From patchwork Thu Jul 25 00:32:50 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Leon Hwang X-Patchwork-Id: 13741479 X-Patchwork-Delegate: bpf@iogearbox.net Received: from out-172.mta0.migadu.com (out-172.mta0.migadu.com [91.218.175.172]) (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 15CE123CB for ; Thu, 25 Jul 2024 00:33:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721867595; cv=none; b=PreImbceFTkdGJqrSkN3P5KDjkqRapdCVnaavA9/MjJgodUPLhhrqiQEn98ZTnHOU6anMtcVXNRLuubX03TSSrKYVYqyr6eu4++CttezTUYeaI1lMmTEEzytlK1xpNrDISFwjWfwmfjhuWLYUPWMUPvDStd62cyWdgZ+GvFY9r8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721867595; c=relaxed/simple; bh=ZtLiyxSKMb5P4riIoAMXhNKy3CtATILLYQLu02n68MY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=kve+5xrjFeypbFdEeR/3BLkBMU7FcdO/x/YPSY2QY1KMxf4t8r9oYupGpO4Ow2QwtTk3RA9V37YYL1EhPbTqgveMWB/QWKjGh7oWYhfYs03GS8udk1bhKZmLyU0IQsAQWj7NvPl/zwFOqPiLCfcWZOfssAlPDVHZedwfLi0mcHg= 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=nUkgrEYD; arc=none smtp.client-ip=91.218.175.172 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="nUkgrEYD" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1721867590; 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=+ZYRxJYlTl5TcpclwDh+0QBzN9UK/ckcG5I/pF9JewU=; b=nUkgrEYDP/yc/TLFbdbyvjDqRYKcgpdUlPflr8Gz710gTU9uAlT6GGvuIIAcFBjvmimQww 5INNZ1p3G7btIDqcG95NoJaCmLfj2COFCRI4zn0jBM0cLhC5YdbeuhWsn3U6fx2PniCiAc nfTMWM01Q6DEQ00xAY2gRB1XCk/LCe0= From: Leon Hwang To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, toke@redhat.com, martin.lau@kernel.org, eddyz87@gmail.com, yonghong.song@linux.dev, wutengda@huaweicloud.com, leon.hwang@linux.dev, kernel-patches-bot@fb.com Subject: [PATCH bpf-next 1/2] bpf: Fix updating attached freplace prog to PROG_ARRAY map Date: Thu, 25 Jul 2024 08:32:50 +0800 Message-ID: <20240725003251.37855-2-leon.hwang@linux.dev> In-Reply-To: <20240725003251.37855-1-leon.hwang@linux.dev> References: <20240725003251.37855-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net 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. But, it does not support updating attached freplace prog to PROG_ARRAY map. [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 Since commit 1c123c567fb138eb ("bpf: Resolve fext program type when checking map compatibility"), freplace prog can be used as tail-callee of its target 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. 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; } 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; } static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)