From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 146B16B0038 for ; Tue, 20 Sep 2016 19:01:46 -0400 (EDT) Received: by mail-lf0-f69.google.com with SMTP id n4so26012183lfb.3 for ; Tue, 20 Sep 2016 16:01:46 -0700 (PDT) Received: from mail-wm0-x22e.google.com (mail-wm0-x22e.google.com. [2a00:1450:400c:c09::22e]) by mx.google.com with ESMTPS id 66si5521387wmy.42.2016.09.20.16.01.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Sep 2016 16:01:44 -0700 (PDT) Received: by mail-wm0-x22e.google.com with SMTP id l132so60535252wmf.1 for ; Tue, 20 Sep 2016 16:01:44 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1474386996-16049-1-git-send-email-labbott@redhat.com> References: <1474386996-16049-1-git-send-email-labbott@redhat.com> From: Kees Cook Date: Tue, 20 Sep 2016 16:01:43 -0700 Message-ID: Subject: Re: [PATCH] mm: usercopy: Check for module addresses Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Laura Abbott Cc: Linux-MM , LKML , "kernel-hardening@lists.openwall.com" On Tue, Sep 20, 2016 at 8:56 AM, Laura Abbott wrote: > While running a compile on arm64, I hit a memory exposure > > usercopy: kernel memory exposure attempt detected from fffffc0000f3b1a8 (buffer_head) (1 bytes) > ------------[ cut here ]------------ > kernel BUG at mm/usercopy.c:75! > Internal error: Oops - BUG: 0 [#1] SMP > Modules linked in: ip6t_rpfilter ip6t_REJECT > nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_broute bridge stp > llc ebtable_nat ip6table_security ip6table_raw ip6table_nat > nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle > iptable_security iptable_raw iptable_nat nf_conntrack_ipv4 > nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle > ebtable_filter ebtables ip6table_filter ip6_tables vfat fat xgene_edac > xgene_enet edac_core i2c_xgene_slimpro i2c_core at803x realtek xgene_dma > mdio_xgene gpio_dwapb gpio_xgene_sb xgene_rng mailbox_xgene_slimpro nfsd > auth_rpcgss nfs_acl lockd grace sunrpc xfs libcrc32c sdhci_of_arasan > sdhci_pltfm sdhci mmc_core xhci_plat_hcd gpio_keys > CPU: 0 PID: 19744 Comm: updatedb Tainted: G W 4.8.0-rc3-threadinfo+ #1 > Hardware name: AppliedMicro X-Gene Mustang Board/X-Gene Mustang Board, BIOS 3.06.12 Aug 12 2016 > task: fffffe03df944c00 task.stack: fffffe00d128c000 > PC is at __check_object_size+0x70/0x3f0 > LR is at __check_object_size+0x70/0x3f0 > ... > [] __check_object_size+0x70/0x3f0 > [] filldir64+0x158/0x1a0 > [] __fat_readdir+0x4a0/0x558 [fat] > [] fat_readdir+0x34/0x40 [fat] > [] iterate_dir+0x190/0x1e0 > [] SyS_getdents64+0x88/0x120 > [] el0_svc_naked+0x24/0x28 > > fffffc0000f3b1a8 is a module address. Modules may have compiled in > strings which could get copied to userspace. In this instance, it > looks like "." which matches with a size of 1 byte. Extend the > is_vmalloc_addr check to be is_vmalloc_or_module_addr to cover > all possible cases. > > Signed-off-by: Laura Abbott > --- > Longer term, it would be good to expand the check for to regions like > regular kernel memory. > --- > mm/usercopy.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/usercopy.c b/mm/usercopy.c > index 8ebae91..d8b5bd3 100644 > --- a/mm/usercopy.c > +++ b/mm/usercopy.c > @@ -145,8 +145,11 @@ static inline const char *check_heap_object(const void *ptr, unsigned long n, > * Some architectures (arm64) return true for virt_addr_valid() on > * vmalloced addresses. Work around this by checking for vmalloc > * first. > + * > + * We also need to check for module addresses explicitly since we > + * may copy static data from modules to userspace > */ > - if (is_vmalloc_addr(ptr)) > + if (is_vmalloc_or_module_addr(ptr)) > return NULL; I still don't understand why this happens on arm64 and not x86. (Really what I don't understand is what virt_addr_valid() is actually checking -- they seem to be checking very different things between x86 and arm64.) Regardless, I'll get this pushed to Linus and try to make the -rc8 cut. Thanks! -Kees > > if (!virt_addr_valid(ptr)) > -- > 2.7.4 > -- Kees Cook Nexus Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org