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    Subject[PATCH 4.4 014/133] igmp: Add ip_mc_list lock in ip_check_mc_rcu
    Date
    From: Liu Jian <liujian56@huawei.com>

    commit 23d2b94043ca8835bd1e67749020e839f396a1c2 upstream.

    I got below panic when doing fuzz test:

    Kernel panic - not syncing: panic_on_warn set ...
    CPU: 0 PID: 4056 Comm: syz-executor.3 Tainted: G B 5.14.0-rc1-00195-gcff5c4254439-dirty #2
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
    Call Trace:
    dump_stack_lvl+0x7a/0x9b
    panic+0x2cd/0x5af
    end_report.cold+0x5a/0x5a
    kasan_report+0xec/0x110
    ip_check_mc_rcu+0x556/0x5d0
    __mkroute_output+0x895/0x1740
    ip_route_output_key_hash_rcu+0x2d0/0x1050
    ip_route_output_key_hash+0x182/0x2e0
    ip_route_output_flow+0x28/0x130
    udp_sendmsg+0x165d/0x2280
    udpv6_sendmsg+0x121e/0x24f0
    inet6_sendmsg+0xf7/0x140
    sock_sendmsg+0xe9/0x180
    ____sys_sendmsg+0x2b8/0x7a0
    ___sys_sendmsg+0xf0/0x160
    __sys_sendmmsg+0x17e/0x3c0
    __x64_sys_sendmmsg+0x9e/0x100
    do_syscall_64+0x3b/0x90
    entry_SYSCALL_64_after_hwframe+0x44/0xae
    RIP: 0033:0x462eb9
    Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
    RSP: 002b:00007f3df5af1c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
    RAX: ffffffffffffffda RBX: 000000000073bf00 RCX: 0000000000462eb9
    RDX: 0000000000000312 RSI: 0000000020001700 RDI: 0000000000000007
    RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3df5af26bc
    R13: 00000000004c372d R14: 0000000000700b10 R15: 00000000ffffffff

    It is one use-after-free in ip_check_mc_rcu.
    In ip_mc_del_src, the ip_sf_list of pmc has been freed under pmc->lock protection.
    But access to ip_sf_list in ip_check_mc_rcu is not protected by the lock.

    Signed-off-by: Liu Jian <liujian56@huawei.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Lee Jones <lee.jones@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/igmp.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/net/ipv4/igmp.c
    +++ b/net/ipv4/igmp.c
    @@ -2631,6 +2631,7 @@ int ip_check_mc_rcu(struct in_device *in
    rv = 1;
    } else if (im) {
    if (src_addr) {
    + spin_lock_bh(&im->lock);
    for (psf = im->sources; psf; psf = psf->sf_next) {
    if (psf->sf_inaddr == src_addr)
    break;
    @@ -2641,6 +2642,7 @@ int ip_check_mc_rcu(struct in_device *in
    im->sfcount[MCAST_EXCLUDE];
    else
    rv = im->sfcount[MCAST_EXCLUDE] != 0;
    + spin_unlock_bh(&im->lock);
    } else
    rv = 1; /* unspecified source; tentatively allow */
    }

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