| From: Eric Dumazet <edumazet@google.com> |
| Date: Wed, 29 May 2019 15:36:10 -0700 |
| Subject: net-gro: fix use-after-free read in napi_gro_frags() |
| |
| commit a4270d6795b0580287453ea55974d948393e66ef upstream. |
| |
| If a network driver provides to napi_gro_frags() an |
| skb with a page fragment of exactly 14 bytes, the call |
| to gro_pull_from_frag0() will 'consume' the fragment |
| by calling skb_frag_unref(skb, 0), and the page might |
| be freed and reused. |
| |
| Reading eth->h_proto at the end of napi_frags_skb() might |
| read mangled data, or crash under specific debugging features. |
| |
| BUG: KASAN: use-after-free in napi_frags_skb net/core/dev.c:5833 [inline] |
| BUG: KASAN: use-after-free in napi_gro_frags+0xc6f/0xd10 net/core/dev.c:5841 |
| Read of size 2 at addr ffff88809366840c by task syz-executor599/8957 |
| |
| CPU: 1 PID: 8957 Comm: syz-executor599 Not tainted 5.2.0-rc1+ #32 |
| Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 |
| Call Trace: |
| __dump_stack lib/dump_stack.c:77 [inline] |
| dump_stack+0x172/0x1f0 lib/dump_stack.c:113 |
| print_address_description.cold+0x7c/0x20d mm/kasan/report.c:188 |
| __kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317 |
| kasan_report+0x12/0x20 mm/kasan/common.c:614 |
| __asan_report_load_n_noabort+0xf/0x20 mm/kasan/generic_report.c:142 |
| napi_frags_skb net/core/dev.c:5833 [inline] |
| napi_gro_frags+0xc6f/0xd10 net/core/dev.c:5841 |
| tun_get_user+0x2f3c/0x3ff0 drivers/net/tun.c:1991 |
| tun_chr_write_iter+0xbd/0x156 drivers/net/tun.c:2037 |
| call_write_iter include/linux/fs.h:1872 [inline] |
| do_iter_readv_writev+0x5f8/0x8f0 fs/read_write.c:693 |
| do_iter_write fs/read_write.c:970 [inline] |
| do_iter_write+0x184/0x610 fs/read_write.c:951 |
| vfs_writev+0x1b3/0x2f0 fs/read_write.c:1015 |
| do_writev+0x15b/0x330 fs/read_write.c:1058 |
| |
| Fixes: a50e233c50db ("net-gro: restore frag0 optimization") |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Reported-by: syzbot <syzkaller@googlegroups.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| net/core/dev.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/net/core/dev.c |
| +++ b/net/core/dev.c |
| @@ -4239,7 +4239,6 @@ static struct sk_buff *napi_frags_skb(st |
| skb_reset_mac_header(skb); |
| skb_gro_reset_offset(skb); |
| |
| - eth = skb_gro_header_fast(skb, 0); |
| if (unlikely(skb_gro_header_hard(skb, hlen))) { |
| eth = skb_gro_header_slow(skb, hlen, 0); |
| if (unlikely(!eth)) { |
| @@ -4247,6 +4246,7 @@ static struct sk_buff *napi_frags_skb(st |
| return NULL; |
| } |
| } else { |
| + eth = (const struct ethhdr *)skb->data; |
| gro_pull_from_frag0(skb, hlen); |
| NAPI_GRO_CB(skb)->frag0 += hlen; |
| NAPI_GRO_CB(skb)->frag0_len -= hlen; |