From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6E7CB558202 for ; Tue, 8 Sep 2026 13:32:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788874389; cv=none; b=AJN9zzQ8eBtFFldnlMlNWac7DSpiJ7nL0JSNfhmd/0PC2ckGCrfk0kb5arJOwu4xz/XCnkSLMidUBWBqR65ayPWrV5/JlvvDzA3Z1ZZw/RirGbeJY4MWVBSGnk9h03dCyTMhK8nwNDndxvwt8S5FJ26rq6vmhsQ+JTHfZsDargc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788874389; c=relaxed/simple; bh=myKcD2FsElqBvhWFDj6XfIomnq5GPYgPry5AtjUvCuI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u1VissceQn+RKo8AFk9Pxg2TUKfaRS7islyACrawv3aE+dW9HKR3J8csbnP9DPyfB3svcmNHV4gr23hWLvPY2TDWHIRabsPLsTp583SBPQfynsn90c71zOwppX/JGTd0ZyUNCcibMOtqHrZL0J30uZAUCk0SXiXUhilTUbayK6k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74F191F01558; Tue, 8 Sep 2026 13:32:54 +0000 (UTC) From: Sasha Levin To: stable@vger.kernel.org Cc: Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.6.y 2/3] bpf: decouple stack_map_get_build_id_offset() from perf_callchain_entry Date: Tue, 8 Sep 2026 09:32:50 -0400 Message-ID: <20260908133251.2324526-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260908133251.2324526-1-sashal@kernel.org> References: <2026090326-saturate-wobbling-7457@gregkh> <20260908133251.2324526-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Andrii Nakryiko [ Upstream commit 4f4c4fc0153fb11ac40b16c24a24543dc9689d8c ] Change stack_map_get_build_id_offset() which is used to convert stack trace IP addresses into build ID+offset pairs. Right now this function accepts an array of u64s as an input, and uses array of struct bpf_stack_build_id as an output. This is problematic because u64 array is coming from perf_callchain_entry, which is (non-sleepable) RCU protected, so once we allows sleepable build ID fetching, this all breaks down. But its actually pretty easy to make stack_map_get_build_id_offset() works with array of struct bpf_stack_build_id as both input and output. Which is what this patch is doing, eliminating the dependency on perf_callchain_entry. We require caller to fill out bpf_stack_build_id.ip fields (all other can be left uninitialized), and update in place as we do build ID resolution. We make sure to READ_ONCE() and cache locally current IP value as we used it in a few places to find matching VMA and so on. Given this data is directly accessible and modifiable by user's BPF code, we should make sure to have a consistent view of it. Reviewed-by: Eduard Zingerman Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20240829174232.3133883-9-andrii@kernel.org Signed-off-by: Alexei Starovoitov Stable-dep-of: b1a47b2708d4 ("bpf: Disable preemption in __bpf_get_stack") Signed-off-by: Sasha Levin --- kernel/bpf/stackmap.c | 49 +++++++++++++++++++++++++++++-------------- 1 file changed, 33 insertions(+), 16 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 0ed48217b2089..fac13cfb32eec 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -124,8 +124,18 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr) return ERR_PTR(err); } +/* + * Expects all id_offs[i].ip values to be set to correct initial IPs. + * They will be subsequently: + * - either adjusted in place to a file offset, if build ID fetching + * succeeds; in this case id_offs[i].build_id is set to correct build ID, + * and id_offs[i].status is set to BPF_STACK_BUILD_ID_VALID; + * - or IP will be kept intact, if build ID fetching failed; in this case + * id_offs[i].build_id is zeroed out and id_offs[i].status is set to + * BPF_STACK_BUILD_ID_IP. + */ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, - u64 *ips, u32 trace_nr, bool user) + u32 trace_nr, bool user) { int i; struct mmap_unlock_irq_work *work = NULL; @@ -142,30 +152,28 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, /* cannot access current->mm, fall back to ips */ for (i = 0; i < trace_nr; i++) { id_offs[i].status = BPF_STACK_BUILD_ID_IP; - id_offs[i].ip = ips[i]; memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX); } return; } for (i = 0; i < trace_nr; i++) { - if (range_in_vma(prev_vma, ips[i], ips[i])) { + u64 ip = READ_ONCE(id_offs[i].ip); + + if (range_in_vma(prev_vma, ip, ip)) { vma = prev_vma; - memcpy(id_offs[i].build_id, prev_build_id, - BUILD_ID_SIZE_MAX); + memcpy(id_offs[i].build_id, prev_build_id, BUILD_ID_SIZE_MAX); goto build_id_valid; } - vma = find_vma(current->mm, ips[i]); + vma = find_vma(current->mm, ip); if (!vma || build_id_parse_nofault(vma, id_offs[i].build_id, NULL)) { /* per entry fall back to ips */ id_offs[i].status = BPF_STACK_BUILD_ID_IP; - id_offs[i].ip = ips[i]; memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX); continue; } build_id_valid: - id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i] - - vma->vm_start; + id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ip - vma->vm_start; id_offs[i].status = BPF_STACK_BUILD_ID_VALID; prev_vma = vma; prev_build_id = id_offs[i].build_id; @@ -216,7 +224,7 @@ static long __bpf_get_stackid(struct bpf_map *map, struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); struct stack_map_bucket *bucket, *new_bucket, *old_bucket; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; - u32 hash, id, trace_nr, trace_len; + u32 hash, id, trace_nr, trace_len, i; bool user = flags & BPF_F_USER_STACK; u64 *ips; bool hash_matches; @@ -238,15 +246,18 @@ static long __bpf_get_stackid(struct bpf_map *map, return id; if (stack_map_use_build_id(map)) { + struct bpf_stack_build_id *id_offs; + /* for build_id+offset, pop a bucket before slow cmp */ new_bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) return -ENOMEM; new_bucket->nr = trace_nr; - stack_map_get_build_id_offset( - (struct bpf_stack_build_id *)new_bucket->data, - ips, trace_nr, user); + id_offs = (struct bpf_stack_build_id *)new_bucket->data; + for (i = 0; i < trace_nr; i++) + id_offs[i].ip = ips[i]; + stack_map_get_build_id_offset(id_offs, trace_nr, user); trace_len = trace_nr * sizeof(struct bpf_stack_build_id); if (hash_matches && bucket->nr == trace_nr && memcmp(bucket->data, new_bucket->data, trace_len) == 0) { @@ -445,10 +456,16 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, copy_len = trace_nr * elem_size; ips = trace->ip + skip; - if (user && user_build_id) - stack_map_get_build_id_offset(buf, ips, trace_nr, user); - else + if (user && user_build_id) { + struct bpf_stack_build_id *id_offs = buf; + u32 i; + + for (i = 0; i < trace_nr; i++) + id_offs[i].ip = ips[i]; + stack_map_get_build_id_offset(buf, trace_nr, user); + } else { memcpy(buf, ips, copy_len); + } if (size > copy_len) memset(buf + copy_len, 0, size - copy_len); -- 2.53.0