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Eric Dumazet 3261400639 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 `84ce071e38` ("net: introduce __skb_fill_page_desc_noacc") as a prereq. Race is more probable after commit `c07aea3ef4` ("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 Fixes: `c07aea3ef4` ("mm: add a signature in struct page") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Shakeel Butt <shakeelb@google.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2022-09-02 12:29:02 +01:00
arch	Misc fixes:	2022-08-28 10:10:23 -07:00
block	block-6.0-2022-08-26	2022-08-26 11:05:54 -07:00
certs	Kbuild updates for v5.20	2022-08-10 10:40:41 -07:00
crypto	crypto: blake2b: effectively disable frame size warning	2022-08-10 17:59:11 -07:00
Documentation	Networking fixes for 6.0-rc4, including fixes from bluetooth, bpf	2022-09-01 09:20:42 -07:00
drivers	Revert "net: phy: meson-gxl: improve link-up behavior"	2022-09-01 20:55:12 -07:00
fs	cachefiles: make on-demand request distribution fairer	2022-08-31 16:41:10 +01:00
include	tcp: TX zerocopy should not sense pfmemalloc status	2022-09-02 12:29:02 +01:00
init	arm64 fixes for -rc3	2022-08-26 11:32:53 -07:00
io_uring	lsm/stable-6.0 PR 20220829	2022-08-31 09:23:16 -07:00
ipc	Updates to various subsystems which I help look after. lib, ocfs2,	2022-08-07 10:03:24 -07:00
kernel	Networking fixes for 6.0-rc4, including fixes from bluetooth, bpf	2022-09-01 09:20:42 -07:00
lib	This push fixes a boot performance regression due to an unnecessary	2022-08-31 09:47:06 -07:00
LICENSES	LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers	2021-12-16 14:33:10 +01:00
mm	slab fixes for 6.0-rc4	2022-09-01 09:14:56 -07:00
net	tcp: TX zerocopy should not sense pfmemalloc status	2022-09-02 12:29:02 +01:00
samples	Tracing updates for 5.20 / 6.0	2022-08-05 09:41:12 -07:00
scripts	asm goto: eradicate CC_HAS_ASM_GOTO	2022-08-21 10:06:28 -07:00
security	lsm/stable-6.0 PR 20220829	2022-08-31 09:23:16 -07:00
sound	ALSA: usb-audio: Add quirk for LH Labs Geek Out HD Audio 1V5	2022-08-28 09:42:14 +02:00
tools	Networking fixes for 6.0-rc4, including fixes from bluetooth, bpf	2022-09-01 09:20:42 -07:00
usr	Not a lot of material this cycle. Many singleton patches against various	2022-05-27 11:22:03 -07:00
virt	KVM: Drop unnecessary initialization of "ops" in kvm_ioctl_create_device()	2022-08-19 04:05:43 -04:00
.clang-format	PCI/DOE: Add DOE mailbox support functions	2022-07-19 15:38:04 -07:00
.cocciconfig
.get_maintainer.ignore	get_maintainer: add Alan to .get_maintainer.ignore	2022-08-20 15:17:44 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	kbuild: split the second line of .mod into .usyms	2022-05-08 03:16:59 +09:00
.mailmap	.mailmap: update Luca Ceresoli's e-mail address	2022-08-28 14:02:46 -07:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	drm for 5.20/6.0	2022-08-03 19:52:08 -07:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	bitmap fixes for v6.0-rc3	2022-08-28 14:36:27 -07:00
Makefile	Linux 6.0-rc3	2022-08-28 15:05:29 -07:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.