.h:1740 [inline]\n__skb_fill_page_desc include/linux/skbuff.h:2422 [inline]\nskb_fill_page_desc include/linux/skbuff.h:2443 [inline]\ntcp_build_frag+0x613/0xb20 net/ipv4/tcp.c:1018\ndo_tcp_sendpages+0x3e8/0xaf0 net/ipv4/tcp.c:1075\ntcp_sendpage_locked net/ipv4/tcp.c:1140 [inline]\ntcp_sendpage+0x89/0xb0 net/ipv4/tcp.c:1150\ninet_sendpage+0x7f/0xc0 net/ipv4/af_inet.c:833\nkernel_sendpage+0x184/0x300 net/socket.c:3561\nsock_sendpage+0x5a/0x70 net/socket.c:1054\npipe_to_sendpage+0x128/0x160 fs/splice.c:361\nsplice_from_pipe_feed fs/splice.c:415 [inline]\n__splice_from_pipe+0x222/0x4d0 fs/splice.c:559\nsplice_from_pipe fs/splice.c:594 [inline]\ngeneric_splice_sendpage+0x89/0xc0 fs/splice.c:743\ndo_splice_from fs/splice.c:764 [inline]\ndirect_splice_actor+0x80/0xa0 fs/splice.c:931\nsplice_direct_to_actor+0x305/0x620 fs/splice.c:886\ndo_splice_direct+0xfb/0x180 fs/splice.c:974\ndo_sendfile+0x3bf/0x910 fs/read_write.c:1249\n__do_sys_sendfile64 fs/read_write.c:1317 [inline]\n__se_sys_sendfile64 fs/read_write.c:1303 [inline]\n__x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1303\ndo_syscall_x64 arch/x86/entry/common.c:50 [inline]\ndo_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80\nentry_SYSCALL_64_after_hwframe+0x63/0xcd\n\nvalue changed: 0x0000000000000000 -\u003e 0xffffea0004a1d288\n\nReported by Kernel Concurrency Sanitizer on:\nCPU: 1 PID: 18611 Comm: syz-executor.4 Not tainted 6.0.0-rc2-syzkaller-00248-ge022620b5d05-dirty #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022",
"id": "GHSA-93vx-p2jx-wj6m",
"modified": "2024-06-03T18:53:46Z",
"published": "2024-05-03T15:30:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-48689"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3261400639463a853ba2b3be8bd009c2a8089775"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6730c48ed6b0cd939fc9b30b2d621ce0b89bea83"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8527c9a6bf8e54fef0a8d3d7d8874a48c725c915"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.