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    Subject[PATCH 4.19 69/72] net: qrtr: fix a kernel-infoleak in qrtr_recvmsg()
    Date
    From: Eric Dumazet <edumazet@google.com>

    commit 50535249f624d0072cd885bcdce4e4b6fb770160 upstream.

    struct sockaddr_qrtr has a 2-byte hole, and qrtr_recvmsg() currently
    does not clear it before copying kernel data to user space.

    It might be too late to name the hole since sockaddr_qrtr structure is uapi.

    BUG: KMSAN: kernel-infoleak in kmsan_copy_to_user+0x9c/0xb0 mm/kmsan/kmsan_hooks.c:249
    CPU: 0 PID: 29705 Comm: syz-executor.3 Not tainted 5.11.0-rc7-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Call Trace:
    __dump_stack lib/dump_stack.c:79 [inline]
    dump_stack+0x21c/0x280 lib/dump_stack.c:120
    kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118
    kmsan_internal_check_memory+0x202/0x520 mm/kmsan/kmsan.c:402
    kmsan_copy_to_user+0x9c/0xb0 mm/kmsan/kmsan_hooks.c:249
    instrument_copy_to_user include/linux/instrumented.h:121 [inline]
    _copy_to_user+0x1ac/0x270 lib/usercopy.c:33
    copy_to_user include/linux/uaccess.h:209 [inline]
    move_addr_to_user+0x3a2/0x640 net/socket.c:237
    ____sys_recvmsg+0x696/0xd50 net/socket.c:2575
    ___sys_recvmsg net/socket.c:2610 [inline]
    do_recvmmsg+0xa97/0x22d0 net/socket.c:2710
    __sys_recvmmsg net/socket.c:2789 [inline]
    __do_sys_recvmmsg net/socket.c:2812 [inline]
    __se_sys_recvmmsg+0x24a/0x410 net/socket.c:2805
    __x64_sys_recvmmsg+0x62/0x80 net/socket.c:2805
    do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
    entry_SYSCALL_64_after_hwframe+0x44/0xa9
    RIP: 0033:0x465f69
    Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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:00007f43659d6188 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
    RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465f69
    RDX: 0000000000000008 RSI: 0000000020003e40 RDI: 0000000000000003
    RBP: 00000000004bfa8f R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000010060 R11: 0000000000000246 R12: 000000000056bf60
    R13: 0000000000a9fb1f R14: 00007f43659d6300 R15: 0000000000022000

    Local variable ----addr@____sys_recvmsg created at:
    ____sys_recvmsg+0x168/0xd50 net/socket.c:2550
    ____sys_recvmsg+0x168/0xd50 net/socket.c:2550

    Bytes 2-3 of 12 are uninitialized
    Memory access of size 12 starts at ffff88817c627b40
    Data copied to user address 0000000020000140

    Fixes: bdabad3e363d ("net: Add Qualcomm IPC router")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Courtney Cavin <courtney.cavin@sonymobile.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/qrtr/qrtr.c | 5 +++++
    1 file changed, 5 insertions(+)

    --- a/net/qrtr/qrtr.c
    +++ b/net/qrtr/qrtr.c
    @@ -868,6 +868,11 @@ static int qrtr_recvmsg(struct socket *s
    rc = copied;

    if (addr) {
    + /* There is an anonymous 2-byte hole after sq_family,
    + * make sure to clear it.
    + */
    + memset(addr, 0, sizeof(*addr));
    +
    cb = (struct qrtr_cb *)skb->cb;
    addr->sq_family = AF_QIPCRTR;
    addr->sq_node = cb->src_node;

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