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 879E75221F4; Wed, 30 Sep 2026 18:25:49 +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=1790792750; cv=none; b=fUstbaHOLnio2SWIMyobxHIFsmAbqk5Bw6afuK6YNiyRhXNWGrGipV6cHzwsK26TelzJsWtr5fKfeLJhG3rrYzvxSCaGUl1PKa7mfpQIYAKBFqHRcNMvDDK/pQxZsNUrk6LdqBTNl+pypF1GLEGG5SyO+UZ6jIeV+qqn5BCDLe8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790792750; c=relaxed/simple; bh=so7pRcfnmG8vFTQtrXnAOTRc43CGCEB8b5kfYDP/VMQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NOqPfA8nPqmN4kJp2R4eGDNcLCOqW6pJbtLQynLTWqGxlLddzDMLSEjgXYpIduLOkvdzvOc55H6khtrVUeSHpJaRp8vGkioEp577qHXvnVnHo6Wa3UBjCY/UYtUuAxEgX3d4fM0V/cONNBhS/9vMV3ZvjmvD5YQZGBZnlziSP0U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=oEW/HoWA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="oEW/HoWA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0B961F000FF; Wed, 30 Sep 2026 18:25:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790792749; bh=p5ZICDrVah19xtNRDq0drX3yOIwDYQgpii+2tAfBtSE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=oEW/HoWAcOfXcuqapzMa9dGCaGpZS8tCDXXrHNQFFmaSajEDZfpEAMZ6HZTgiA+mJ JTYranUmJpq+r0ZIyVZIfwJ2Rdqe9WHXQ/IrhYmpPkcUh6TL5iRP1iQjbS3QWcnI5N rzuVxajrad3nRqUo6/Q1dqCmn/8cOiuPkCxI07hY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jiayuan Chen , Eduard Zingerman , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.18 013/395] bpf: Fix divide-by-zero in btf_struct_walk() Date: Wed, 30 Sep 2026 17:24:35 +0200 Message-ID: <20260930152340.904238781@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152340.591469096@linuxfoundation.org> References: <20260930152340.591469096@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen [ Upstream commit b0b3dc66529676228cb938cbcad66920f735c223 ] When an access goes past the struct and the last member is a flexible array, btf_struct_walk() folds the offset back into a single element with (off - moff) % t->size, but never checks that the element type has a size. BTF takes an empty struct, so this in program BTF /* event could be empty */ struct event { #ifdef HAVE_TIMESTAMP __u64 ts; #endif }; struct batch { int nr; struct event events[]; }; divides by zero at prog load time. Getting there needs a PTR_TO_BTF_ID that is not MEM_ALLOC, e.g. a plain read of a local kptr stashed in a map from a sleepable program. Oops: divide error: 0000 [#1] SMP KASAN PTI RIP: 0010:btf_struct_walk+0x53f/0x1570 Call Trace: btf_struct_access+0x42a/0xcd0 check_ptr_to_btf_access+0x4dc/0x1160 check_mem_access+0x3a45/0x8740 check_load_mem+0x36a/0xd10 do_check_common+0x3ef0/0xb210 bpf_check+0x6d3b/0x8580 bpf_prog_load+0xf7c/0x2720 __sys_bpf+0xa83/0x3690 __x64_sys_bpf+0xc7/0x150 x64_sys_call+0x1f3f/0x27e0 do_syscall_64+0xe5/0x610 entry_SYSCALL_64_after_hwframe+0x76/0x7e Reject a zero-sized element type. The fixed array path in the same function already bails out on the same thing: btf_struct_walk() ... /* skip empty array */ if (moff == mtrue_end) continue; msize /= total_nelems; Fixes: 9c5f8a1008a1 ("bpf: Support variable length array in tracing programs") Signed-off-by: Jiayuan Chen Acked-by: Eduard Zingerman Link: https://lore.kernel.org/r/20260910122316.186384-1-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/btf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index f92e1c16c3569..86a4f76e79403 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -7004,7 +7004,7 @@ static int btf_struct_walk(struct bpf_verifier_log *log, const struct btf *btf, if (btf_type_is_int(t)) return WALK_SCALAR; - if (!btf_type_is_struct(t)) + if (!btf_type_is_struct(t) || !t->size) goto error; off = (off - moff) % t->size; -- 2.53.0