3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: Guillaume Nault g.nault@alphalink.fr
commit 8540827ebac6b654ab2f69c8fbce9e4fbd6304a0 upstream.
pppoe_rcv() needs to look back at the Ethernet header in order to lookup the PPPoE session. Therefore we need to ensure that the mac header is big enough to contain an Ethernet header. Otherwise eth_hdr(skb)->h_source might access invalid data.
================================================================== BUG: KMSAN: uninit-value in __get_item drivers/net/ppp/pppoe.c:172 [inline] BUG: KMSAN: uninit-value in get_item drivers/net/ppp/pppoe.c:236 [inline] BUG: KMSAN: uninit-value in pppoe_rcv+0xcef/0x10e0 drivers/net/ppp/pppoe.c:450 CPU: 0 PID: 4543 Comm: syz-executor355 Not tainted 4.16.0+ #87 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x185/0x1d0 lib/dump_stack.c:53 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683 __get_item drivers/net/ppp/pppoe.c:172 [inline] get_item drivers/net/ppp/pppoe.c:236 [inline] pppoe_rcv+0xcef/0x10e0 drivers/net/ppp/pppoe.c:450 __netif_receive_skb_core+0x47df/0x4a90 net/core/dev.c:4562 __netif_receive_skb net/core/dev.c:4627 [inline] netif_receive_skb_internal+0x49d/0x630 net/core/dev.c:4701 netif_receive_skb+0x230/0x240 net/core/dev.c:4725 tun_rx_batched drivers/net/tun.c:1555 [inline] tun_get_user+0x740f/0x7c60 drivers/net/tun.c:1962 tun_chr_write_iter+0x1d4/0x330 drivers/net/tun.c:1990 call_write_iter include/linux/fs.h:1782 [inline] new_sync_write fs/read_write.c:469 [inline] __vfs_write+0x7fb/0x9f0 fs/read_write.c:482 vfs_write+0x463/0x8d0 fs/read_write.c:544 SYSC_write+0x172/0x360 fs/read_write.c:589 SyS_write+0x55/0x80 fs/read_write.c:581 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x4447c9 RSP: 002b:00007fff64c8fc28 EFLAGS: 00000297 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004447c9 RDX: 000000000000fd87 RSI: 0000000020000600 RDI: 0000000000000004 RBP: 00000000006cf018 R08: 00007fff64c8fda8 R09: 00007fff00006bda R10: 0000000000005fe7 R11: 0000000000000297 R12: 00000000004020d0 R13: 0000000000402160 R14: 0000000000000000 R15: 0000000000000000
Uninit was created at: kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline] kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314 kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321 slab_post_alloc_hook mm/slab.h:445 [inline] slab_alloc_node mm/slub.c:2737 [inline] __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369 __kmalloc_reserve net/core/skbuff.c:138 [inline] __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206 alloc_skb include/linux/skbuff.h:984 [inline] alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234 sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2085 tun_alloc_skb drivers/net/tun.c:1532 [inline] tun_get_user+0x2242/0x7c60 drivers/net/tun.c:1829 tun_chr_write_iter+0x1d4/0x330 drivers/net/tun.c:1990 call_write_iter include/linux/fs.h:1782 [inline] new_sync_write fs/read_write.c:469 [inline] __vfs_write+0x7fb/0x9f0 fs/read_write.c:482 vfs_write+0x463/0x8d0 fs/read_write.c:544 SYSC_write+0x172/0x360 fs/read_write.c:589 SyS_write+0x55/0x80 fs/read_write.c:581 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 ==================================================================
Fixes: 224cf5ad14c0 ("ppp: Move the PPP drivers") Reported-by: syzbot+f5f6080811c849739212@syzkaller.appspotmail.com Signed-off-by: Guillaume Nault g.nault@alphalink.fr Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/net/ppp/pppoe.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/net/ppp/pppoe.c +++ b/drivers/net/ppp/pppoe.c @@ -426,6 +426,9 @@ static int pppoe_rcv(struct sk_buff *skb if (!skb) goto out;
+ if (skb_mac_header_len(skb) < ETH_HLEN) + goto drop; + if (!pskb_may_pull(skb, sizeof(struct pppoe_hdr))) goto drop;