From patchwork Wed Aug 7 23:40:22 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13756851 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B831F155337; Wed, 7 Aug 2024 23:40:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723074043; cv=none; b=m6PX5bV2hCn2+kz1FhpivVwe84hRemPKp6VqFYooIpfWd6SY++RCQpYEWYiFHmaFDYYgqOty5+jzxXWwQcI77DjFtsWQI+mmUWTrY/hDyuUWStqF/QqblkNOMKmt8vqwBSS3/ZLn+T2PVUrM5kNdflIC1wwg1MN+6md/PW+5UvU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723074043; c=relaxed/simple; bh=p0Hrh9D8jfWPnv3wRuqHv+z7HSONG3+t+yQ8X6UTtgk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ElUcU2y2Yjeo1owglrNeQGUAu2divj+TWGWjezFntjHmjTlY8a3+JWG6X5ow/ZTF8972fDi8EbnCCj2Bvu7dDcAFFn8+H/U+d4ztYcuzPuo2hngGYEJzwC11dZ/N0FROn/zVxg2uDqTlTjrfluyEJvU37y4PPL3bDH1akRV8ANE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QfRxHav2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QfRxHav2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1A40EC32781; Wed, 7 Aug 2024 23:40:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723074043; bh=p0Hrh9D8jfWPnv3wRuqHv+z7HSONG3+t+yQ8X6UTtgk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QfRxHav2I85dVDDJN63ZgXQ7nwgkQ9cZLs5WETdCaEYU55dh6HCLvroeJaJURWQ3q 6Ikc7F7Kij+g3EJxsxX2/qtS97KEN0rpKR/JtbqX7zgMGAZOyYECbOHYfVun3zvvUK oLv+nEi5BQ4LwFQnJ//je5+/3gwqDorhgsGSJQruFX60891dVCjMLqagfXxTU+2WLk GHWceKnOz8s0djK0yUW35pdoumGVlQiNwKSuLsVVrf9EGWmvuQ7wHp+4KfTxAq5A8k 3qKprgPxepGsbb3J2TFmT8kqmB/uvNhmQV8XA3ucMt2zWh8KuSUcK5PPu4Wd2T36Gh HiLGsp2tNp9gw== From: Andrii Nakryiko To: bpf@vger.kernel.org Cc: linux-mm@kvack.org, akpm@linux-foundation.org, adobriyan@gmail.com, shakeel.butt@linux.dev, hannes@cmpxchg.org, ak@linux.intel.com, osandov@osandov.com, song@kernel.org, jannh@google.com, linux-fsdevel@vger.kernel.org, willy@infradead.org, Andrii Nakryiko Subject: [PATCH v4 bpf-next 03/10] lib/buildid: take into account e_phoff when fetching program headers Date: Wed, 7 Aug 2024 16:40:22 -0700 Message-ID: <20240807234029.456316-4-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20240807234029.456316-1-andrii@kernel.org> References: <20240807234029.456316-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Current code assumption is that program (segment) headers are following ELF header immediately. This is a common case, but is not guaranteed. So take into account e_phoff field of the ELF header when accessing program headers. Reported-by: Alexey Dobriyan Signed-off-by: Andrii Nakryiko --- lib/buildid.c | 35 ++++++++++++++++------------------- 1 file changed, 16 insertions(+), 19 deletions(-) diff --git a/lib/buildid.c b/lib/buildid.c index f5ffc3d9f786..0183f5ece75b 100644 --- a/lib/buildid.c +++ b/lib/buildid.c @@ -210,28 +210,26 @@ static int get_build_id_32(struct freader *r, unsigned char *build_id, __u32 *si { const Elf32_Ehdr *ehdr; const Elf32_Phdr *phdr; - __u32 phnum, i; + __u32 phnum, phoff, i; ehdr = freader_fetch(r, 0, sizeof(Elf32_Ehdr)); if (!ehdr) return r->err; - /* - * FIXME - * Neither ELF spec nor ELF loader require that program headers - * start immediately after ELF header. - */ - if (ehdr->e_phoff != sizeof(Elf32_Ehdr)) - return -EINVAL; - /* subsequent freader_fetch() calls invalidate pointers, so remember locally */ phnum = READ_ONCE(ehdr->e_phnum); + phoff = READ_ONCE(ehdr->e_phoff); + /* only supports phdr that fits in one page */ if (phnum > (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr)) return -EINVAL; + /* check that phoff is not large enough to cause an overflow */ + if (phoff + phnum * sizeof(Elf32_Phdr) < phoff) + return -EINVAL; + for (i = 0; i < phnum; ++i) { - phdr = freader_fetch(r, i * sizeof(Elf32_Phdr), sizeof(Elf32_Phdr)); + phdr = freader_fetch(r, phoff + i * sizeof(Elf32_Phdr), sizeof(Elf32_Phdr)); if (!phdr) return r->err; @@ -249,27 +247,26 @@ static int get_build_id_64(struct freader *r, unsigned char *build_id, __u32 *si const Elf64_Ehdr *ehdr; const Elf64_Phdr *phdr; __u32 phnum, i; + __u64 phoff; ehdr = freader_fetch(r, 0, sizeof(Elf64_Ehdr)); if (!ehdr) return r->err; - /* - * FIXME - * Neither ELF spec nor ELF loader require that program headers - * start immediately after ELF header. - */ - if (ehdr->e_phoff != sizeof(Elf64_Ehdr)) - return -EINVAL; - /* subsequent freader_fetch() calls invalidate pointers, so remember locally */ phnum = READ_ONCE(ehdr->e_phnum); + phoff = READ_ONCE(ehdr->e_phoff); + /* only supports phdr that fits in one page */ if (phnum > (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr)) return -EINVAL; + /* check that phoff is not large enough to cause an overflow */ + if (phoff + phnum * sizeof(Elf64_Phdr) < phoff) + return -EINVAL; + for (i = 0; i < phnum; ++i) { - phdr = freader_fetch(r, i * sizeof(Elf64_Phdr), sizeof(Elf64_Phdr)); + phdr = freader_fetch(r, phoff + i * sizeof(Elf64_Phdr), sizeof(Elf64_Phdr)); if (!phdr) return r->err;