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    Subject[PATCH 3.16 164/245] macvlan: do not assume mac_header is set in macvlan_broadcast()
    3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Dumazet <edumazet@google.com>

    commit 96cc4b69581db68efc9749ef32e9cf8e0160c509 upstream.

    Use of eth_hdr() in tx path is error prone.

    Many drivers call skb_reset_mac_header() before using it,
    but others do not.

    Commit 6d1ccff62780 ("net: reset mac header in dev_start_xmit()")
    attempted to fix this generically, but commit d346a3fae3ff
    ("packet: introduce PACKET_QDISC_BYPASS socket option") brought
    back the macvlan bug.

    Lets add a new helper, so that tx paths no longer have
    to call skb_reset_mac_header() only to get a pointer
    to skb->data.

    Hopefully we will be able to revert 6d1ccff62780
    ("net: reset mac header in dev_start_xmit()") and save few cycles
    in transmit fast path.

    BUG: KASAN: use-after-free in __get_unaligned_cpu32 include/linux/unaligned/packed_struct.h:19 [inline]
    BUG: KASAN: use-after-free in mc_hash drivers/net/macvlan.c:251 [inline]
    BUG: KASAN: use-after-free in macvlan_broadcast+0x547/0x620 drivers/net/macvlan.c:277
    Read of size 4 at addr ffff8880a4932401 by task syz-executor947/9579

    CPU: 0 PID: 9579 Comm: syz-executor947 Not tainted 5.5.0-rc4-syzkaller #0
    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+0x197/0x210 lib/dump_stack.c:118
    print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
    __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
    kasan_report+0x12/0x20 mm/kasan/common.c:639
    __asan_report_load_n_noabort+0xf/0x20 mm/kasan/generic_report.c:145
    __get_unaligned_cpu32 include/linux/unaligned/packed_struct.h:19 [inline]
    mc_hash drivers/net/macvlan.c:251 [inline]
    macvlan_broadcast+0x547/0x620 drivers/net/macvlan.c:277
    macvlan_queue_xmit drivers/net/macvlan.c:520 [inline]
    macvlan_start_xmit+0x402/0x77f drivers/net/macvlan.c:559
    __netdev_start_xmit include/linux/netdevice.h:4447 [inline]
    netdev_start_xmit include/linux/netdevice.h:4461 [inline]
    dev_direct_xmit+0x419/0x630 net/core/dev.c:4079
    packet_direct_xmit+0x1a9/0x250 net/packet/af_packet.c:240
    packet_snd net/packet/af_packet.c:2966 [inline]
    packet_sendmsg+0x260d/0x6220 net/packet/af_packet.c:2991
    sock_sendmsg_nosec net/socket.c:639 [inline]
    sock_sendmsg+0xd7/0x130 net/socket.c:659
    __sys_sendto+0x262/0x380 net/socket.c:1985
    __do_sys_sendto net/socket.c:1997 [inline]
    __se_sys_sendto net/socket.c:1993 [inline]
    __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1993
    do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
    entry_SYSCALL_64_after_hwframe+0x49/0xbe
    RIP: 0033:0x442639
    Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 5b 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
    RSP: 002b:00007ffc13549e08 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
    RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000442639
    RDX: 000000000000000e RSI: 0000000020000080 RDI: 0000000000000003
    RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
    R13: 0000000000403bb0 R14: 0000000000000000 R15: 0000000000000000

    Allocated by task 9389:
    save_stack+0x23/0x90 mm/kasan/common.c:72
    set_track mm/kasan/common.c:80 [inline]
    __kasan_kmalloc mm/kasan/common.c:513 [inline]
    __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486
    kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527
    __do_kmalloc mm/slab.c:3656 [inline]
    __kmalloc+0x163/0x770 mm/slab.c:3665
    kmalloc include/linux/slab.h:561 [inline]
    tomoyo_realpath_from_path+0xc5/0x660 security/tomoyo/realpath.c:252
    tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
    tomoyo_path_perm+0x230/0x430 security/tomoyo/file.c:822
    tomoyo_inode_getattr+0x1d/0x30 security/tomoyo/tomoyo.c:129
    security_inode_getattr+0xf2/0x150 security/security.c:1222
    vfs_getattr+0x25/0x70 fs/stat.c:115
    vfs_statx_fd+0x71/0xc0 fs/stat.c:145
    vfs_fstat include/linux/fs.h:3265 [inline]
    __do_sys_newfstat+0x9b/0x120 fs/stat.c:378
    __se_sys_newfstat fs/stat.c:375 [inline]
    __x64_sys_newfstat+0x54/0x80 fs/stat.c:375
    do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

    Freed by task 9389:
    save_stack+0x23/0x90 mm/kasan/common.c:72
    set_track mm/kasan/common.c:80 [inline]
    kasan_set_free_info mm/kasan/common.c:335 [inline]
    __kasan_slab_free+0x102/0x150 mm/kasan/common.c:474
    kasan_slab_free+0xe/0x10 mm/kasan/common.c:483
    __cache_free mm/slab.c:3426 [inline]
    kfree+0x10a/0x2c0 mm/slab.c:3757
    tomoyo_realpath_from_path+0x1a7/0x660 security/tomoyo/realpath.c:289
    tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
    tomoyo_path_perm+0x230/0x430 security/tomoyo/file.c:822
    tomoyo_inode_getattr+0x1d/0x30 security/tomoyo/tomoyo.c:129
    security_inode_getattr+0xf2/0x150 security/security.c:1222
    vfs_getattr+0x25/0x70 fs/stat.c:115
    vfs_statx_fd+0x71/0xc0 fs/stat.c:145
    vfs_fstat include/linux/fs.h:3265 [inline]
    __do_sys_newfstat+0x9b/0x120 fs/stat.c:378
    __se_sys_newfstat fs/stat.c:375 [inline]
    __x64_sys_newfstat+0x54/0x80 fs/stat.c:375
    do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

    The buggy address belongs to the object at ffff8880a4932000
    which belongs to the cache kmalloc-4k of size 4096
    The buggy address is located 1025 bytes inside of
    4096-byte region [ffff8880a4932000, ffff8880a4933000)
    The buggy address belongs to the page:
    page:ffffea0002924c80 refcount:1 mapcount:0 mapping:ffff8880aa402000 index:0x0 compound_mapcount: 0
    raw: 00fffe0000010200 ffffea0002846208 ffffea00028f3888 ffff8880aa402000
    raw: 0000000000000000 ffff8880a4932000 0000000100000001 0000000000000000
    page dumped because: kasan: bad access detected

    Memory state around the buggy address:
    ffff8880a4932300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8880a4932380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    >ffff8880a4932400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ^
    ffff8880a4932480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8880a4932500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

    Fixes: b863ceb7ddce ("[NET]: Add macvlan driver")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    [bwh: Backported to 3.16: adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/net/macvlan.c | 2 +-
    include/linux/if_ether.h | 8 ++++++++
    2 files changed, 9 insertions(+), 1 deletion(-)

    --- a/drivers/net/macvlan.c
    +++ b/drivers/net/macvlan.c
    @@ -162,7 +162,7 @@ static void macvlan_broadcast(struct sk_
    struct net_device *src,
    enum macvlan_mode mode)
    {
    - const struct ethhdr *eth = eth_hdr(skb);
    + const struct ethhdr *eth = skb_eth_hdr(skb);
    const struct macvlan_dev *vlan;
    struct sk_buff *nskb;
    unsigned int i;
    --- a/include/linux/if_ether.h
    +++ b/include/linux/if_ether.h
    @@ -28,6 +28,14 @@ static inline struct ethhdr *eth_hdr(con
    return (struct ethhdr *)skb_mac_header(skb);
    }

    +/* Prefer this version in TX path, instead of
    + * skb_reset_mac_header() + eth_hdr()
    + */
    +static inline struct ethhdr *skb_eth_hdr(const struct sk_buff *skb)
    +{
    + return (struct ethhdr *)skb->data;
    +}
    +
    int eth_header_parse(const struct sk_buff *skb, unsigned char *haddr);

    extern ssize_t sysfs_format_mac(char *buf, const unsigned char *addr, int len);
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