kernel/linux.git/include/linux/skbuff.h, branch v5.19.13

tcp: TX zerocopy should not sense pfmemalloc status

2022-09-15T08:47:15+00:00

[ Upstream commit 3261400639463a853ba2b3be8bd009c2a8089775 ] 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 Fixes: c07aea3ef4d4 ("mm: add a signature in struct page") Reported-by: syzbot Signed-off-by: Eric Dumazet Cc: Shakeel Butt Reviewed-by: Shakeel Butt Signed-off-by: David S. Miller Signed-off-by: Sasha Levin

net: introduce __skb_fill_page_desc_noacc

2022-09-15T08:47:15+00:00

[ Upstream commit 84ce071e38a6e25ea3ea91188e5482ac1f17b3af ] Managed pages contain pinned userspace pages and controlled by upper layers, there is no need in tracking skb->pfmemalloc for them. Introduce a helper for filling frags but ignoring page tracking, it'll be needed later. Signed-off-by: Pavel Begunkov Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bpf: Don't redirect packets with invalid pkt_len

2022-09-05T08:31:28+00:00

commit fd1894224407c484f652ad456e1ce423e89bb3eb upstream. Syzbot found an issue [1]: fq_codel_drop() try to drop a flow whitout any skbs, that is, the flow->head is null. The root cause, as the [2] says, is because that bpf_prog_test_run_skb() run a bpf prog which redirects empty skbs. So we should determine whether the length of the packet modified by bpf prog or others like bpf_prog_test is valid before forwarding it directly. LINK: [1] https://syzkaller.appspot.com/bug?id=0b84da80c2917757915afa89f7738a9d16ec96c5 LINK: [2] https://www.spinics.net/lists/netdev/msg777503.html Reported-by: syzbot+7a12909485b94426aceb@syzkaller.appspotmail.com Signed-off-by: Zhengchao Shao Reviewed-by: Stanislav Fomichev Link: https://lore.kernel.org/r/20220715115559.139691-1-shaozhengchao@huawei.com Signed-off-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman

net: add debug info to __skb_pull()

2022-06-02T17:15:05+00:00

While analyzing yet another syzbot report, I found the following patch very useful. It allows to better understand what went wrong. This debug info is only enabled if CONFIG_DEBUG_NET=y, which is the case for syzbot builds. Signed-off-by: Eric Dumazet Acked-by: Willem de Bruijn Signed-off-by: Jakub Kicinski

net: skb: Remove skb_data_area_size()

2022-05-16T20:45:36+00:00

skb_data_area_size() is not needed. As Jakub pointed out [1]: For Rx, drivers can use the size passed during skb allocation or use skb_tailroom(). For Tx, drivers should use skb_headlen(). [1] https://lore.kernel.org/netdev/CAHNKnsTmH-rGgWi3jtyC=ktM1DW2W1VJkYoTMJV2Z_Bt498bsg@mail.gmail.com/ Signed-off-by: Ricardo Martinez Reviewed-by: Andy Shevchenko Reviewed-by: Sergey Ryazanov Signed-off-by: Jakub Kicinski

net: skb: change the definition SKB_DR_SET()

2022-05-16T09:47:43+00:00

The SKB_DR_OR() is used to set the drop reason to a value when it is not set or specified yet. SKB_NOT_DROPPED_YET should also be considered as not set. Reviewed-by: Jiang Biao Reviewed-by: Hao Peng Signed-off-by: Menglong Dong Signed-off-by: David S. Miller

skbuff: replace a BUG_ON() with the new DEBUG_NET_WARN_ON_ONCE()

2022-05-12T23:20:52+00:00

Very few drivers actually have Kconfig knobs for adding -DDEBUG. 8 according to a quick grep, while there are 93 users of skb_checksum_none_assert(). Switch to the new DEBUG_NET_WARN_ON_ONCE() to catch bad skbs. Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/20220511172305.1382810-1-kuba@kernel.org Signed-off-by: Jakub Kicinski

net: warn if transport header was not set

2022-05-11T11:44:16+00:00

Make sure skb_transport_header() and skb_transport_offset() uses are not fooled if the transport header has not been set. This change will likely expose existing bugs in linux networking stacks. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

skbuff: render the checksum comment to documentation

2022-05-11T00:48:37+00:00

Long time ago Tom added a giant comment to skbuff.h explaining checksums. Now that we have a place in Documentation for skbuff docs we should render it. Sprinkle some markup while at it. Reviewed-by: David Ahern Signed-off-by: Jakub Kicinski

skbuff: rewrite the doc for data-only skbs

2022-05-11T00:48:35+00:00

The comment about shinfo->dataref split is really unhelpful, at least to me. Rewrite it and render it to skb documentation. Reviewed-by: David Ahern Signed-off-by: Jakub Kicinski