From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F00A458222 for ; Thu, 25 Jul 2024 20:58:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721941105; cv=none; b=iH+zOc9QySYbmsFb95S4U4YhlrpJTYvgK+LoLt7tLf0caSQGkxTJ7EfGxJoCA+sW+E5R2cNgAgNuPbHqNQT/4f6821KAqYJhk1Nj20N4XQLziUe5Y5tWBtVAfbo9iR5bjmXFLaLwltZnLf0Cg16p1dhNM7ov39vizrteMkR551w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721941105; c=relaxed/simple; bh=ITnDSYcU1nq0rMq15OJhAYqdkpW5wsxm2a5qiZYqbsY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mI+xlLsJwifCMe5/GpaB33iUn6Zi9Huc32gE1DxxKXI+DYmwhIpekkU8mK1yguj9yCGuZRfBebQ01obbnO2ybGgeBCmLkpEl3KJL+uqIhDWkpPR1/3RaxkMkALK1s7WnTxbbNtg+rVjDpoDFHD+nTsNPmBRXGFLtaaEhKU9kjGY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=MpgLJDGd; arc=none smtp.client-ip=95.215.58.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="MpgLJDGd" Message-ID: <181a9753-717c-4eb4-b788-74468f68c0ff@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1721941100; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lQqyhPBtaPJcsgGATt/tcTKERtDG9BTey0YKW6HJzfg=; b=MpgLJDGd2Ij7W+St5ktRQ+1rKqWgGJyxXhfiq4rfr8bK7iidYRIpi4QZTeknf7SxmkQVhU CZxPrAoHTxqyyiCpKl8h3WYI3CRPhaClwwXY03OfAjE17jdKsaR6+Vs+4ygvtsf1RKt1rl 6HA7f0SIT8wLUKnw69rlx/FXK7fORbA= Date: Thu, 25 Jul 2024 13:58:12 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next 1/2] bpf: Fix updating attached freplace prog to PROG_ARRAY map To: Leon Hwang , bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, toke@redhat.com, martin.lau@kernel.org, eddyz87@gmail.com, wutengda@huaweicloud.com, kernel-patches-bot@fb.com References: <20240725003251.37855-1-leon.hwang@linux.dev> <20240725003251.37855-2-leon.hwang@linux.dev> Content-Language: en-GB X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <20240725003251.37855-2-leon.hwang@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 7/24/24 5:32 PM, Leon Hwang wrote: > The commit f7866c3587337731 ("bpf: Fix null pointer dereference in > resolve_prog_type() for BPF_PROG_TYPE_EXT") fixed the following panic, > which was caused by updating attached freplace prog to PROG_ARRAY map. I am confused here. You mentioned that commit f7866c3587337731 fixed the panic below. But looking at commit message: https://lore.kernel.org/bpf/20240711145819.254178-2-wutengda@huaweicloud.com it does not seem the case. > > But, it does not support updating attached freplace prog to PROG_ARRAY > map. This seems true since this patch itself intends fixing this issue. > > [309049.036402] BUG: kernel NULL pointer dereference, address: 0000000000000004 > [309049.036419] #PF: supervisor read access in kernel mode > [309049.036426] #PF: error_code(0x0000) - not-present page > [309049.036432] PGD 0 P4D 0 > [309049.036437] Oops: 0000 [#1] PREEMPT SMP NOPTI > [309049.036444] CPU: 2 PID: 788148 Comm: test_progs Not tainted 6.8.0-31-generic #31-Ubuntu > [309049.036465] Hardware name: VMware, Inc. VMware20,1/440BX Desktop Reference Platform, BIOS VMW201.00V.21805430.B64.2305221830 05/22/2023 > [309049.036477] RIP: 0010:bpf_prog_map_compatible+0x2a/0x140 > [309049.036488] Code: 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 49 89 fe 41 55 41 54 53 44 8b 6e 04 48 89 f3 41 83 fd 1c 75 0c 48 8b 46 38 48 8b 40 70 <44> 8b 68 04 f6 43 03 01 75 1c 48 8b 43 38 44 0f b6 a0 89 00 00 00 > [309049.036505] RSP: 0018:ffffb2e080fd7ce0 EFLAGS: 00010246 > [309049.036513] RAX: 0000000000000000 RBX: ffffb2e0807c1000 RCX: 0000000000000000 > [309049.036521] RDX: 0000000000000000 RSI: ffffb2e0807c1000 RDI: ffff990290259e00 > [309049.036528] RBP: ffffb2e080fd7d08 R08: 0000000000000000 R09: 0000000000000000 > [309049.036536] R10: 0000000000000000 R11: 0000000000000000 R12: ffff990290259e00 > [309049.036543] R13: 000000000000001c R14: ffff990290259e00 R15: ffff99028e29c400 > [309049.036551] FS: 00007b82cbc28140(0000) GS:ffff9903b3f00000(0000) knlGS:0000000000000000 > [309049.036559] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [309049.036566] CR2: 0000000000000004 CR3: 0000000101286002 CR4: 00000000003706f0 > [309049.036573] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [309049.036581] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [309049.036588] Call Trace: > [309049.036592] > [309049.036597] ? show_regs+0x6d/0x80 > [309049.036604] ? __die+0x24/0x80 > [309049.036619] ? page_fault_oops+0x99/0x1b0 > [309049.036628] ? do_user_addr_fault+0x2ee/0x6b0 > [309049.036634] ? exc_page_fault+0x83/0x1b0 > [309049.036641] ? asm_exc_page_fault+0x27/0x30 > [309049.036649] ? bpf_prog_map_compatible+0x2a/0x140 > [309049.036656] prog_fd_array_get_ptr+0x2c/0x70 > [309049.036664] bpf_fd_array_map_update_elem+0x37/0x130 > [309049.036671] bpf_map_update_value+0x1d3/0x260 > [309049.036677] map_update_elem+0x1fa/0x360 > [309049.036683] __sys_bpf+0x54c/0xa10 > [309049.036689] __x64_sys_bpf+0x1a/0x30 > [309049.036694] x64_sys_call+0x1936/0x25c0 > [309049.036700] do_syscall_64+0x7f/0x180 > [309049.036706] ? do_syscall_64+0x8c/0x180 > [309049.036712] ? do_syscall_64+0x8c/0x180 > [309049.036717] ? irqentry_exit+0x43/0x50 > [309049.036723] ? common_interrupt+0x54/0xb0 > [309049.036729] entry_SYSCALL_64_after_hwframe+0x73/0x7b I actually tried your selftest (patch 2/2) without patch 1/1, I got the following error: All error logs: tester_init:PASS:tester_log_buf 0 nsec process_subtest:PASS:obj_open_mem 0 nsec process_subtest:PASS:specs_alloc 0 nsec test_tailcall_freplace:PASS:open fr_skel 0 nsec test_tailcall_freplace:PASS:open tc_skel 0 nsec test_tailcall_freplace:PASS:tc_skel entry prog_id 0 nsec test_tailcall_freplace:PASS:set_attach_target 0 nsec test_tailcall_freplace:PASS:load fr_skel 0 nsec test_tailcall_freplace:PASS:attach_freplace 0 nsec test_tailcall_freplace:PASS:fr_skel entry prog_fd 0 nsec test_tailcall_freplace:PASS:fr_skel jmp_table map_fd 0 nsec test_tailcall_freplace:FAIL:update jmp_table unexpected error: -22 (errno 22) #328/25 tailcalls/tailcall_freplace:FAIL #328 tailcalls:FAIL I didn't see kernel panic. > > Since commit 1c123c567fb138eb ("bpf: Resolve fext program type when > checking map compatibility"), freplace prog can be used as tail-callee > of its target prog. the tailcall target can be a freplace prog. > And the commit 3aac1ead5eb6b76f ("bpf: Move prog->aux->linked_prog and > trampoline into bpf_link on attach") sets prog->aux->dst_prog as NULL > when attach freplace prog to its target. when attach -> after attaching > > Then, as for following example: > > tailcall_freplace.c: > > // SPDX-License-Identifier: GPL-2.0 > > \#include > \#include > \#include "bpf_legacy.h" > > struct { > __uint(type, BPF_MAP_TYPE_PROG_ARRAY); > __uint(max_entries, 1); > __uint(key_size, sizeof(__u32)); > __uint(value_size, sizeof(__u32)); > } jmp_table SEC(".maps"); > > int count = 0; > > __noinline int > subprog(struct __sk_buff *skb) > { > volatile int ret = 1; > > count++; > > bpf_tail_call_static(skb, &jmp_table, 0); > > return ret; > } This subprog is not needed and could be misleading, just inline subprog into entry prog, it should be okay. > > SEC("freplace") > int entry(struct __sk_buff *skb) > { > return subprog(skb); > } > > char __license[] SEC("license") = "GPL"; > > tc_bpf2bpf.c: > > // SPDX-License-Identifier: GPL-2.0 > > \#include > \#include > \#include "bpf_legacy.h" > > __noinline int > subprog(struct __sk_buff *skb) > { > volatile int ret = 1; > > return ret; > } > > SEC("tc") > int entry(struct __sk_buff *skb) > { > return subprog(skb); > } > > char __license[] SEC("license") = "GPL"; > > And freplace entry prog's target is the tc subprog. > > After loading, the freplace jmp_table's owner type is > BPF_PROG_TYPE_SCHED_CLS. > > Next, after attaching freplace prog to tc subprog, its prog->aux-> > dst_prog is NULL. > > Next, when update freplace prog to jmp_table, bpf_prog_map_compatible() > returns false because resolve_prog_type() returns BPF_PROG_TYPE_EXT instead > of BPF_PROG_TYPE_SCHED_CLS. > > With this patch, resolve_prog_type() returns BPF_PROG_TYPE_SCHED_CLS to > support updating attached freplace prog to PROG_ARRY map for this > example. > > Fixes: f7866c358733 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT") > Cc: Toke Høiland-Jørgensen > Cc: Martin KaFai Lau > Signed-off-by: Leon Hwang > --- > include/linux/bpf_verifier.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h > index 5cea15c81b8a8..387e034e73d0e 100644 > --- a/include/linux/bpf_verifier.h > +++ b/include/linux/bpf_verifier.h > @@ -874,8 +874,8 @@ static inline u32 type_flag(u32 type) > /* only use after check_attach_btf_id() */ > static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog) > { > - return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->dst_prog) ? > - prog->aux->dst_prog->type : prog->type; > + return prog->type == BPF_PROG_TYPE_EXT ? > + prog->aux->saved_dst_prog_type : prog->type; If prog->aux->dst_prog is NULL, is it possible that prog->aux->saved_dst_prog_type (0, corresponding to BPF_PROG_TYPE_UNSPEC) could be returned? Do we need to do return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->saved_dst_prog_type) ? prog->aux->saved_dst_prog_type : prog->type; Maybe I missed something here? > } > > static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)