| Message ID | 334d4b64cf1adb8fe65ae4581d01b9698d5e23b1.1520258376.git.pabeni@redhat.com |
|---|---|
| State | Not Applicable |
| Delegated to: | Pablo Neira |
| Headers | show |
| Series | [net] netfilter: check for out-of-bounds while copying compat entries | expand |
Paolo Abeni <pabeni@redhat.com> wrote: > Currently, when coping ebt compat entries, no checks are in place > for the offsets provided by user space, so that syzbot was able to > trigger the following splat: > --- > net/bridge/netfilter/ebtables.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c > index 02c4b409d317..54ceaff701fb 100644 > --- a/net/bridge/netfilter/ebtables.c > +++ b/net/bridge/netfilter/ebtables.c > @@ -2114,7 +2114,7 @@ static int size_entry_mwt(struct ebt_entry *entry, const unsigned char *base, > unsigned int size; > char *buf = buf_start + offsets[i]; > > - if (offsets[i] > offsets[j]) > + if (offsets[i] > offsets[j] || offsets[j] > *total) > return -EINVAL; I thought i fixed this via b71812168571fa55e44cdd0254471331b9c4c4c6, and, after looking at it again I still don't see why that doesn't cover this :-( -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 2018-03-05 at 15:32 +0100, Florian Westphal wrote: > Paolo Abeni <pabeni@redhat.com> wrote: > > Currently, when coping ebt compat entries, no checks are in place > > for the offsets provided by user space, so that syzbot was able to > > trigger the following splat: > > --- > > net/bridge/netfilter/ebtables.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c > > index 02c4b409d317..54ceaff701fb 100644 > > --- a/net/bridge/netfilter/ebtables.c > > +++ b/net/bridge/netfilter/ebtables.c > > @@ -2114,7 +2114,7 @@ static int size_entry_mwt(struct ebt_entry *entry, const unsigned char *base, > > unsigned int size; > > char *buf = buf_start + offsets[i]; > > > > - if (offsets[i] > offsets[j]) > > + if (offsets[i] > offsets[j] || offsets[j] > *total) > > return -EINVAL; > > I thought i fixed this via b71812168571fa55e44cdd0254471331b9c4c4c6, > and, after looking at it again I still don't see why that doesn't cover > this :-( Actually such commit fixes the issues (I just double-checked via syzbot), the issue is I did not pull such changeset before starting investigating this bug. This patch is not needed, thanks. Paolo -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c index 02c4b409d317..54ceaff701fb 100644 --- a/net/bridge/netfilter/ebtables.c +++ b/net/bridge/netfilter/ebtables.c @@ -2114,7 +2114,7 @@ static int size_entry_mwt(struct ebt_entry *entry, const unsigned char *base, unsigned int size; char *buf = buf_start + offsets[i]; - if (offsets[i] > offsets[j]) + if (offsets[i] > offsets[j] || offsets[j] > *total) return -EINVAL; match32 = (struct compat_ebt_entry_mwt *) buf;
Currently, when coping ebt compat entries, no checks are in place for the offsets provided by user space, so that syzbot was able to trigger the following splat: BUG: unable to handle kernel paging request at ffffc90001819e4f IP: ebt_size_mwt net/bridge/netfilter/ebtables.c:2037 [inline] IP: size_entry_mwt net/bridge/netfilter/ebtables.c:2122 [inline] IP: compat_copy_entries+0x49f/0x1050 net/bridge/netfilter/ebtables.c:2160 PGD 1dad2f067 P4D 1dad2f067 PUD 1dad30067 PMD 1b2408067 PTE 0 Oops: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 4249 Comm: syz-executor0 Not tainted 4.16.0-rc3+ #248 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:ebt_size_mwt net/bridge/netfilter/ebtables.c:2037 [inline] RIP: 0010:size_entry_mwt net/bridge/netfilter/ebtables.c:2122 [inline] RIP: 0010:compat_copy_entries+0x49f/0x1050 net/bridge/netfilter/ebtables.c:2160 RSP: 0018:ffff8801b34bf7e8 EFLAGS: 00010246 RAX: 000000000000000a RBX: ffff8801b34bf9d4 RCX: ffffc90001819e4f RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8801b34bf9d8 RBP: ffff8801b34bf968 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff88613340 R11: 0000000000000001 R12: 000000000000ee5f R13: dffffc0000000000 R14: ffff8801b34bf9c8 R15: ffffc90001819e2f FS: 0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000085b9900 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: ffffc90001819e4f CR3: 00000001b2bd7003 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: compat_do_replace+0x398/0x7c0 net/bridge/netfilter/ebtables.c:2249 compat_do_ebt_set_ctl+0x22a/0x2d0 net/bridge/netfilter/ebtables.c:2330 compat_nf_sockopt net/netfilter/nf_sockopt.c:144 [inline] compat_nf_setsockopt+0x88/0x130 net/netfilter/nf_sockopt.c:156 compat_ip_setsockopt+0x8b/0xd0 net/ipv4/ip_sockglue.c:1285 inet_csk_compat_setsockopt+0x95/0x120 net/ipv4/inet_connection_sock.c:1041 compat_tcp_setsockopt+0x3d/0x70 net/ipv4/tcp.c:2916 compat_sock_common_setsockopt+0xb2/0x140 net/core/sock.c:2986 C_SYSC_setsockopt net/compat.c:403 [inline] compat_SyS_setsockopt+0x17c/0x410 net/compat.c:386 do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline] do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 RIP: 0023:0xf7fbbc99 RSP: 002b:00000000ffd5ab8c EFLAGS: 00000286 ORIG_RAX: 000000000000016e RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000 RDX: 0000000000000080 RSI: 0000000020000280 RDI: 0000000000000208 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Code: 8d 4f 20 48 89 c8 48 89 8d c8 fe ff ff 48 c1 e8 03 42 0f b6 14 28 48 89 c8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 b2 0a 00 00 <45> 8b 67 20 44 39 a5 04 ff ff ff 0f 82 bd 08 00 00 e8 cb 52 56 This change addresses the issue, checking that the provided offset are all inside the provided buffer. Fixes: 81e675c227ec ("netfilter: ebtables: add CONFIG_COMPAT support") Reported-and-tested-by: syzbot+5705ba91388d7bc30828@syzkaller.appspotmail.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/bridge/netfilter/ebtables.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)