| Message ID | e3a16eacdc6740658ee02a33489b1b9d4912f378.1719992715.git.tanggeliang@kylinos.cn (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | f0c18025693707ec344a70b6887f7450bf4c826b |
| Headers | show |
| Series | [net,v5] skmsg: skip zero length skb in sk_msg_recvmsg | expand |
Geliang Tang wrote: > From: Geliang Tang <tanggeliang@kylinos.cn> > > Run this BPF selftests (./test_progs -t sockmap_basic) on a Loongarch > platform, a kernel panic occurs: > > ''' > Oops[#1]: > CPU: 22 PID: 2824 Comm: test_progs Tainted: G OE 6.10.0-rc2+ #18 > Hardware name: LOONGSON Dabieshan/Loongson-TC542F0, BIOS Loongson-UDK2018 > ... ... > ra: 90000000048bf6c0 sk_msg_recvmsg+0x120/0x560 > ERA: 9000000004162774 copy_page_to_iter+0x74/0x1c0 > CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) > PRMD: 0000000c (PPLV0 +PIE +PWE) > EUEN: 00000007 (+FPE +SXE +ASXE -BTE) > ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7) > ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0) > BADV: 0000000000000040 > PRID: 0014c011 (Loongson-64bit, Loongson-3C5000) > Modules linked in: bpf_testmod(OE) xt_CHECKSUM xt_MASQUERADE xt_conntrack > Process test_progs (pid: 2824, threadinfo=0000000000863a31, task=...) > Stack : ... > ... > Call Trace: > [<9000000004162774>] copy_page_to_iter+0x74/0x1c0 > [<90000000048bf6c0>] sk_msg_recvmsg+0x120/0x560 > [<90000000049f2b90>] tcp_bpf_recvmsg_parser+0x170/0x4e0 > [<90000000049aae34>] inet_recvmsg+0x54/0x100 > [<900000000481ad5c>] sock_recvmsg+0x7c/0xe0 > [<900000000481e1a8>] __sys_recvfrom+0x108/0x1c0 > [<900000000481e27c>] sys_recvfrom+0x1c/0x40 > [<9000000004c076ec>] do_syscall+0x8c/0xc0 > [<9000000003731da4>] handle_syscall+0xc4/0x160 > > Code: ... > > ---[ end trace 0000000000000000 ]--- > Kernel panic - not syncing: Fatal exception > Kernel relocated by 0x3510000 > .text @ 0x9000000003710000 > .data @ 0x9000000004d70000 > .bss @ 0x9000000006469400 > ---[ end Kernel panic - not syncing: Fatal exception ]--- > ''' > > This crash happens every time when running sockmap_skb_verdict_shutdown > subtest in sockmap_basic. > > This crash is because a NULL pointer is passed to page_address() in > sk_msg_recvmsg(). Due to the difference implementations depending on the > architecture, page_address(NULL) will trigger a panic on Loongarch > platform but not on X86 platform. So this bug was hidden on X86 platform > for a while, but now it is exposed on Loongarch platform. > > The root cause is a zero length skb (skb->len == 0) is put on the queue. > > This zero length skb is a TCP FIN packet, which is sent by shutdown(), > invoked in test_sockmap_skb_verdict_shutdown(): > > shutdown(p1, SHUT_WR); > > In this case, in sk_psock_skb_ingress_enqueue(), num_sge is zero, and no > page is put to this sge (see sg_set_page in sg_set_page), but this empty > sge is queued into ingress_msg list. > > And in sk_msg_recvmsg(), this empty sge is used, and a NULL page is got by > sg_page(sge). Pass this NULL page to copy_page_to_iter(), which passes it > to kmap_local_page() and to page_address(), then kernel panics. > > To solve this, we should skip this zero length skb. So in sk_msg_recvmsg(), > if copy is zero, that means it's a zero length skb, skip invoking > copy_page_to_iter(). We are using the EFAULT return triggered by > copy_page_to_iter to check for is_fin in tcp_bpf.c. > > Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") > Suggested-by: John Fastabend <john.fastabend@gmail.com> > Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn> > --- > v5: > - update v5 as John suggested. > - skmsg: skip zero length skb in sk_msg_recvmsg > > v4: > - skmsg: skip empty sge in sk_msg_recvmsg > > v3: > - skmsg: prevent empty ingress skb from enqueuing > > v2: > - skmsg: null check for sg_page in sk_msg_recvmsg > --- > net/core/skmsg.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) I don't have any better ideas so lets use this. Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Hello: This patch was applied to bpf/bpf.git (master) by Daniel Borkmann <daniel@iogearbox.net>: On Wed, 3 Jul 2024 16:39:31 +0800 you wrote: > From: Geliang Tang <tanggeliang@kylinos.cn> > > Run this BPF selftests (./test_progs -t sockmap_basic) on a Loongarch > platform, a kernel panic occurs: > > ''' > Oops[#1]: > CPU: 22 PID: 2824 Comm: test_progs Tainted: G OE 6.10.0-rc2+ #18 > Hardware name: LOONGSON Dabieshan/Loongson-TC542F0, BIOS Loongson-UDK2018 > ... ... > ra: 90000000048bf6c0 sk_msg_recvmsg+0x120/0x560 > ERA: 9000000004162774 copy_page_to_iter+0x74/0x1c0 > CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) > PRMD: 0000000c (PPLV0 +PIE +PWE) > EUEN: 00000007 (+FPE +SXE +ASXE -BTE) > ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7) > ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0) > BADV: 0000000000000040 > PRID: 0014c011 (Loongson-64bit, Loongson-3C5000) > Modules linked in: bpf_testmod(OE) xt_CHECKSUM xt_MASQUERADE xt_conntrack > Process test_progs (pid: 2824, threadinfo=0000000000863a31, task=...) > Stack : ... > ... > Call Trace: > [<9000000004162774>] copy_page_to_iter+0x74/0x1c0 > [<90000000048bf6c0>] sk_msg_recvmsg+0x120/0x560 > [<90000000049f2b90>] tcp_bpf_recvmsg_parser+0x170/0x4e0 > [<90000000049aae34>] inet_recvmsg+0x54/0x100 > [<900000000481ad5c>] sock_recvmsg+0x7c/0xe0 > [<900000000481e1a8>] __sys_recvfrom+0x108/0x1c0 > [<900000000481e27c>] sys_recvfrom+0x1c/0x40 > [<9000000004c076ec>] do_syscall+0x8c/0xc0 > [<9000000003731da4>] handle_syscall+0xc4/0x160 > > [...] Here is the summary with links: - [net,v5] skmsg: skip zero length skb in sk_msg_recvmsg https://git.kernel.org/bpf/bpf/c/f0c180256937 You are awesome, thank you!
diff --git a/net/core/skmsg.c b/net/core/skmsg.c index fd20aae30be2..bbf40b999713 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -434,7 +434,8 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg, page = sg_page(sge); if (copied + copy > len) copy = len - copied; - copy = copy_page_to_iter(page, sge->offset, copy, iter); + if (copy) + copy = copy_page_to_iter(page, sge->offset, copy, iter); if (!copy) { copied = copied ? copied : -EFAULT; goto out;